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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Oct. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3
Trading Symbol	KOP
Entity Registrant Name	Koppers Holdings Inc.
Entity Central Index Key	0001315257
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		20,662,903

Condensed Consolidated Statement of Operations and Comprehensive Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Net sales	$ 371.1	$ 433.8	$ 1,103.0	$ 1,263.2
Cost of sales (excluding items below)	294.1	359.1	886.4	1,059.4
Depreciation and amortization	13.8	15.5	42.0	45.2
Gain on sale of business	(2.1)	0.0	(2.1)	(3.2)
Impairment and restructuring charges	5.0	1.4	16.1	7.1
Selling, general and administrative expenses	32.6	30.8	93.1	93.7
Operating profit	27.7	27.0	67.5	61.0
Other income	0.2	0.0	2.2	0.4
Interest expense	11.7	12.6	38.3	38.5
Income before income taxes	16.2	14.4	31.4	22.9
Income tax provision	4.2	5.2	10.5	10.0
Income from continuing operations	12.0	9.2	20.9	12.9
(Loss) income from discontinued operations, net of tax expense of $0.0, $0.0, $0.3 and $0.0	(0.1)	(0.1)	0.5	(0.1)
Net income	11.9	9.1	21.4	12.8
Net loss attributable to noncontrolling interests	(0.2)	(1.0)	(1.5)	(2.9)
Net income attributable to Koppers	$ 12.1	$ 10.1	$ 22.9	$ 15.7
Basic -
Continuing operations	$ 0.59	$ 0.49	$ 1.08	$ 0.77
Discontinued operations	0.00	0.00	0.03	0.00
Earnings per basic common share	0.59	0.49	1.11	0.77
Diluted -
Continuing operations	0.58	0.49	1.07	0.76
Discontinued operations	0.00	0.00	0.02	0.00
Earnings per diluted common share	$ 0.58	$ 0.49	$ 1.09	$ 0.76
Comprehensive income (loss)	$ 14.1	$ (4.7)	$ 31.4	$ (7.9)
Comprehensive loss attributable to noncontrolling interests	(0.2)	(1.2)	(1.7)	(3.1)
Comprehensive income (loss) attributable to Koppers	$ 14.3	$ (3.5)	$ 33.1	$ (4.8)
Weighted average shares outstanding (in thousands):
Basic	20,657	20,553	20,627	20,537
Diluted	21,163	20,632	20,975	20,609

Condensed Consolidated Statement of Operations and Comprehensive Income (Loss) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Income from discontinued operations, tax expense	$ 0.0	$ 0.0	$ 0.3	$ 0.0

- Definition

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

+ References + Details

Condensed Consolidated Balance Sheet - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 17.7	$ 21.8
Accounts receivable, net of allowance of $4.6 and $6.5	171.3	155.0
Income tax receivable	0.1	4.6
Inventories, net	216.2	226.4
Loan to related party	9.5	9.5
Other current assets	30.2	27.0
Total current assets	445.0	444.3
Property, plant and equipment, net	277.2	277.8
Goodwill	187.8	186.6
Intangible assets, net	146.5	156.1
Deferred tax assets	33.7	36.6
Other assets	10.6	11.5
Total assets	1,100.8	1,112.9
Liabilities
Accounts payable	141.9	140.8
Accrued liabilities	102.4	99.8
Current maturities of long-term debt	39.5	39.9
Total current liabilities	283.8	280.5
Long-term debt	642.0	682.4
Accrued postretirement benefits	51.5	53.6
Deferred tax liabilities	6.0	5.7
Other long-term liabilities	92.8	103.1
Total liabilities	1,076.1	1,125.3
Commitments and contingent liabilities (Note 18)
Equity
Senior Convertible Preferred Stock, $0.01 par value per share; 10,000,000 shares authorized; no shares issued	0.0	0.0
Common Stock, $0.01 par value per share; 80,000,000 shares authorized; 22,138,073 and 22,015,994 shares issued	0.2	0.2
Additional paid-in capital	173.8	167.8
Accumulated deficit	(31.1)	(54.0)
Accumulated other comprehensive loss	(69.6)	(79.8)
Treasury stock, at cost, 1,475,170 and 1,459,164 shares	(53.0)	(52.7)
Total Koppers shareholders’ equity (deficit)	20.3	(18.5)
Noncontrolling interests	4.4	6.1
Total equity (deficit)	24.7	(12.4)
Total liabilities and equity (deficit)	$ 1,100.8	$ 1,112.9

Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Accounts receivable, allowance	$ 4.6	$ 6.5
Senior Convertible Preferred Stock, par value	$ 0.01	$ 0.01
Senior Convertible Preferred Stock, shares authorized	10,000,000	10,000,000
Senior Convertible Preferred Stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	80,000,000	80,000,000
Common Stock, shares issued	22,138,073	22,015,994
Treasury stock, shares	1,475,170	1,459,164

Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash provided by (used in) operating activities:
Net income	$ 21.4	$ 12.8
Adjustments to reconcile net cash provided by operating activities:
Depreciation and amortization	42.0	45.2
Impairment charges	3.5	7.1
Gain on sale of business	(2.1)	(3.2)
Deferred income taxes	(0.5)	(0.8)
Equity loss, net of dividends received	1.0	2.2
Change in other liabilities	(7.6)	(3.8)
Non-cash interest expense	4.8	2.7
Stock-based compensation	5.7	3.1
Deferred revenue	(1.4)	28.3
Other	4.7	1.7
Changes in working capital:
Accounts receivable	(17.9)	(8.8)
Inventories	13.8	13.7
Accounts payable	0.9	34.2
Accrued liabilities	15.4	(30.0)
Other working capital	(1.2)	(9.3)
Net cash provided by operating activities	82.5	95.1
Cash (used in) provided by investing activities:
Capital expenditures	(32.2)	(26.4)
Acquisitions, net of cash acquired	0.0	(15.3)
Net cash (used in) provided by divestitures and asset sales	(4.5)	14.7
Net cash used in investing activities	(36.7)	(27.0)
Cash provided by (used in) financing activities:
Borrowings of revolving credit	457.9	465.4
Repayments of revolving credit	(477.9)	(531.0)
Borrowings of long-term debt	0.0	1.8
Repayments of long-term debt	(23.4)	(22.5)
Issuances of Common Stock	0.5	0.0
Repurchases of Common Stock	(0.3)	(0.3)
Payment of deferred financing costs	(1.4)	(1.0)
Dividends paid	0.0	(8.7)
Net cash used in financing activities	(44.6)	(96.3)
Effect of exchange rate changes on cash	(5.3)	10.1
Net decrease in cash and cash equivalents	(4.1)	(18.1)
Cash and cash equivalents at beginning of period	21.8	51.1
Cash and cash equivalents at end of period	$ 17.7	$ 33.0

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. Basis of Presentation The accompanying unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States applicable to interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation of Koppers Holdings Inc.’s and its subsidiaries’ (“Koppers”, “Koppers Holdings” or the “Company”) financial position and interim results as of and for the periods presented have been included. All such adjustments are of a normal recurring nature unless disclosed otherwise. Because the Company’s business is seasonal, results for interim periods are not necessarily indicative of those that may be expected for a full year. The Condensed Consolidated Balance Sheet for December 31, 2015 has been summarized from the audited balance sheet contained in the Annual Report on Form 10-K for the year ended December 31, 2015. Certain prior period amounts in the notes to the consolidated financial statements have been reclassified to conform to the current period’s presentation. The financial information included herein should be read in conjunction with the Company’s audited consolidated financial statements and related notes included in its Annual Report on Form 10-K for the year ended December 31, 2015.

New Accounting Pronouncements	9 Months Ended
New Accounting Pronouncements	Sep. 30, 2016
Accounting Changes And Error Corrections [Abstract]
New Accounting Pronouncements	2. New Accounting Pronouncements In August 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” The update amends the guidance in Accounting Standards Codification 230, Statement of Cash Flows, and clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows with the objective of reducing the existing diversity in practice related to eight specific cash flow issues. The amendments in this update are effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company is in the process of assessing the impact the adoption of this ASU will have on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09, “Improvements to Employee Share-Based Payment Accounting.” This ASU makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The amendments in this ASU are effective for annual periods beginning after December 15, 2016 and for the interim periods therein. The Company does not expect the adoption of this ASU will have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-08, “Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” that amends the principal versus agent guidance in ASU 2014-09. ASU 2016-08 clarifies that the analysis must focus on whether the entity has control of the goods or services before they are transferred to the customer. ASU 2016-08 also provides additional guidance about how to apply the control principle when services are provided and when goods or services are combined with other goods or services. The effective date of the standard for the Company will coincide with the effective date of ASU 2014-09 on January 1, 2018. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” ASU 2016-02 requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than one year. Recognition, measurement and presentation of expenses will depend on classification as a finance or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The standard is effective January 1, 2019 and early adoption is permitted. The guidance requires a modified retrospective adoption. The Company is currently evaluating the impact of the adoption of ASU 2016-02 will have on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs,” which requires companies to present debt issuance costs associated with a debt liability as a deduction from the carrying amount of that debt liability on the balance sheet rather than being capitalized as an asset. The standard is effective for interim and annual periods beginning after December 15, 2015, and retrospective presentation is required. The Company adopted this guidance as of January 1, 2016, which resulted in $9.5 million and $12.5 million of debt issuance costs being reclassified from other assets to long-term debt as of September 30, 2016 and December 31, 2015, respectively. In February 2015, the FASB issued ASU No. 2015-02, “Consolidation (Topic 810): Amendments to the Consolidation Analysis,” which provides consolidation guidance that entities must use to evaluate specific ownership and contractual arrangements that lead to a consolidation conclusion. The updates could change consolidation outcomes affecting presentation and disclosures. The Company adopted this guidance as of January 1, 2016, which did not have a material effect on the Company’s financial statements. In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 requires an entity to recognize revenue in a manner that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. An entity can either adopt this amendment retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the update recognized at the date of initial application. This guidance will be effective January 1, 2018. The Company is currently evaluating the impact of the adoption of ASU 2014-09 on the Company’s financial statements.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

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+ Details

Plant Closures and Divestitures

9 Months Ended

Sep. 30, 2016

Discontinued Operations And Disposal Groups [Abstract]

Plant Closures and Divestitures

3. Plant Closures and Divestitures

On October 24, 2016, the Company agreed to a long-term lease of its wood treatment facility in Houston, Texas to a third party. This facility, owned by the Company’s wholly-owned subsidiary, Wood Protection L.P., is engaged in the manufacturing and sale of pressure-treated dimensional lumber and had revenue of approximately $8 million for the nine months ended September 30, 2016 and $14 million for the year ended December 31, 2015.

In March 2016, the Company discontinued production at its 60-percent owned Carbon Materials and Chemicals (“CMC”) plant located in Tangshan, China. The Company’s 60-percent owned subsidiary, Koppers (China) Carbon & Chemical Company Limited (“KCCC”) is located adjacent to a metallurgical coke facility owned by KCCC’s minority partner, which also closed. The KCCC plant relied on the coke facility for a significant portion of raw material supply, utilities and other shared services. In 2015, the Company recorded a severance charge of $0.9 million. For the nine months ended September 30, 2016, the Company has recorded inventory write-down charges of $0.7 million in connection with the facility.

In February 2016, the Company announced plans, which were approved by management and the board in December 2015, to cease coal tar distillation operations at both of its United Kingdom CMC facilities. Accordingly, the Company recorded environmental charges, asset retirement obligations and fixed asset impairment charges totaling $13.9 million during the year ended December 31, 2015. For the nine months ended September 30, 2016, the Company recorded severance charges of $1.7 million. In July 2016, the Company sold substantially all of its CMC tar distillation properties and assets in the United Kingdom. In exchange, the Company transferred cash to the buyer and the buyer assumed historical environmental and asset retirement obligations. The Company recognized a gain of $2.1 million on this transaction. This gain is reported in “Gain on sale of business” on the Condensed Consolidated Statement of Operations and Comprehensive Income (Loss).

In January 2016, the Company announced its decision, which was approved by management and the board in December 2015, to discontinue coal tar distillation activities at its CMC plant located in Clairton, Pennsylvania. Accordingly, the Company recorded severance, inventory write-down, asset retirement obligation and fixed asset impairment charges totaling $18.8 million during the year ended December 31, 2015. For the three and nine months ended September 30, 2016, the Company recorded an additional asset retirement obligation and fixed asset impairment charges totaling $3.8 and $4.8 million, respectively. Coal tar distillation activities at Clairton were substantially discontinued at the end of July 2016. As of September 30, 2016, all depreciable fixed assets directly related to the facility have been impaired.

In August 2015, the Company closed its Railroad and Utility Products and Services (“RUPS”) plant located in Green Spring, West Virginia. Accordingly, the Company recorded severance, asset retirement obligation and fixed asset impairment charges of $5.7 million during the year ended December 31, 2015. For the three and nine months ended September 30, 2016, the Company has recorded additional asset retirement obligation charges of $0.4 and $2.3 million, respectively, in connection with the closure of the facility. As of September 30, 2016, the facility is closed.

In January 2015, Koppers Inc. sold its RUPS North American utility pole business for cash of $12.3 million and a promissory note of $1.3 million. The Company recognized a gain of $3.2 million on this transaction in 2015. The promissory note is repayable in three remaining equal annual installments. This gain is reported in “Gain on sale of business” on the Condensed Consolidated Statement of Operations and Comprehensive Income (Loss). The proceeds of the sale are reported within “Net cash proceeds from divestitures and asset sales” on the Condensed Consolidated Statement of Cash Flows. For the three and nine months ended September 30, 2016, the Company has recorded asset retirement obligation charges of $0.9 and $2.4 million, respectively, in connection with assets that were associated with this business line.

In April 2014, the Company ceased its coal tar distillation activities at its CMC facility located in Uithoorn, the Netherlands. In the second quarter of 2016, the Company recorded a $3.7 million net present value accrual related to future real estate lease obligations, net of estimated sublease revenue, at the closed site. The Company determined that it met the cease-use criteria required for the accrual of these costs upon the completion of site demolition in April 2016.

Details of the restructuring activities and related reserves are as follows:

	Severance and employee benefits			Environmental remediation			Site demolition			Other			Total
(Dollars in millions)
Reserve at December 31, 2014	$	0.0		$	4.1		$	3.9		$	0.1		$	8.1
Accrual		2.2			0.6			13.7			1.3			17.8
Cost charged against assets		0.0			0.0			0.0			(1.3	)		(1.3	)
Reversal of accrued charges		0.0			0.0			(0.3	)		0.0			(0.3	)
Cash paid		(0.2	)		0.0			(4.8	)		(0.1	)		(5.1	)
Currency translation		0.0			(0.4	)		(0.3	)		0.0			(0.7	)
Reserve at December 31, 2015	$	2.0		$	4.3		$	12.2		$	0.0		$	18.5
Accrual		2.1			0.0			4.8			4.4			11.3
Cost charged against assets		0.0			0.0			0.0			(0.7	)		(0.7	)
Reversal of accrued charges		(1.8	)		(0.5	)		(8.4	)		(0.1	)		(10.8	)
Cash paid		(1.1	)		(1.5	)		(5.8	)		0.0			(8.4	)
Currency translation		(0.1	)		0.1			(0.7	)		0.0			(0.7	)
Reserve at September 30, 2016	$	1.1		$	2.4		$	2.1		$	3.6		$	9.2

- Definition

The entire disclosure related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

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+ Details

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2016
Related Party Transactions [Abstract]
Related Party Transactions	4. Related Party Transactions As of September 30, 2016, the Company has loaned $9.5 million to Tangshan Koppers Kailuan Carbon Chemical Company Limited (“TKK”), a 30-percent owned company in China. The loan was repayable in six equal monthly installments beginning in June 2015. TKK defaulted on the first installment payment of $1.6 million due in June 2015 and each monthly payment thereafter. The Company has tentatively agreed to terms with TKK’s controlling shareholder regarding repayment of the loan in addition to the potential sale of the Company’s 30-percent interest in TKK. The Company recognized an equity loss from TKK of $0.3 million and $1.0 million for the three and nine months ended September 30, 2016. As of September 30, 2016, management has concluded that it is probable that the full principal amount of the loan remains collectible, and accordingly, no provision has been recorded.

Fair Value Measurements

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. Fair Value Measurements

Carrying amounts and the related estimated fair values of the Company’s financial instruments as of September 30, 2016 and December 31, 2015 are as follows:

	September 30, 2016				December 31, 2015
	Fair Value		Carrying Value		Fair Value		Carrying Value
(Dollars in millions)
Financial assets:
Cash and cash equivalents, including restricted cash	$	17.7	$	17.7	$	21.8	$	21.8
Investments and other assets^(a)		1.1		1.1		1.1		1.1
Financial liabilities:
Long-term debt (including current portion)	$	691.0	$	681.5	$	724.6	$	722.3

(a)	Excludes equity method investments.

Cash and cash equivalents – The carrying amount approximates fair value because of the short maturity of those instruments.

Investments and other assets – Represents the broker-quoted cash surrender value on universal life insurance policies. This asset is classified as Level 2 in the valuation hierarchy and is measured from values received from financial institutions.

Debt – The fair value of the Company’s long-term debt is estimated based on the market prices for the same or similar issues or on the current rates offered to the Company for debt of the same remaining maturities (Level 2). The fair values of the term loan and revolving credit facility approximate carrying value due to the variable rate nature of these instruments.

Comprehensive Income (Loss) and Equity (Deficit)

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Comprehensive Income (Loss) and Equity (Deficit)

6. Comprehensive Income (Loss) and Equity (Deficit)

Total comprehensive income (loss) for the three and nine months ended September 30, 2016 and 2015 is summarized in the table below:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Net income	$	11.9		$	9.1		$	21.4		$	12.8
Other comprehensive income (loss):
Change in currency translation adjustment		0.7			(13.6	)		4.1			(21.9	)
Change in unrealized gains (losses) on cash flow hedges, net of tax (expense) benefit of $(1.0), $0.5, $(3.4) and $0.8		1.7			(1.2	)		5.5			(1.7	)
Change in unrecognized pension net income, net of tax (expense) benefit of $(0.1), $(0.7), $(0.4) and $(2.0)		(0.2	)		1.0			0.4			3.0
Change in unrecognized prior service cost		0.0			0.0			0.0			(0.1	)
Total comprehensive income (loss)		14.1			(4.7	)		31.4			(7.9	)
Less: Comprehensive loss attributable to noncontrolling interests		(0.2	)		(1.2	)		(1.7	)		(3.1	)
Comprehensive income (loss) attributable to Koppers	$	14.3		$	(3.5	)	$	33.1		$	(4.8	)

Amounts reclassified from accumulated other comprehensive loss to net income consist of amounts shown for changes in unrecognized pension net loss and unrecognized prior service cost. These components of accumulated other comprehensive income are included in the computation of net periodic pension cost as disclosed in Note 13 – Pensions and Postretirement Benefit Plans. Other amounts reclassified from accumulated other comprehensive income include losses related to derivative financial instruments, net of tax, of $1.6 million and $4.8 million for the three and nine months ended September 30, 2016, respectively and $1.8 million and $3.7 million for the three and nine months ended September 30, 2015, respectively.

The following tables present the change in equity (deficit) for the nine months ended September 30, 2016 and 2015, respectively:

(Dollars in millions)	Total Koppers Shareholders’ Equity (Deficit)			Noncontrolling Interests			Total Equity (Deficit)
Balance at December 31, 2015	$	(18.5	)	$	6.1		$	(12.4	)
Net income (loss)		22.9			(1.5	)		21.4
Employee stock plans		6.0			0.0			6.0
Other comprehensive income		10.2			(0.2	)		10.0
Repurchases of common stock		(0.3	)		0.0			(0.3	)
Balance at September 30, 2016	$	20.3		$	4.4		$	24.7

(Dollars in millions)	Total Koppers Shareholders’ Equity			Noncontrolling Interests			Total Equity
Balance at December 31, 2014	$	70.0		$	13.9		$	83.9
Net income (loss)		15.7			(2.9	)		12.8
Employee stock plans		3.1			0.0			3.1
Other comprehensive loss		(20.5	)		(0.2	)		(20.7	)
Dividends		0.0			(3.5	)		(3.5	)
Repurchases of common stock		(0.3	)		0.0			(0.3	)
Balance at September 30, 2015	$	68.0		$	7.3		$	75.3

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 5
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e))
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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-Paragraph 1
-Subparagraph (SX 210.5-02(31))
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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-Subparagraph (SAB Topic 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

+ Details

Earnings per Common Share

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Earnings per Common Share

7. Earnings per Common Share

The computation of basic earnings per common share for the periods presented is based upon the weighted average number of common shares outstanding during the periods. The computation of diluted earnings per common share includes the effect of non-vested nonqualified stock options and restricted stock units assuming such options and stock units were outstanding common shares at the beginning of the period. The effect of antidilutive securities is excluded from the computation of diluted loss per common share, if any.

The following table sets forth the computation of basic and diluted earnings per common share:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016		2015
(Dollars in millions, except share amounts, in thousands, and per share amounts)
Net income attributable to Koppers	$	12.1		$	10.1		$	22.9	$	15.7
Less: (Loss) income from discontinued operations		(0.1	)		(0.1	)		0.5		(0.1	)
Income from continuing operations attributable to Koppers	$	12.2		$	10.2		$	22.4	$	15.8
Weighted average common shares outstanding:
Basic		20,657			20,553			20,627		20,537
Effect of dilutive securities		506			79			348		72
Diluted		21,163			20,632			20,975		20,609
Income per common share – continuing operations:
Basic income per common share	$	0.59		$	0.49		$	1.08	$	0.77
Diluted income per common share		0.58			0.49			1.07		0.76
Other data:
Antidilutive securities excluded from computation of diluted earnings per common share		339			738			421		671

Stock-based Compensation

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

8. Stock-based Compensation

The amended and restated 2005 Long-Term Incentive Plan (the “LTIP”) provides for the grant to eligible persons of stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance awards, dividend equivalents and other stock-based awards, which are collectively referred to as the awards.

Restricted Stock Units and Performance Stock Units

Under the LTIP, the board of directors granted restricted stock units and performance stock units to certain employee participants (collectively, the “stock units”). For grants to employees prior to 2015, restricted stock units vest on the third anniversary of the grant date, assuming continued employment by the participant. For the March 2015 and 2016 grants to employees, the restricted stock units vest in four equal annual installments. Restricted stock units that have one-year vesting periods are also issued under the LTIP to members of the board of directors in connection with annual director compensation and, from time to time, are issued to members of management in connection with employee compensation with varying vesting periods.

Compensation expense for non-vested stock units is recorded over the vesting period based on the fair value at the date of grant. The fair value of restricted stock units and performance stock units with a performance condition is the market price of the underlying common stock on the date of grant.

Performance stock units granted prior to 2016 vest based upon a performance condition. These performance stock units generally have three-year performance objectives and all performance stock units have a three-year period for vesting (if the applicable performance objective is achieved). For awards granted prior to 2016, the applicable performance objective is based upon a multi-year cumulative value creation calculation that considers the Company’s financial performance commencing on the first day of each grant year. The number of performance stock units granted represents the target award and participants have the ability to earn between zero and 150 percent or 200 percent (depending on the grant date) of the target award based upon actual performance. If minimum performance criteria are not achieved, no performance stock units will vest.

Performance stock units granted in 2016 vest based upon a market condition. These performance stock units have a three-year performance objective and a three-year period for vesting (if the applicable performance objective is achieved). The applicable performance objective is based on the Company’s total shareholder return (“TSR”) relative to the Standard & Poors SmallCap 600 Materials Index. The number of performance stock units granted represents the target award and participants have the ability to earn between zero and 200 percent of the target award based upon actual performance. If minimum performance criteria are not achieved, no performance stock units will vest. The Company has the discretion to settle the award in cash rather than shares, although the Company currently expects that all awards will be settled by the issuance of shares.

Compensation expense for non-vested performance stock units with a market condition is recorded over the vesting period based on the fair value at the date of grant. The Company calculated the fair value of the awards on the date of grant using the Monte Carlo valuation model and the assumptions listed below:

	March 2016 Grant
Grant date price per share of performance award	$	18.11
Expected dividend yield per share		0.00	%
Expected volatility		40.86	%
Risk-free interest rate		0.96	%
Look-back period in years		2.84
Grant date fair value per share of performance award	$	23.70

Dividends declared, if any, on the Company’s common stock during the period prior to vesting of the stock units are credited at equivalent value as additional stock units and become payable as additional common shares upon vesting. In the event of termination of employment, other than retirement, death or disability, any non-vested stock units are forfeited, including additional stock units credited from dividends. In the event of termination of employment due to retirement, death or disability, pro-rata vesting of the stock units over the service period will result. There are special vesting provisions for the stock units related to a change in control.

The following table shows a summary of the performance stock units as of September 30, 2016:

Performance Period	Minimum Shares		Target Shares		Maximum Shares
2014 – 2016		0		87,262		130,893
2015 – 2017		0		205,082		410,164
2016 – 2018		0		262,622		525,244

The following table shows a summary of the status and activity of non-vested stock awards for the nine months ended September 30, 2016:

	Restricted Stock Units			Performance Stock Units			Total Stock Units			Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2015		213,208			397,399			610,607		$	27.29
Granted		172,282			264,981			437,263		$	22.02
Credited from dividends		950			1,712			2,662		$	25.47
Vested		(96,950	)		0			(96,950	)	$	28.93
Forfeited		(10,244	)		(106,541	)		(116,785	)	$	37.30
Non-vested at September 30, 2016		279,246			557,551			836,797		$	22.95

Stock Options

Prior to 2015, stock options to most executive officers vest and become exercisable upon the completion of a three-year service period commencing on the grant date. For the 2015 and 2016 grants, the stock options vest in four equal annual installments. The stock options have a term of 10 years. In the event of termination of employment, other than retirement, death or disability, any non-vested options are forfeited. In the event of termination of employment due to retirement, death or disability, pro-rata vesting of the options over the service period will result. There are special vesting provisions for the stock options related to a change in control.

Compensation expense for non-vested stock options is recorded over the vesting period based on the fair value at the date of grant. The Company calculated the fair value of stock options on the date of grant using the Black-Scholes-Merton model and the assumptions listed below:

	March 2016 Grant			March 2015 Grant			February 2014 Grant
Grant date price per share of stock option award	$	18.11		$	17.57		$	37.93
Expected dividend yield per share		0.00	%		3.40	%		2.75	%
Expected life in years		5.96			5.75			6.50
Expected volatility		40.86	%		42.27	%		52.14	%
Risk-free interest rate		1.45	%		1.73	%		1.98	%
Grant date fair value per share of option award	$	7.41		$	5.20		$	15.26

The dividend yield is based on the Company’s current and prospective dividend rate which calculates a continuous dividend yield based upon the market price of the underlying common stock. The Company suspended its dividend in February 2015 and does not expect to declare any dividends for the foreseeable future. The expected life in years for the March 2016 and 2015 grants is based on historical exercise data of options previously granted by the Company. The expected life in years for grants prior to 2015 are based on the simplified method permitted under Securities and Exchange Commission Staff Accounting Bulletin No. 14d.2 which calculates the average of the weighted vesting term and the contractual term of the option. This method was selected due to the lack of historical exercise data with respect to the Company at the time of those grants. Expected volatility is based on the historical volatility of the Company’s common stock and the historical volatility of certain other similar public companies. The risk-free interest rate is based on U.S. Treasury bill rates for the expected life of the option.

The following table shows a summary of the status and activity of stock options for the nine months ended September 30, 2016:

	Options			Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2015		774,249		$	28.46
Granted		211,193		$	18.11
Exercised		(14,301	)	$	26.02
Forfeited		(19,539	)	$	23.70
Outstanding at September 30, 2016		951,602		$	26.29		6.75	$	3.3
Exercisable at September 30, 2016		452,730		$	33.24		4.49	$	1.7

Stock Compensation Expense

Total stock-based compensation expense recognized for the three and nine months ended September 30, 2016 and 2015 is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
(Dollars in millions)
Stock-based compensation expense recognized:
Selling, general and administrative expenses	$	2.3	$	1.1	$	5.7	$	3.1
Less related income tax benefit		1.0		0.4		2.3		1.2
	$	1.3	$	0.7	$	3.4	$	1.9

As of September 30, 2016, total future gross compensation expense related to non-vested stock-based compensation arrangements, which are expected to vest, totaled $12.9 million and the weighted-average period over which this cost is expected to be recognized is approximately 28 months.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Segment Information

9 Months Ended

Sep. 30, 2016

Segment Reporting [Abstract]

Segment Information

9. Segment Information

The Company has three reportable segments: Railroad and Utility Products and Services, Carbon Materials and Chemicals, and Performance Chemicals. The Company’s reportable segments contain multiple aggregated business units since management believes the long-term financial performance of these business units is affected by similar economic conditions. The reportable segments are each managed separately because they manufacture and distribute distinct products with different production processes.

The Company’s Railroad and Utility Products and Services segment sells treated and untreated wood products, manufactured products and services primarily to the railroad and public utility markets. Railroad products and services include procuring and treating items such as crossties, switch ties and various types of lumber used for railroad bridges and crossings and the manufacture of rail joint bars. The segment also operates a railroad services business that conducts engineering, design, repair and inspection services for railroad bridges. Utility products include the treating of transmission and distribution poles and pilings.

The Company’s Carbon Materials and Chemicals segment is primarily a manufacturer of carbon pitch, naphthalene, phthalic anhydride, creosote and carbon black feedstock. Carbon pitch is a critical raw material used in the production of aluminum and for the production of steel in electric arc furnaces. Naphthalene is used for the production of phthalic anhydride and as a surfactant in the production of concrete. Phthalic anhydride is used in the production of plasticizers, polyester resins and alkyd paints. Creosote is used in the treatment of wood and carbon black feedstock is used in the production of carbon black.

The Company’s Performance Chemicals segment develops, manufactures, and markets wood preservation chemicals and wood treatment technologies and services a diverse range of end-markets including infrastructure, residential and commercial construction, and agriculture.

The Company evaluates performance and determines resource allocations based on a number of factors, the primary measure being operating profit or loss from operations. Operating profit does not include equity in earnings of affiliates, other income, interest expense, income taxes or operating costs of Koppers Holdings Inc. The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies. Intersegment transactions are eliminated in consolidation.

The following table sets forth certain sales and operating data, net of all intersegment transactions, for the Company’s segments for the periods indicated:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Revenues from external customers:
Railroad and Utility Products and Services	$	145.7		$	177.6		$	461.5		$	506.6
Carbon Materials and Chemicals		117.8			163.0			337.5			479.6
Performance Chemicals		107.6			93.2			304.0			277.0
Total	$	371.1		$	433.8		$	1,103.0		$	1,263.2
Intersegment revenues:
Carbon Materials and Chemicals	$	26.2		$	23.1		$	68.1		$	63.6
Performance Chemicals		2.3			2.0			6.2			6.3
Total	$	28.5		$	25.1		$	74.3		$	69.9
Depreciation and amortization expense:
Railroad and Utility Products and Services^(a)	$	2.9		$	3.6		$	9.9		$	11.1
Carbon Materials and Chemicals^(b)		6.2			7.2			17.8			19.9
Performance Chemicals		4.7			4.7			14.3			14.2
Total	$	13.8		$	15.5		$	42.0		$	45.2
Operating profit (loss):
Railroad and Utility Products and Services^(c)	$	14.9		$	17.7		$	46.9		$	48.1
Carbon Materials and Chemicals^(d)		(3.9	)		0.0			(29.8	)		(13.8	)
Performance Chemicals		17.6			9.7			52.6			31.6
Corporate^(e)		(0.9	)		(0.4	)		(2.2	)		(4.9	)
Total	$	27.7		$	27.0		$	67.5		$	61.0

(a)	Excludes impairment charges of $2.5 million for the nine months ended September 30, 2015 for a wood treating facility in the United States.

(b)	Excludes impairment charges of $3.5 million for the three and nine months ended September 30, 2016 for a coal tar distillation facility in the United States.

(c)	Includes gain on sale of the Company’s North American utility pole business of $3.2 million and impairment charges of $2.5 million for the nine months ended September 30, 2015.

(d)	Includes gain on sale of the Company’s United Kingdom coal tar distillation business of $2.1 million and impairment charges of $3.5 million for the three and nine months ended September 30, 2016.

(e)	Operating loss for Corporate includes general and administrative costs for Koppers Holdings Inc., the parent company of Koppers Inc., and foreign exchange revaluation related to intercompany loans in connection with a legal reorganization of the Company.

The following table sets forth certain tangible and intangible assets allocated to each of the Company’s segments as of the dates indicated:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Segment assets:
Railroad and Utility Products and Services	$	271.4	$	254.1
Carbon Materials and Chemicals		336.5		368.4
Performance Chemicals		447.3		441.3
All other		45.6		49.1
Total	$	1,100.8	$	1,112.9
Goodwill:
Railroad and Utility Products and Services	$	10.2	$	9.9
Performance Chemicals		177.6		176.7
Total	$	187.8	$	186.6

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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+ Details

Income Taxes

9 Months Ended

Sep. 30, 2016

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

Effective Tax Rate

The income tax provision for interim periods is comprised of an estimated annual effective income tax rate applied to current year ordinary income and tax associated with discrete items. These discrete items generally relate to adjustments to uncertain tax positions and changes of estimated tax to the actual liability determined upon filing tax returns. To determine the annual effective tax rate, management is required to make estimates of annual pretax income in each domestic and foreign jurisdictions in which the Company conducts business. Entities that have historical pre-tax losses and current year estimated pre-tax losses that are not projected to generate a future benefit are excluded from the estimated annual effective income tax rate.

The estimated annual effective income tax rate, excluding the items discussed above, was 29.1 percent and 33.1 percent for the nine months ended September 30, 2016 and 2015, respectively. The estimated annual effective income tax rate differs from the U.S. federal statutory tax rate due to:

	September 30, 2016			September 30, 2015
Federal income tax rate		35.0	%		35.0	%
State income taxes, net of federal tax benefit		1.8			(0.8	)
Foreign earnings taxed at different rates		(9.4	)		(3.7	)
Change in tax contingency reserves		0.6			1.2
Nondeductible expenses		1.2			1.4
Tax credits		(0.4	)		0.0
Other		0.3			0.0
Estimated annual effective income tax rate		29.1	%		33.1	%

Income taxes as a percentage of pretax income were 33.4 percent and 43.7 percent for the nine months ended September 30, 2016 and September 30, 2015, respectively. This exceeds the estimated annual effective income tax rates for these periods primarily because, as explained above, the estimated annual effective income tax rate is applied to pre-tax earnings excluding the losses of our Chinese entities. This effect is partially offset by discrete items.

Discrete items included in income taxes for the nine months ended September 30, 2016 were not material. Discrete items included in income taxes for the nine months ended September 30, 2015 were $1.6 million and were related to recognition of previously unrecognized tax benefits and the closure of an IRS audit of the Company’s US tax returns through 2011.

During the year, management regularly updates estimates of pre-tax income and income tax expense based on changes in the business’ earnings projections, the earnings mix by taxable jurisdiction, uncertain tax positions, and other tax matters. To the extent that actual results vary from these estimates, the actual annual effective income tax rate at the end of the year could be materially different from the estimated annual effective income tax rate as of the end of the third quarter.

Uncertain Tax Positions

The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, individual U.S. state jurisdictions and non-U.S. jurisdictions. With few exceptions, the Company is no longer subject to U.S. federal, state and local, or non-U.S. income tax examinations by tax authorities for years before 2011.

As of September 30, 2016 and December 31, 2015, the total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate, was approximately $5.4 million and $5.2 million, respectively. Unrecognized tax benefits totaled $7.5 million and $7.7 million as of September 30, 2016 and December 31, 2015, respectively. The Company recognizes interest expense and any related penalties from uncertain tax positions in income tax expense. As of September 30, 2016 and December 31, 2015 the Company had accrued approximately $3.4 million and $3.0 million for interest and penalties, respectively.

Inventories

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

Inventories

11. Inventories

Net inventories as of September 30, 2016 and December 31, 2015 are summarized in the table below:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Raw materials	$	154.2	$	169.8
Work in process		15.9		15.5
Finished goods		98.4		97.4
	$	268.5	$	282.7
Less revaluation to LIFO		52.3		56.3
Net	$	216.2	$	226.4

Property, Plant and Equipment

9 Months Ended

Sep. 30, 2016

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

12. Property, Plant and Equipment

Property, plant and equipment as of September 30, 2016 and December 31, 2015 are summarized in the table below:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Land	$	17.4	$	17.6
Buildings		61.9		62.8
Machinery and equipment		712.2		705.6
	$	791.5	$	786.0
Less accumulated depreciation		514.3		508.2
Net	$	277.2	$	277.8

Impairments – Impairment charges were $3.5 million for the three and nine months ended September 30, 2016. Impairment charges were $2.5 million for the nine months ended September 30, 2015. The 2016 charges were related to the Carbon Materials and Chemicals coal tar distillation plant in Clairton, Pennsylvania. The 2015 charges were related to the Railroad and Utility Products and Services wood treating plant in Green Spring, West Virginia and were calculated using a probability-weighted discounted cash flow model.

Pensions and Postretirement Benefit Plans

9 Months Ended

Sep. 30, 2016

Compensation And Retirement Disclosure [Abstract]

Pensions and Postretirement Benefit Plans

13. Pensions and Postretirement Benefit Plans

The Company and its subsidiaries maintain a number of defined benefit and defined contribution plans to provide retirement benefits for employees in the U.S., as well as employees outside the U.S. These plans are maintained and contributions are made in accordance with the Employee Retirement Income Security Act of 1974 (“ERISA”), local statutory law or as determined by the board of directors. The defined benefit pension plans generally provide benefits based upon years of service and compensation. Pension plans are funded except for three domestic non-qualified defined benefit pension plans for certain key executives.

In the U.S., all qualified defined benefit pension plans for salaried and hourly employees have been closed to new participants and have been frozen. Accordingly, these pension plans no longer accrue additional years of service or recognize future increases in compensation for benefit purposes.

The defined contribution plans generally provide retirement assets to employee participants based upon employer and employee contributions to the participant’s individual investment account. The Company also provides retiree medical insurance coverage to certain U.S. employees and a life insurance benefit to most U.S. employees. For salaried employees, the retiree medical and retiree insurance plans have been closed to new participants.

In the third quarter of 2016, the Company offered a cash lump sum or annuity buyout to its terminated deferred vested participants in its U.S. defined benefit pension plan. Approximately 400 participants elected either a lump sum payout or annuity from a third party provider. The total dollar amount to be paid out of our defined benefit plan assets in the fourth quarter of 2016 is estimated to be approximately $14 million. We estimate that the Company will record a pension settlement loss of $4.5 million in the fourth quarter of 2016.

The following table provides the components of net periodic benefit cost for the pension plans and other benefit plans for the three and nine months ended September 30, 2016 and 2015:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Service cost	$	0.4		$	0.5		$	1.3		$	1.5
Interest cost		2.7			2.7			8.3			8.1
Expected return on plan assets		(2.6	)		(3.0	)		(7.9	)		(9.0	)
Amortization of prior service cost		0.0			(0.1	)		0.0			(0.2	)
Amortization of net loss		0.5			1.7			1.7			5.0
Net periodic benefit cost	$	1.0		$	1.8		$	3.4		$	5.4
Defined contribution plan expense^(a)	$	2.0		$	2.1		$	5.8		$	4.2

(a)	The nine months ended September 30, 2015 includes reversal of 2014 discretionary 401k match accrual of $2.2 million.

Debt

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

Debt

14. Debt

Debt at September 30, 2016 and December 31, 2015 was as follows:

	Weighted Average Interest Rate	Maturity	September 30, 2016		December 31, 2015
(Dollars in millions)
Term Loan	4.30%	2019	$	240.0	$	262.5
Revolving Credit Facility	4.30%	2019		110.0		130.0
Construction and other loans	4.76%	2018		43.0		44.8
Senior Notes	7 ⁷/₈%	2019		298.0		297.5
Total debt				691.0		734.8
Less short term debt and current maturities of long-term debt				39.5		39.9
Less unamortized debt issuance costs				9.5		12.5
Long-term debt			$	642.0	$	682.4

Revolving Credit Facility

On August 15, 2014, Koppers Inc. entered into a $500.0 million senior secured revolving credit facility and a $300.0 million senior secured term loan (the “Senior Secured Credit Facilities”). Both borrowings mature on August 15, 2019. The interest rates on these borrowings are variable and are based on LIBOR. The senior secured term loan has quarterly principal repayment obligations of 2.5 percent of the original principal amount borrowed, or $7.5 million.

Borrowings under the revolving credit facility and term loan are secured by a first priority lien on substantially all of the assets of Koppers Inc. and its material domestic subsidiaries. The revolving credit facility and term loan contain certain covenants for Koppers Inc. and its restricted subsidiaries that limit capital expenditures, additional indebtedness, liens, dividends, investments or acquisitions. In addition, such covenants give rise to events of default upon the failure by Koppers Inc. and its restricted subsidiaries to meet certain financial ratios.

The Company entered into an amendment of the revolving credit facility dated April 8, 2016 which reduced the $500.0 million senior secured revolving credit facility to $300.0 million and also amended the leverage ratio covenant requirements. In connection with the amendment, $2.0 million of prior deferred financing costs were required to be written off through interest expense.

As of September 30, 2016, the Company had $148.3 million of unused revolving credit availability for working capital purposes after restrictions from certain letter of credit commitments and other covenants. As of September 30, 2016, $41.7 million of commitments were utilized by outstanding letters of credit.

Construction Loans

On November 18, 2013, the Company’s 75-percent owned subsidiary, Koppers (Jiangsu) Carbon Chemical Company Limited (“KJCC”) entered into two committed loan facility agreements for a combined commitment of RMB 265 million or approximately $44 million. The third party bank provided facility has a commitment amount of RMB 198.8 million and the other committed facility of RMB 66.2 million is provided by the 25-percent non-controlling shareholder in KJCC. Borrowings under the third party bank facility are secured by a letter of credit issued by a bank under the Koppers Inc. revolving credit facility. The committed facilities were used to finance the costs related to the construction of the coal tar distillation plant in Pizhou, Jiangsu province in China.

KJCC will repay the loans in six installments every six months starting in June 2018 with a final repayment on December 21, 2020, the maturity date of the loans.

Senior Notes

The Koppers Inc. 7⁷/₈ percent Senior Notes due 2019 (the “Senior Notes”) were issued on December 1, 2009 at an offering price of 98.311 percent of face value, or $294.9 million and have a principal amount at maturity of $300.0 million. The Senior Notes have an effective interest rate yield of 8¹/₈ percent per annum. The Senior Notes are our senior obligations, are fully and unconditionally guaranteed by Koppers Holdings Inc. and certain of our wholly-owned domestic subsidiaries, and are secured equally and ratably with the obligations under our Senior Secured Credit Facilities.

Interest on the Senior Notes is payable semiannually on December 1 and June 1 each year. On or after December 1, 2015, the Company is entitled to redeem all or a portion of the Senior Notes at a redemption price of 102.625 percent of principal value, declining to a redemption price of 101.313 on or after December 1, 2016 until the redemption price is equivalent to the principal value on December 1, 2017.

The indenture governing the Senior Notes includes customary covenants that restrict, among other things, the ability of Koppers Inc. and its restricted subsidiaries to incur additional debt, pay dividends or make certain other restricted payments, incur liens, merge or sell all or substantially all of the assets of Koppers Inc. or its subsidiaries or enter into various transactions with affiliates.

Asset Retirement Obligations

9 Months Ended

Sep. 30, 2016

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

15. Asset Retirement Obligations

The Company recognizes asset retirement obligations for the removal and disposal of residues; dismantling of certain tanks required by governmental authorities; and cleaning costs for leased and owned rail cars and barges. The following table reflects changes in the carrying values of asset retirement obligations:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Asset retirement obligation at beginning of year	$	46.5		$	30.5
(Divestiture) acquisition		(8.0	)		0.7
Accretion expense		6.2			3.7
Revision in estimated cash flows		0.9			24.4
Cash expenditures		(8.7	)		(12.1	)
Currency translation		(0.7	)		(0.7	)
Balance at end of period	$	36.2		$	46.5

Deferred Revenue

9 Months Ended

Sep. 30, 2016

Deferred Revenue Disclosure [Abstract]

Deferred Revenue

16. Deferred Revenue

The Company defers revenues associated with extended product warranty liabilities based on historical loss experience and sales of extended warranties on certain products. In addition, the Company received an advance payment in 2015 related to an amendment to a 50-year supply agreement with a customer in China. The deferred revenue associated with this amendment is being amortized over the life of the underlying contract. The following table reflects changes in the carrying values of deferred revenue:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Balance at beginning of year	$	30.1		$	2.5
Advance payment		0.0			30.0
Revenue earned		(0.6	)		(1.0	)
Currency translation		(0.8	)		(1.4	)
Balance at end of period	$	28.7		$	30.1

Deferred revenue classified in other long-term liabilities in the consolidated balance sheet totaled $27.6 million as of September 30, 2016 and $29.1 million as of December 31, 2015.

- Definition

The entire disclosure for deferred revenues at the end of the reporting period, and description and amounts of significant changes that occurred during the reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Derivative Financial Instruments

9 Months Ended

Sep. 30, 2016

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

17. Derivative Financial Instruments

The Company utilizes derivative instruments to manage exposures to risks that have been identified and measured and are capable of being controlled. The primary risks managed by the company by using derivative instruments are commodity price risk associated with copper and foreign currency exchange risk associated with a number of currencies, principally the U.S. dollar, the Canadian dollar, the New Zealand dollar, the Euro and British pounds. Swap contracts on copper are used to manage the price risk associated with forecasted purchases of materials used in the Company’s manufacturing processes. Generally, the Company will not hedge cash flow exposures for durations longer than 30 months. The Company enters into foreign currency forward contracts to manage foreign currency risk associated with the Company’s receivable and payable balances. Generally, the Company enters into master netting arrangements with the counterparties and offsets net derivative positions with the same counterparties. Currently, the Company’s agreements do not require cash collateral.

ASC Topic 815-10, “Derivatives and Hedging,” requires companies to recognize all derivative instruments as either assets or liabilities at fair value in the balance sheet. Derivative instruments’ fair value is determined using significant other observable inputs, or Level 2 in the fair value hierarchy. In accordance with ASC Topic 815-10, the Company designates certain commodity swaps as cash flow hedges of forecasted purchases of commodities. For derivative instruments that are designated and qualify as cash flow hedges, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive (loss) income and is reclassified into cost of sales in the same period or periods during which the hedged transaction affects earnings. Gains and losses on the derivative instruments representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized immediately in cost of sales.

For those commodity swaps which are not designated as cash flow hedges, the fair value of the commodity swap is recognized as an asset or liability in the consolidated balance sheet and the related gain or loss on the derivative is reported in current earnings.

As of September 30, 2016 and December 31, 2015, the Company has outstanding copper swap contracts of the following amounts:

	Units Outstanding (in Pounds)		Net Fair Value - Asset (Liability)
	September 30, 2016	December 31, 2015	September 30, 2016			December 31, 2015
(Amounts in millions)
Cash flow hedges	37.8	17.3	$	(0.5	)	$	(9.8	)
Not designated as hedges	3.7	4.0		(0.4	)		(0.7	)
Total	41.5	21.3	$	(0.9	)	$	(10.5	)

As of September 30, 2016 and December 31, 2015, the fair value of the outstanding copper swap contracts is recorded in the balance sheet as follows:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Other current assets	$	1.9		$	0.1
Accrued liabilities		(2.8	)		(10.6	)
Net liability on balance sheet	$	(0.9	)	$	(10.5	)
Accumulated other comprehensive loss, net of tax	$	0.6		$	6.1

Based upon contracts outstanding at September 30, 2016, in the next twelve months the Company estimates that $0.7 million of unrealized losses, net of tax, related to commodity price hedging will be reclassified from other comprehensive income (loss) into earnings.

See Note 6 – Comprehensive Income (Loss) and Equity (Deficit), for amounts recorded in other comprehensive income and for amounts reclassified from accumulated other comprehensive income to net income for the periods specified below. For the three and nine months ended September 30, 2016 and 2015, the following amounts were recognized in earnings related to copper swap contracts:

	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
(Dollars in millions)
(Loss) gain from ineffectiveness of cash flow hedges	$	(0.4	)	$	0.0	$	(0.5	)	$	0.3
(Loss) gain from contracts not designated as hedges		0.0			0.0		(0.3	)		0.1
Net	$	(0.4	)	$	0.0	$	(0.8	)	$	0.4

Forward contracts related to foreign currency are not designated as hedges and fair value changes in these contracts are immediately charged to earnings and are classified in cost of sales in the Condensed Consolidated Statement of Operations and Comprehensive Income (Loss). As of September 30, 2016, the Company has outstanding foreign currency forward contracts with a net fair value totaling $(1.3) million, consisting of a gross derivative liability of $1.5 million (recognized in accrued liabilities in the balance sheet) and a gross derivative asset of $0.2 million (recognized in other current assets in the balance sheet). As of December 31, 2015, the Company has outstanding currency forward contracts with a net fair value totaling $(1.9) million, recognized as a liability in accrued liabilities in the balance sheet.

As of September 30, 2016 and December 31, 2015, the net currency units outstanding were:

	September 30, 2016		December 31, 2015
(In millions)
British Pounds		GBP 4.7		GBP 5.9
New Zealand Dollars		NZD 18.0		NZD 22.5
United States Dollars		USD 46.8		USD 36.0
Canadian Dollars		CAD 1.2		CAD 4.0

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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-Subparagraph (SX 210.4-08.(n))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Commitments and Contingent Liabilities

9 Months Ended

Sep. 30, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingent Liabilities

18. Commitments and Contingent Liabilities

The Company and its subsidiaries are involved in litigation and various proceedings relating to environmental laws and regulations and toxic tort, product liability and other matters. Certain of these matters are discussed below. The ultimate resolution of these contingencies is subject to significant uncertainty and should the Company or its subsidiaries fail to prevail in any of these legal matters or should several of these legal matters be resolved against the Company or its subsidiaries in the same reporting period, these legal matters could, individually or in the aggregate, be material to the consolidated financial statements.

Legal Proceedings

Coal Tar Pitch Cases. Koppers Inc. is one of several defendants in lawsuits filed in two states in which the plaintiffs claim they suffered a variety of illnesses (including cancer) as a result of exposure to coal tar pitch sold by the defendants. There are 103 plaintiffs in 55 cases pending as of September 30, 2016, compared to 110 plaintiffs in 59 cases pending as of December 31, 2015. As of September 30, 2016, there are a total of 54 cases pending in state court in Pennsylvania, and one case pending in state court in Tennessee.

The plaintiffs in all 55 pending cases seek to recover compensatory damages. Plaintiffs in 50 of those cases also seek to recover punitive damages. The plaintiffs in the 54 cases filed in Pennsylvania state court seek unspecified damages in excess of the court’s minimum jurisdictional limit. The plaintiff in the Tennessee state court case seeks damages of $15.0 million. The other defendants in these lawsuits vary from case to case and include companies such as Beazer East, Inc. (“Beazer East”), Honeywell International Inc., Graftech International Holdings, Dow Chemical Company, UCAR Carbon Company, Inc., and SGL Carbon Corporation. Discovery is proceeding in these cases. No trial dates have been set in any of these cases.

The Company has not provided a reserve for these lawsuits because, at this time, the Company cannot reasonably determine the probability of a loss, and the amount of loss, if any, cannot be reasonably estimated. The timing of resolution of these cases cannot be reasonably determined. Although Koppers Inc. is vigorously defending these cases, an unfavorable resolution of these matters may have a material adverse effect on the Company’s business, financial condition, cash flows and results of operations.

Gainesville. Koppers Inc. operated a utility pole treatment plant in Gainesville from December 29, 1988 until its closure in 2009. The property upon which the utility pole treatment plant was located was sold by Koppers Inc. to Beazer East in 2010.

In November 2010, a class action complaint was filed in the Circuit Court of the Eighth Judicial Circuit located in Alachua County, Florida by residential real property owners located in a neighborhood west of and immediately adjacent to the former utility pole treatment plant in Gainesville. The complaint named Koppers Holdings Inc., Koppers Inc., Beazer East and several other parties as defendants. In a second amended complaint, plaintiffs allege that chemicals and contaminants from the Gainesville plant have contaminated real properties of the putative class members, have caused property damage (diminution in value) and have placed residents and owners of the putative class properties at an elevated risk of exposure to and injury from the chemicals at issue. The plaintiffs presently seek a class comprised of all current property owners of single family residential properties within a polygon-shaped area extending approximately two miles from the former plant area (which area encompasses approximately 7,000 owners).

The case was removed to the United States District Court for the Northern District of Florida in December 2010. Koppers Holdings Inc. was dismissed from the case by the district court for lack of personal jurisdiction. Class factual discovery closed in May 2015 and expert witness discovery was completed in August 2015. Discovery on the merits is stayed until further order of the court. Motions were subsequently filed by each side to strike or limit the testimony of the other side’s experts. Plaintiffs filed a motion for class certification on September 30, 2015 and the response of Koppers Inc. was filed on October 30, 2015. A hearing on plaintiffs’ motion for class certification and the parties’ motions relating to experts was held in January 2016 and the parties await a ruling from the court.

The Company has not provided a reserve for this matter because, at this time, it cannot reasonably determine the probability of a loss, and the amount of loss, if any, cannot be reasonably estimated. The timing of resolution of this case cannot be reasonably determined. Although the Company is vigorously defending this case, an unfavorable resolution of this matter may have a material adverse effect on the Company’s business, financial condition, cash flows and results of operations.

Virgin Islands. On August 15, 2016, the court formally dismissed Koppers Performance Chemicals (“PC”) from a putative class action lawsuit filed in the United States District Court of the Virgin Islands which alleged that PC’s wood preservative products and formulas are defective.

Environmental and Other Litigation Matters

The Company and its subsidiaries are subject to federal, state, local and foreign laws and regulations and potential liabilities relating to the protection of the environment and human health and safety including, among other things, the cleanup of contaminated sites, the treatment, storage and disposal of wastes, the discharge of effluent into waterways, the emission of substances into the air and various health and safety matters. The Company’s subsidiaries expect to incur substantial costs for ongoing compliance with such laws and regulations. The Company’s subsidiaries may also face governmental or third-party claims, or otherwise incur costs, relating to cleanup of, or for injuries resulting from, contamination at sites associated with past and present operations. The Company accrues for environmental liabilities when a determination can be made that a liability is probable and reasonably estimable.

Environmental and Other Liabilities Retained or Assumed by Others. The Company’s subsidiaries have agreements with former owners of certain of their operating locations under which the former owners retained, assumed and/or agreed to indemnify such subsidiaries against certain environmental and other liabilities. The most significant of these agreements was entered into at Koppers Inc.’s formation on December 29, 1988 (the “Acquisition”). Under the related asset purchase agreement between Koppers Inc. and Beazer East, subject to certain limitations, Beazer East retained the responsibility for and agreed to indemnify Koppers Inc. against certain liabilities, damages, losses and costs, including, with certain limited exceptions, liabilities under and costs to comply with environmental laws to the extent attributable to acts or omissions occurring prior to the Acquisition and liabilities related to products sold by Beazer East prior to the Acquisition (the “Indemnity”). Beazer Limited, the parent company of Beazer East, unconditionally guaranteed Beazer East’s performance of the Indemnity pursuant to a guarantee (the “Guarantee”). In 1998, the parent company of Beazer East purchased an insurance policy under which the funding and risk of certain environmental and other liabilities relating to the former Koppers Company, Inc. operations of Beazer East (which includes locations purchased from Beazer East by Koppers Inc.) are underwritten by Centre Solutions (a member of the Zurich Group) and Swiss Re. Beazer East is a wholly-owned, indirect subsidiary of Heidelberg Cement AG.

The Indemnity provides different mechanisms, subject to certain limitations, by which Beazer East is obligated to indemnify Koppers Inc. with regard to certain environmental, product and other liabilities and imposes certain conditions on Koppers Inc. before receiving such indemnification, including, in some cases, certain limitations regarding the time period as to which claims for indemnification can be brought. In July 2004, Koppers Inc. and Beazer East agreed to amend the environmental indemnification provisions of the December 29, 1988 asset purchase agreement to extend the indemnification period for pre-closing environmental liabilities through July 2019. As consideration for the amendment, Koppers Inc. paid Beazer East a total of $7.0 million and agreed to share toxic tort litigation defense costs arising from any sites acquired from Beazer East. The July 2004 amendment did not change the provisions of the Indemnity with respect to indemnification for non-environmental claims, such as product liability claims, which may continue to be asserted after July 2019.

Qualified expenditures under the Indemnity are not subject to a monetary limit. Qualified expenditures under the Indemnity include (i) environmental cleanup liabilities required by third parties, such as investigation, remediation and closure costs, relating to pre-December 29, 1988 (“Pre-Closing”) acts or omissions of Beazer East or its predecessors; (ii) environmental claims by third parties for personal injuries, property damages and natural resources damages relating to Pre-Closing acts or omissions of Beazer East or its predecessors; (iii) punitive damages for the acts or omissions of Beazer East and its predecessors without regard to the date of the alleged conduct and (iv) product liability claims for products sold by Beazer East or its predecessors without regard to the date of the alleged conduct. If the third party claims described in sections (i) and (ii) above are not made by July 2019, Beazer East will not be required to pay the costs arising from such claims under the Indemnity. However, with respect to any such claims which are made by July 2019, Beazer East will continue to be responsible for such claims under the Indemnity beyond July 2019. The Indemnity provides for the resolution of issues between Koppers Inc. and Beazer East by an arbitrator on an expedited basis upon the request of either party. The arbitrator could be asked, among other things, to make a determination regarding the allocation of environmental responsibilities between Koppers Inc. and Beazer East. Arbitration decisions under the Indemnity are final and binding on the parties.

Contamination has been identified at most manufacturing and other sites of the Company’s subsidiaries. One site currently owned and operated by Koppers Inc. in the United States is listed on the National Priorities List promulgated under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (“CERCLA”). Currently, at the properties acquired from Beazer East (which includes the National Priorities List site and all but one of the sites permitted under the Resource Conservation and Recovery Act (“RCRA”)), a significant portion of all investigative, cleanup and closure activities are being conducted and paid for by Beazer East pursuant to the terms of the Indemnity. In addition, other of Koppers Inc.’s sites are or have been operated under RCRA and various other environmental permits, and remedial and closure activities are being conducted at some of these sites.

To date, the parties that retained, assumed and/or agreed to indemnify the Company against the liabilities referred to above, including Beazer East, have performed their obligations in all material respects. The Company believes that, for the last three years ended December 31, 2015, amounts paid by Beazer East as a result of its environmental remediation obligations under the Indemnity have averaged in total approximately $10 million per year. Periodically, issues have arisen between Koppers Inc. and Beazer East and/or other indemnitors that have been resolved without arbitration. Koppers Inc. and Beazer East engage in discussions from time to time that involve, among other things, the allocation of environmental costs related to certain operating and closed facilities.

If for any reason (including disputed coverage or financial incapability) one or more of such parties fail to perform their obligations and the Company or its subsidiaries are held liable for or otherwise required to pay all or part of such liabilities without reimbursement, the imposition of such liabilities on the Company or its subsidiaries could have a material adverse effect on its business, financial condition, cash flows and results of operations. Furthermore, the Company could be required to record a contingent liability on its balance sheet with respect to such matters, which could result in a negative impact to the Company’s business, financial condition, cash flows and results of operations.

Domestic Environmental Matters. Koppers Inc. has been named as one of the potentially responsible parties (“PRPs”) at the Portland Harbor CERCLA site located on the Willamette River in Oregon. Koppers Inc. operated a coal tar pitch terminal near the site. Koppers Inc. has responded to an Environmental Protection Agency (“EPA”) information request and has executed a PRP agreement which outlines the process to develop an allocation of past and future costs among more than 80 parties to the site. Koppers Inc. believes it is a de minimus contributor at the site. Additionally, a separate natural resources damages assessment (“NRDA”) is being conducted by a local trustee group. The NRDA is intended to identify further information necessary to estimate liabilities for settlements of natural resource damages (“NRD”) claims. Koppers Inc. may also incur liabilities under the NRD process and has entered into a separate process to develop an allocation of NRDA cost.

The EPA completed its own Feasibility Study (“FS”) and issued a proposed plan for public comment in June 2016. The proposed remedy includes a combination of sediment removal, capping, enhanced and monitored natural remediation and riverbank improvements. The FS does not determine who is responsible for remediation costs. The net present value and undiscounted cost of the proposed remedy as estimated in the proposed plan are approximately $800 million and $1.2 billion, respectively. Responsibility for implementing and funding that work will be decided in the separate allocation process.

In September 2009, Koppers Inc. received a general notice letter notifying it that it may be a PRP at the Newark Bay CERCLA site. In January 2010, Koppers Inc. submitted a response to the general notice letter asserting that Koppers Inc. is a de minimus party at this site.

Other than the estimated costs of participating in the PRP group at the Portland Harbor and Newark Bay CERCLA sites totaling $0.9 million at September 30, 2016 the Company has not provided a reserve for these matters because there has not been a determination of the total cost of the investigations, the remediation that will be required, the amount of natural resources damages or how those costs will be allocated among the PRPs at the sites. Accordingly, the Company believes that it cannot reasonably determine the probability of a loss, and the amount of loss, if any, cannot be reasonably estimated. An unfavorable resolution of these matters may have a material adverse effect on the Company’s business, financial condition, cash flows and results of operations.

In connection with Koppers Inc.’s acquisition of Osmose, Inc., there are two plant sites in the United States where the Company has recorded an environmental remediation liability for soil and groundwater contamination which occurred prior to the acquisition. As of September 30, 2016, the Company’s estimated environmental remediation liability for these acquired sites totals $5.1 million.

Foreign Environmental Matters. In connection with Koppers Inc.’s acquisition of Osmose, Inc., there are three plant sites located in the United Kingdom and Australia where the Company has recorded an environmental remediation liability for soil and groundwater contamination which occurred prior to the acquisition. As of September 30, 2016, the Company’s estimated environmental remediation liability for these acquired sites totals $5.7 million. Osmose Holdings, Inc. has provided an indemnity of up to $5 million for certain environmental response costs incurred prior to August 15, 2017 (the “Osmose Indemnity”). In June 2016, the Company recorded an increase in the receivable under the Osmose Indemnity of $2.9 million related to expected indemnity recoveries associated with the acquired United Kingdom site. As of September 30, 2016, the receivable with respect to the Osmose Indemnity totaled $2.7 million.

In December 2011, the Company ceased manufacturing operations at its Continental Carbon facility located in Kurnell, Australia. The Company has accrued its expected cost of site remediation resulting from the closure of $2.4 million as of September 30, 2016.

Environmental Reserves Rollforward. The following table reflects changes in the accrued liability for environmental matters, of which $8.4 million and $7.0 million are classified as current liabilities at September 30, 2016 and December 31, 2015, respectively:

	Period ended
	September 30, 2016			December 31, 2015
(Dollars in millions)
Balance at beginning of year	$	19.8		$	7.8
Expense		0.4			1.2
Reversal of reserves		(0.1	)		(0.5	)
Cash expenditures		(4.0	)		(1.4	)
Acquisition		0.0			13.7
Disposal		(0.5	)		0.0
Currency translation		(0.4	)		(1.0	)
Balance at end of period	$	15.2		$	19.8

Subsidiary Guarantor Information for Koppers Inc. Senior Notes

9 Months Ended

Sep. 30, 2016

Text Block [Abstract]

Subsidiary Guarantor Information for Koppers Inc. Senior Notes

19. Subsidiary Guarantor Information for Koppers Inc. Senior Notes

On December 1, 2009, Koppers Inc. issued $300.0 million principal value of Senior Notes. Koppers Holdings and each of Koppers Inc.’s 100 percent-owned material domestic subsidiaries other than Koppers Assurance, Inc. fully and unconditionally guarantee the payment of principal and interest on the Senior Notes. The domestic guarantor subsidiaries include Koppers World-Wide Ventures Corporation, Koppers Delaware, Inc., Koppers Concrete Products, Inc., Concrete Partners, Inc., Koppers Asia LLC, Koppers Ventures Inc., Koppers Performance Chemicals Inc., Koppers – Nevada LLC, Koppers NZ, LLC, Koppers Railroad Structures Inc., Wood Protection LP and Wood Protection Management LLC. Non-guarantor subsidiaries are owned directly or indirectly by Koppers Inc.

The guarantee of a guarantor subsidiary will be automatically and unconditionally released and discharged in the event of:

▪

any sale of the capital stock or substantially all of the assets of the guarantor subsidiary;

▪

the designation of the guarantor subsidiary as an unrestricted subsidiary in accordance with the indenture governing the Senior Notes; and

▪

the legal defeasance, covenant defeasance or satisfaction and discharge of the indenture governing the Senior Notes.

Koppers Holdings depends on the dividends from the earnings of Koppers Inc. and its subsidiaries to generate the funds necessary to meet its financial obligations, including the payment of any declared dividend of Koppers Holdings. Koppers Inc.’s credit agreement prohibits it from making dividend payments to Koppers Holdings Inc. unless (1) such dividend payments are permitted by the indenture governing Koppers Inc.’s Senior Notes and (2) no event of default or potential default has occurred or is continuing under the credit agreement. The indenture governing Koppers Inc.’s Senior Notes restricts its ability to finance Koppers Holdings Inc.’s payment of dividends if (1) a default has occurred or would result from such financing, (2) a restricted subsidiary of Koppers Inc. which is not a guarantor under the indenture is not able to incur additional indebtedness (as defined in the indenture), and (3) the sum of all restricted payments (as defined in the indenture) have exceeded the permitted amount (referred to as the “basket”) at such point in time.

The Koppers Inc. Senior Secured Credit Facilities, as amended, provide for a revolving credit facility of up to $300.0 million and a term loan of $247.5 million at variable rates. Borrowings under the revolving credit facility are secured by a first priority lien on substantially all of the assets of Koppers Inc. and its material domestic subsidiaries. The revolving credit facility contains certain covenants for Koppers Inc. and its restricted subsidiaries that limit capital expenditures, additional indebtedness, liens, dividends and investments or acquisitions. In addition, such covenants give rise to events of default upon the failure by Koppers Inc. and its restricted subsidiaries to meet certain financial ratios.

As of September 30, 2016, Koppers Inc. net assets are $20.0 million, which are not restricted for distribution to Koppers Holdings Inc. Cash dividends paid to Koppers Holdings Inc. by its subsidiaries totaled $1.1 million and $6.2 million for the nine months ended September 30, 2016 and 2015, respectively.

Condensed Consolidating Statement of Operations

For the Three Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	165.7		$	104.7	$	128.9		$	(28.2	)	$	371.1
Cost of sales including depreciation and amortization		0.0			164.0			73.5		103.6			(28.2	)		312.9
Gain on sale of business		0.0			0.0			0.0		(2.1	)		0.0			(2.1	)
Selling, general and administrative		0.5			10.6			13.7		7.8			0.0			32.6
Operating profit (loss)		(0.5	)		(8.9	)		17.5		19.6			0.0			27.7
Other income (loss)		0.0			0.1			0.8		(0.3	)		(0.4	)		0.2
Equity income (loss) of subsidiaries		12.6			33.7			15.2		0.0			(61.5	)		0.0
Interest expense		0.0			11.0			0.0		1.1			(0.4	)		11.7
Income taxes		0.0			1.9			0.0		2.3			0.0			4.2
Income (loss) from continuing operations		12.1			12.0			33.5		15.9			(61.5	)		12.0
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(0.2	)		0.0			(0.2	)
Net income (loss) attributable to Koppers		12.1			12.0			33.5		16.0			(61.5	)		12.1
Comprehensive income (loss) attributable to Koppers		14.3			14.9			35.4		15.6			(65.9	)		14.3

Condensed Consolidating Statement of Operations

For the Three Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	216.7		$	88.7	$	157.9		$	(29.5	)	$	433.8
Cost of sales including depreciation and amortization		0.0			197.6			68.4		139.9			(29.9	)		376.0
Selling, general and administrative		0.4			9.6			10.3		10.5			0.0			30.8
Operating profit (loss)		(0.4	)		9.5			10.0		7.5			0.4			27.0
Other income (loss)		0.0			(2.6	)		1.3		1.8			(0.5	)		0.0
Equity income (loss) of subsidiaries		10.6			16.8			4.8		0.0			(32.2	)		0.0
Interest expense		0.0			11.5			0.0		1.6			(0.5	)		12.6
Income taxes		0.1			1.6			0.3		3.2			0.0			5.2
Income (loss) from continuing operations		10.1			10.6			15.8		4.5			(31.8	)		9.2
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(1.0	)		0.0			(1.0	)
Net income (loss) attributable to Koppers	$	10.1		$	10.6		$	15.8	$	5.4		$	(31.8	)	$	10.1
Comprehensive income (loss) attributable to Koppers	$	(3.5	)	$	(3.0	)	$	1.2	$	(7.9	)	$	9.7		$	(3.5	)

Condensed Consolidating Statement of Operations

For the Nine Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	515.2		$	272.0	$	391.6		$	(75.8	)	$	1,103.0
Cost of sales including depreciation and amortization		0.0			499.8			195.4		326.4			(77.1	)		944.5
Gain on sale of business		0.0			0.0			0.0		(2.1	)		0.0			(2.1	)
Selling, general and administrative		1.3			31.5			27.9		32.4			0.0			93.1
Operating (loss) profit		(1.3	)		(16.1	)		48.7		34.9			1.3			67.5
Other income (loss)		0.0			0.2			3.5		(0.2	)		(1.3	)		2.2
Equity income of subsidiaries		24.2			77.2			23.3		0.0			(124.7	)		0.0
Interest expense		0.0			36.1			0.0		3.5			(1.3	)		38.3
Income taxes		0.0			1.3			0.4		8.8			0.0			10.5
Income from continuing operations		22.9			23.9			75.1		22.4			(123.4	)		20.9
Discontinued operations		0.0			0.0			0.0		0.5			0.0			0.5
Noncontrolling interests		0.0			0.0			0.0		(1.5	)		0.0			(1.5	)
Net income attributable to Koppers	$	22.9		$	23.9		$	75.1	$	24.4		$	(123.4	)	$	22.9
Comprehensive income (loss) attributable to Koppers	$	33.1		$	34.4		$	84.7	$	27.8		$	(146.9	)	$	33.1

Condensed Consolidating Statement of Operations

For the Nine Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	613.7		$	260.4	$	467.1		$	(78.0	)	$	1,263.2
Cost of sales including depreciation and amortization		0.0			583.2			200.0		405.0			(76.5	)		1,111.7
Gain on sale of business		0.0			(3.2	)		0.0		0.0			0.0			(3.2	)
Selling, general and administrative		1.5			31.8			28.9		31.5			0.0			93.7
Operating (loss) profit		(1.5	)		1.9			31.5		30.6			(1.5	)		61.0
Other income (loss)		0.0			0.5			3.3		(1.8	)		(1.6	)		0.4
Equity income (loss) of subsidiaries		16.7			48.7			14.5		0.0			(79.9	)		0.0
Interest expense		0.0			34.6			0.0		5.5			(1.6	)		38.5
Income taxes		(0.5	)		(0.2	)		0.6		10.1			0.0			10.0
Income (loss) from continuing operations		15.7			16.7			48.7		13.2			(81.4	)		12.9
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(2.9	)		0.0			(2.9	)
Net income (loss) attributable to Koppers	$	15.7		$	16.7		$	48.7	$	16.0		$	(81.4	)	$	15.7
Comprehensive income (loss) attributable to Koppers	$	(4.8	)	$	(3.8	)	$	25.8	$	(3.3	)	$	(18.7	)	$	(4.8	)

Condensed Consolidating Balance Sheet

September 30, 2016

	Parent		Koppers Inc.		Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
ASSETS
Cash and cash equivalents	$	0.0	$	0.0	$	0.0		$	17.7		$	0.0		$	17.7
Receivables, net		0.0		59.2		34.2			78.0			0.0			171.4
Affiliated receivables		0.0		8.8		9.1			13.1			(31.0	)		0.0
Inventories, net		0.0		101.4		24.1			91.6			(0.9	)		216.2
Loan to related party		0.0		0.0		0.0			9.2			0.3			9.5
Other current assets		0.0		5.9		3.4			20.9			0.0			30.2
Total current assets		0.0		175.3		70.8			230.5			(31.6	)		445.0
Equity investments		20.3		770.8		192.7			(0.1	)		(983.7	)		0.0
Property, plant and equipment, net		0.0		119.4		39.0			118.8			0.0			277.2
Goodwill		0.0		0.8		153.1			33.9			0.0			187.8
Intangible assets, net		0.0		8.0		109.7			28.8			0.0			146.5
Deferred tax assets		0.0		29.8		(2.3	)		6.2			0.0			33.7
Affiliated loan receivables		0.0		41.8		270.6			32.7			(345.1	)		0.0
Other assets		0.0		5.8		4.5			0.3			0.0			10.6
Total assets		20.3		1,151.7		838.1			451.1			(1,360.4	)		1,100.8
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable		0.0		62.5		38.5			40.9			0.0			141.9
Affiliated payables		0.0		20.8		1.5			17.2			(39.5	)		0.0
Accrued liabilities		0.0		42.9		19.7			39.8			0.0			102.4
Current maturities of long-term debt		0.0		30.2		0.0			9.3			0.0			39.5
Total current liabilities		0.0		156.4		59.7			107.2			(39.5	)		283.8
Long-term debt		0.0		608.5		0.0			33.5			0.0			642.0
Affiliated debt		0.0		283.5		22.3			39.3			(345.1	)		0.0
Other long-term liabilities		0.0		83.3		14.1			53.0			(0.1	)		150.3
Total liabilities		0.0		1,131.7		96.1			233.0			(384.7	)		1,076.1
Koppers shareholders’ equity (deficit)		20.3		20.0		742.0			213.7			(975.7	)		20.3
Noncontrolling interests		0.0		0.0		0.0			4.4			0.0			4.4
Total liabilities and equity (deficit)	$	20.3	$	1,151.7	$	838.1		$	451.1		$	(1,360.4	)	$	1,100.8

Condensed Consolidating Balance Sheet

December 31, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Consolidating Adjustments			Consolidated
(Dollars in millions)
ASSETS
Cash and cash equivalents	$	0.0		$	0.1		$	0.7	$	21.0	$	0.0		$	21.8
Receivables, net		0.0			60.4			23.7		75.5		0.0			159.6
Affiliated receivables		0.0			14.3			15.2		4.4		(33.9	)		0.0
Inventories, net		0.0			111.9			24.9		91.8		(2.2	)		226.4
Other current assets		0.0			3.7			1.9		30.9		0.0			36.5
Total current assets		0.0			190.4			66.4		223.6		(36.1	)		444.3
Equity investments		(19.0	)		703.2			165.7		0.0		(849.9	)		0.0
Property, plant and equipment, net		0.0			117.5			41.2		119.1		0.0			277.8
Goodwill		0.0			0.8			153.1		32.7		0.0			186.6
Intangible assets, net		0.0			8.7			117.6		29.8		0.0			156.1
Deferred tax assets		0.0			29.8			0.8		5.7		0.3			36.6
Affiliated loan receivables		0.7			29.6			222.6		31.7		(284.6	)		0.0
Other assets		(0.2	)		4.5			4.9		2.3		0.0			11.5
Total assets	$	(18.5	)	$	1,084.5		$	772.3	$	444.9	$	(1,170.3	)	$	1,112.9
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	$	0.0		$	73.8		$	18.9	$	48.1	$	0.0		$	140.8
Affiliated payables		0.0			16.6			10.9		15.3		(42.8	)		0.0
Accrued liabilities		0.0			35.6			23.4		40.8		0.0			99.8
Current maturities of long-term debt		0.0			30.2			0.0		9.7		0.0			39.9
Total current liabilities		0.0			156.2			53.2		113.9		(42.8	)		280.5
Long-term debt		0.0			647.5			0.0		34.9		0.0			682.4
Affiliated debt		0.0			217.5			29.5		36.9		(283.9	)		0.0
Other long-term liabilities		0.0			81.6			13.2		67.6		0.0			162.4
Total liabilities		0.0			1,102.8			95.9		253.3		(326.7	)		1,125.3
Koppers shareholders’ equity (deficit)		(18.5	)		(18.3	)		676.4		185.5		(843.6	)		(18.5	)
Noncontrolling interests		0.0			0.0			0.0		6.1		0.0			6.1
Total liabilities and equity (deficit)	$	(18.5	)	$	1,084.5		$	772.3	$	444.9	$	(1,170.3	)	$	1,112.9

Condensed Consolidating Statement of Cash Flows

For the Nine Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Cash provided by (used in) operating activities	$	(0.2	)	$	10.8		$	76.1		$	15.7		$	(19.9	)	$	82.5
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions		0.0			(20.0	)		(3.2	)		(9.0	)		0.0			(32.2	)
Repayments (loans to) from affiliates		0.0			(12.2	)		(48.0	)		(1.0	)		61.2			0.0
Net cash (used in) provided by divestitures and asset sales		0.0			0.0			0.7			(5.2	)		0.0			(4.5	)
Net cash provided by (used in) investing activities		0.0			(32.2	)		(50.5	)		(15.2	)		61.2			(36.7	)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt		0.0			(42.5	)		0.0			(0.9	)		0.0			(43.4	)
Borrowings (repayments) of affiliated debt		0.0			66.0			(7.2	)		2.4			(61.2	)		0.0
Deferred financing costs		0.0			(1.4	)		0.0			0.0			0.0			(1.4	)
Dividends paid		0.0			(0.8	)		(19.1	)		0.0			19.9			0.0
Stock repurchased		0.2			0.0			0.0			0.0			0.0			0.2
Net cash provided by (used in) financing activities		0.2			21.3			(26.3	)		1.5			(41.3	)		(44.6	)
Effect of exchange rates on cash		0.0			0.0			0.0			(5.3	)		0.0			(5.3	)
Net increase (decrease) in cash and cash equivalents		0.0			(0.1	)		(0.7	)		(3.3	)		0.0			(4.1	)
Cash and cash equivalents at beginning of year		0.0			0.1			0.7			21.0			0.0			21.8
Cash and cash equivalents at end of period	$	0.0		$	0.0		$	0.0		$	17.7		$	0.0		$	17.7

Condensed Consolidating Statement of Cash Flows

For the Nine Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Cash provided by (used in) operating activities	$	5.4		$	10.7		$	58.2		$	29.9		$	(9.1	)	$	95.1
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions		0.0			(32.5	)		(4.1	)		(5.1	)		0.0			(41.7	)
Repayments (loans to) from affiliates		0.0			3.8			(49.9	)		(1.4	)		47.5			0.0
Net cash proceeds from divestitures and asset sales		0.0			12.4			2.2			0.1			0.0			14.7
Net cash provided by (used in) investing activities		0.0			(16.3	)		(51.8	)		(6.4	)		47.5			(27.0	)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt		0.0			(87.8	)		0.1			1.4			0.0			(86.3	)
Borrowings (repayments) of affiliated debt		0.0			100.6			(3.9	)		(49.2	)		(47.5	)		0.0
Deferred financing costs		0.0			(1.0	)		0.0			0.0			0.0			(1.0	)
Dividends paid		(5.1	)		(6.2	)		(3.1	)		(3.4	)		9.1			(8.7	)
Stock repurchased		(0.3	)		0.0			0.0			0.0			0.0			(0.3	)
Net cash provided by (used in) financing activities		(5.4	)		5.6			(6.9	)		(51.2	)		(38.4	)		(96.3	)
Effect of exchange rates on cash		0.0			0.1			0.0			10.0			0.0			10.1
Net increase (decrease) in cash and cash equivalents		0.0			0.1			(0.5	)		(17.7	)		0.0			(18.1	)
Cash and cash equivalents at beginning of year		0.0			0.0			0.9			50.2			0.0			51.1
Cash and cash equivalents at end of period	$	0.0		$	0.1		$	0.4		$	32.5		$	0.0		$	33.0

New Accounting Pronouncements (Policies)	9 Months Ended
New Accounting Pronouncements (Policies)	Sep. 30, 2016
Accounting Changes And Error Corrections [Abstract]
New Accounting Pronouncements	In August 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” The update amends the guidance in Accounting Standards Codification 230, Statement of Cash Flows, and clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows with the objective of reducing the existing diversity in practice related to eight specific cash flow issues. The amendments in this update are effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company is in the process of assessing the impact the adoption of this ASU will have on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09, “Improvements to Employee Share-Based Payment Accounting.” This ASU makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The amendments in this ASU are effective for annual periods beginning after December 15, 2016 and for the interim periods therein. The Company does not expect the adoption of this ASU will have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-08, “Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” that amends the principal versus agent guidance in ASU 2014-09. ASU 2016-08 clarifies that the analysis must focus on whether the entity has control of the goods or services before they are transferred to the customer. ASU 2016-08 also provides additional guidance about how to apply the control principle when services are provided and when goods or services are combined with other goods or services. The effective date of the standard for the Company will coincide with the effective date of ASU 2014-09 on January 1, 2018. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” ASU 2016-02 requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than one year. Recognition, measurement and presentation of expenses will depend on classification as a finance or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The standard is effective January 1, 2019 and early adoption is permitted. The guidance requires a modified retrospective adoption. The Company is currently evaluating the impact of the adoption of ASU 2016-02 will have on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs,” which requires companies to present debt issuance costs associated with a debt liability as a deduction from the carrying amount of that debt liability on the balance sheet rather than being capitalized as an asset. The standard is effective for interim and annual periods beginning after December 15, 2015, and retrospective presentation is required. The Company adopted this guidance as of January 1, 2016, which resulted in $9.5 million and $12.5 million of debt issuance costs being reclassified from other assets to long-term debt as of September 30, 2016 and December 31, 2015, respectively. In February 2015, the FASB issued ASU No. 2015-02, “Consolidation (Topic 810): Amendments to the Consolidation Analysis,” which provides consolidation guidance that entities must use to evaluate specific ownership and contractual arrangements that lead to a consolidation conclusion. The updates could change consolidation outcomes affecting presentation and disclosures. The Company adopted this guidance as of January 1, 2016, which did not have a material effect on the Company’s financial statements. In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 requires an entity to recognize revenue in a manner that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. An entity can either adopt this amendment retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the update recognized at the date of initial application. This guidance will be effective January 1, 2018. The Company is currently evaluating the impact of the adoption of ASU 2014-09 on the Company’s financial statements.

Plant Closures and Divestitures (Tables)

9 Months Ended

Sep. 30, 2016

Discontinued Operations And Disposal Groups [Abstract]

Summary of Restructuring Activities and Related Reserves

Details of the restructuring activities and related reserves are as follows:

	Severance and employee benefits			Environmental remediation			Site demolition			Other			Total
(Dollars in millions)
Reserve at December 31, 2014	$	0.0		$	4.1		$	3.9		$	0.1		$	8.1
Accrual		2.2			0.6			13.7			1.3			17.8
Cost charged against assets		0.0			0.0			0.0			(1.3	)		(1.3	)
Reversal of accrued charges		0.0			0.0			(0.3	)		0.0			(0.3	)
Cash paid		(0.2	)		0.0			(4.8	)		(0.1	)		(5.1	)
Currency translation		0.0			(0.4	)		(0.3	)		0.0			(0.7	)
Reserve at December 31, 2015	$	2.0		$	4.3		$	12.2		$	0.0		$	18.5
Accrual		2.1			0.0			4.8			4.4			11.3
Cost charged against assets		0.0			0.0			0.0			(0.7	)		(0.7	)
Reversal of accrued charges		(1.8	)		(0.5	)		(8.4	)		(0.1	)		(10.8	)
Cash paid		(1.1	)		(1.5	)		(5.8	)		0.0			(8.4	)
Currency translation		(0.1	)		0.1			(0.7	)		0.0			(0.7	)
Reserve at September 30, 2016	$	1.1		$	2.4		$	2.1		$	3.6		$	9.2

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Schedule of Company's Financial Instruments

Carrying amounts and the related estimated fair values of the Company’s financial instruments as of September 30, 2016 and December 31, 2015 are as follows:

	September 30, 2016				December 31, 2015
	Fair Value		Carrying Value		Fair Value		Carrying Value
(Dollars in millions)
Financial assets:
Cash and cash equivalents, including restricted cash	$	17.7	$	17.7	$	21.8	$	21.8
Investments and other assets^(a)		1.1		1.1		1.1		1.1
Financial liabilities:
Long-term debt (including current portion)	$	691.0	$	681.5	$	724.6	$	722.3

(a)	Excludes equity method investments.

Comprehensive Income (Loss) and Equity (Deficit) (Tables)

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Schedule of Comprehensive Income (Loss)

Total comprehensive income (loss) for the three and nine months ended September 30, 2016 and 2015 is summarized in the table below:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Net income	$	11.9		$	9.1		$	21.4		$	12.8
Other comprehensive income (loss):
Change in currency translation adjustment		0.7			(13.6	)		4.1			(21.9	)
Change in unrealized gains (losses) on cash flow hedges, net of tax (expense) benefit of $(1.0), $0.5, $(3.4) and $0.8		1.7			(1.2	)		5.5			(1.7	)
Change in unrecognized pension net income, net of tax (expense) benefit of $(0.1), $(0.7), $(0.4) and $(2.0)		(0.2	)		1.0			0.4			3.0
Change in unrecognized prior service cost		0.0			0.0			0.0			(0.1	)
Total comprehensive income (loss)		14.1			(4.7	)		31.4			(7.9	)
Less: Comprehensive loss attributable to noncontrolling interests		(0.2	)		(1.2	)		(1.7	)		(3.1	)
Comprehensive income (loss) attributable to Koppers	$	14.3		$	(3.5	)	$	33.1		$	(4.8	)

Schedule of Change in Equity (Deficit)

The following tables present the change in equity (deficit) for the nine months ended September 30, 2016 and 2015, respectively:

(Dollars in millions)	Total Koppers Shareholders’ Equity (Deficit)			Noncontrolling Interests			Total Equity (Deficit)
Balance at December 31, 2015	$	(18.5	)	$	6.1		$	(12.4	)
Net income (loss)		22.9			(1.5	)		21.4
Employee stock plans		6.0			0.0			6.0
Other comprehensive income		10.2			(0.2	)		10.0
Repurchases of common stock		(0.3	)		0.0			(0.3	)
Balance at September 30, 2016	$	20.3		$	4.4		$	24.7

(Dollars in millions)	Total Koppers Shareholders’ Equity			Noncontrolling Interests			Total Equity
Balance at December 31, 2014	$	70.0		$	13.9		$	83.9
Net income (loss)		15.7			(2.9	)		12.8
Employee stock plans		3.1			0.0			3.1
Other comprehensive loss		(20.5	)		(0.2	)		(20.7	)
Dividends		0.0			(3.5	)		(3.5	)
Repurchases of common stock		(0.3	)		0.0			(0.3	)
Balance at September 30, 2015	$	68.0		$	7.3		$	75.3

Earnings per Common Share (Tables)

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Earnings per Common Share

The following table sets forth the computation of basic and diluted earnings per common share:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016		2015
(Dollars in millions, except share amounts, in thousands, and per share amounts)
Net income attributable to Koppers	$	12.1		$	10.1		$	22.9	$	15.7
Less: (Loss) income from discontinued operations		(0.1	)		(0.1	)		0.5		(0.1	)
Income from continuing operations attributable to Koppers	$	12.2		$	10.2		$	22.4	$	15.8
Weighted average common shares outstanding:
Basic		20,657			20,553			20,627		20,537
Effect of dilutive securities		506			79			348		72
Diluted		21,163			20,632			20,975		20,609
Income per common share – continuing operations:
Basic income per common share	$	0.59		$	0.49		$	1.08	$	0.77
Diluted income per common share		0.58			0.49			1.07		0.76
Other data:
Antidilutive securities excluded from computation of diluted earnings per common share		339			738			421		671

Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2016

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

The Company calculated the fair value of stock options on the date of grant using the Black-Scholes-Merton model and the assumptions listed below:

	March 2016 Grant			March 2015 Grant			February 2014 Grant
Grant date price per share of stock option award	$	18.11		$	17.57		$	37.93
Expected dividend yield per share		0.00	%		3.40	%		2.75	%
Expected life in years		5.96			5.75			6.50
Expected volatility		40.86	%		42.27	%		52.14	%
Risk-free interest rate		1.45	%		1.73	%		1.98	%
Grant date fair value per share of option award	$	7.41		$	5.20		$	15.26

Summary of Performance Stock Units

The following table shows a summary of the performance stock units as of September 30, 2016:

Performance Period	Minimum Shares		Target Shares		Maximum Shares
2014 – 2016		0		87,262		130,893
2015 – 2017		0		205,082		410,164
2016 – 2018		0		262,622		525,244

Summary of Status and Activity of Non-Vested Stock Awards

The following table shows a summary of the status and activity of non-vested stock awards for the nine months ended September 30, 2016:

	Restricted Stock Units			Performance Stock Units			Total Stock Units			Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2015		213,208			397,399			610,607		$	27.29
Granted		172,282			264,981			437,263		$	22.02
Credited from dividends		950			1,712			2,662		$	25.47
Vested		(96,950	)		0			(96,950	)	$	28.93
Forfeited		(10,244	)		(106,541	)		(116,785	)	$	37.30
Non-vested at September 30, 2016		279,246			557,551			836,797		$	22.95

Summary of Status and Activity of Stock Options

The following table shows a summary of the status and activity of stock options for the nine months ended September 30, 2016:

	Options			Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2015		774,249		$	28.46
Granted		211,193		$	18.11
Exercised		(14,301	)	$	26.02
Forfeited		(19,539	)	$	23.70
Outstanding at September 30, 2016		951,602		$	26.29		6.75	$	3.3
Exercisable at September 30, 2016		452,730		$	33.24		4.49	$	1.7

Schedule of Stock-based Compensation Expense Recognized and Cash Received from Exercise of Stock Options

Stock Compensation Expense

Total stock-based compensation expense recognized for the three and nine months ended September 30, 2016 and 2015 is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
(Dollars in millions)
Stock-based compensation expense recognized:
Selling, general and administrative expenses	$	2.3	$	1.1	$	5.7	$	3.1
Less related income tax benefit		1.0		0.4		2.3		1.2
	$	1.3	$	0.7	$	3.4	$	1.9

Performance Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

The Company calculated the fair value of the awards on the date of grant using the Monte Carlo valuation model and the assumptions listed below:

	March 2016 Grant
Grant date price per share of performance award	$	18.11
Expected dividend yield per share		0.00	%
Expected volatility		40.86	%
Risk-free interest rate		0.96	%
Look-back period in years		2.84
Grant date fair value per share of performance award	$	23.70

Segment Information (Tables)

9 Months Ended

Sep. 30, 2016

Segment Reporting [Abstract]

Summary of Results of Segment Operations

The following table sets forth certain sales and operating data, net of all intersegment transactions, for the Company’s segments for the periods indicated:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Revenues from external customers:
Railroad and Utility Products and Services	$	145.7		$	177.6		$	461.5		$	506.6
Carbon Materials and Chemicals		117.8			163.0			337.5			479.6
Performance Chemicals		107.6			93.2			304.0			277.0
Total	$	371.1		$	433.8		$	1,103.0		$	1,263.2
Intersegment revenues:
Carbon Materials and Chemicals	$	26.2		$	23.1		$	68.1		$	63.6
Performance Chemicals		2.3			2.0			6.2			6.3
Total	$	28.5		$	25.1		$	74.3		$	69.9
Depreciation and amortization expense:
Railroad and Utility Products and Services^(a)	$	2.9		$	3.6		$	9.9		$	11.1
Carbon Materials and Chemicals^(b)		6.2			7.2			17.8			19.9
Performance Chemicals		4.7			4.7			14.3			14.2
Total	$	13.8		$	15.5		$	42.0		$	45.2
Operating profit (loss):
Railroad and Utility Products and Services^(c)	$	14.9		$	17.7		$	46.9		$	48.1
Carbon Materials and Chemicals^(d)		(3.9	)		0.0			(29.8	)		(13.8	)
Performance Chemicals		17.6			9.7			52.6			31.6
Corporate^(e)		(0.9	)		(0.4	)		(2.2	)		(4.9	)
Total	$	27.7		$	27.0		$	67.5		$	61.0

(a)	Excludes impairment charges of $2.5 million for the nine months ended September 30, 2015 for a wood treating facility in the United States.

(b)	Excludes impairment charges of $3.5 million for the three and nine months ended September 30, 2016 for a coal tar distillation facility in the United States.

(c)	Includes gain on sale of the Company’s North American utility pole business of $3.2 million and impairment charges of $2.5 million for the nine months ended September 30, 2015.

(d)	Includes gain on sale of the Company’s United Kingdom coal tar distillation business of $2.1 million and impairment charges of $3.5 million for the three and nine months ended September 30, 2016.

(e)	Operating loss for Corporate includes general and administrative costs for Koppers Holdings Inc., the parent company of Koppers Inc., and foreign exchange revaluation related to intercompany loans in connection with a legal reorganization of the Company.

Summary of Tangible and Intangible Assets by Segments

The following table sets forth certain tangible and intangible assets allocated to each of the Company’s segments as of the dates indicated:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Segment assets:
Railroad and Utility Products and Services	$	271.4	$	254.1
Carbon Materials and Chemicals		336.5		368.4
Performance Chemicals		447.3		441.3
All other		45.6		49.1
Total	$	1,100.8	$	1,112.9
Goodwill:
Railroad and Utility Products and Services	$	10.2	$	9.9
Performance Chemicals		177.6		176.7
Total	$	187.8	$	186.6

Income Taxes (Tables)

9 Months Ended

Sep. 30, 2016

Income Tax Disclosure [Abstract]

Summary of Income Taxes Reconciled with Federal Statutory Rate

The estimated annual effective income tax rate differs from the U.S. federal statutory tax rate due to:

	September 30, 2016			September 30, 2015
Federal income tax rate		35.0	%		35.0	%
State income taxes, net of federal tax benefit		1.8			(0.8	)
Foreign earnings taxed at different rates		(9.4	)		(3.7	)
Change in tax contingency reserves		0.6			1.2
Nondeductible expenses		1.2			1.4
Tax credits		(0.4	)		0.0
Other		0.3			0.0
Estimated annual effective income tax rate		29.1	%		33.1	%

Inventories (Tables)

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

Components of Inventories

Net inventories as of September 30, 2016 and December 31, 2015 are summarized in the table below:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Raw materials	$	154.2	$	169.8
Work in process		15.9		15.5
Finished goods		98.4		97.4
	$	268.5	$	282.7
Less revaluation to LIFO		52.3		56.3
Net	$	216.2	$	226.4

Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2016

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

Property, plant and equipment as of September 30, 2016 and December 31, 2015 are summarized in the table below:

	September 30, 2016		December 31, 2015
(Dollars in millions)
Land	$	17.4	$	17.6
Buildings		61.9		62.8
Machinery and equipment		712.2		705.6
	$	791.5	$	786.0
Less accumulated depreciation		514.3		508.2
Net	$	277.2	$	277.8

Pensions and Postretirement Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2016

Compensation And Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Cost for Pension Plans and Other Benefit Plans

The following table provides the components of net periodic benefit cost for the pension plans and other benefit plans for the three and nine months ended September 30, 2016 and 2015:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(Dollars in millions)
Service cost	$	0.4		$	0.5		$	1.3		$	1.5
Interest cost		2.7			2.7			8.3			8.1
Expected return on plan assets		(2.6	)		(3.0	)		(7.9	)		(9.0	)
Amortization of prior service cost		0.0			(0.1	)		0.0			(0.2	)
Amortization of net loss		0.5			1.7			1.7			5.0
Net periodic benefit cost	$	1.0		$	1.8		$	3.4		$	5.4
Defined contribution plan expense^(a)	$	2.0		$	2.1		$	5.8		$	4.2

(a)	The nine months ended September 30, 2015 includes reversal of 2014 discretionary 401k match accrual of $2.2 million.

Debt (Tables)

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

Schedule of Long-Term Debt Instruments

Debt at September 30, 2016 and December 31, 2015 was as follows:

	Weighted Average Interest Rate	Maturity	September 30, 2016		December 31, 2015
(Dollars in millions)
Term Loan	4.30%	2019	$	240.0	$	262.5
Revolving Credit Facility	4.30%	2019		110.0		130.0
Construction and other loans	4.76%	2018		43.0		44.8
Senior Notes	7 ⁷/₈%	2019		298.0		297.5
Total debt				691.0		734.8
Less short term debt and current maturities of long-term debt				39.5		39.9
Less unamortized debt issuance costs				9.5		12.5
Long-term debt			$	642.0	$	682.4

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

+ Details

Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2016

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Carrying Values of Asset Retirement Obligations

The following table reflects changes in the carrying values of asset retirement obligations:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Asset retirement obligation at beginning of year	$	46.5		$	30.5
(Divestiture) acquisition		(8.0	)		0.7
Accretion expense		6.2			3.7
Revision in estimated cash flows		0.9			24.4
Cash expenditures		(8.7	)		(12.1	)
Currency translation		(0.7	)		(0.7	)
Balance at end of period	$	36.2		$	46.5

Deferred Revenue (Tables)

9 Months Ended

Sep. 30, 2016

Deferred Revenue Disclosure [Abstract]

Deferred Revenue from Extended Product Warranty Liabilities

The following table reflects changes in the carrying values of deferred revenue:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Balance at beginning of year	$	30.1		$	2.5
Advance payment		0.0			30.0
Revenue earned		(0.6	)		(1.0	)
Currency translation		(0.8	)		(1.4	)
Balance at end of period	$	28.7		$	30.1

Derivative Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2016

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Schedule of Outstanding Copper Swap Contracts

As of September 30, 2016 and December 31, 2015, the Company has outstanding copper swap contracts of the following amounts:

	Units Outstanding (in Pounds)		Net Fair Value - Asset (Liability)
	September 30, 2016	December 31, 2015	September 30, 2016			December 31, 2015
(Amounts in millions)
Cash flow hedges	37.8	17.3	$	(0.5	)	$	(9.8	)
Not designated as hedges	3.7	4.0		(0.4	)		(0.7	)
Total	41.5	21.3	$	(0.9	)	$	(10.5	)

Schedule of Fair Value of Outstanding Copper Swap Contracts Recorded in Balance Sheet

As of September 30, 2016 and December 31, 2015, the fair value of the outstanding copper swap contracts is recorded in the balance sheet as follows:

	September 30, 2016			December 31, 2015
(Dollars in millions)
Other current assets	$	1.9		$	0.1
Accrued liabilities		(2.8	)		(10.6	)
Net liability on balance sheet	$	(0.9	)	$	(10.5	)
Accumulated other comprehensive loss, net of tax	$	0.6		$	6.1

Summary of Amount Recognized in Earnings Related to Copper Swap Contracts

	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
(Dollars in millions)
(Loss) gain from ineffectiveness of cash flow hedges	$	(0.4	)	$	0.0	$	(0.5	)	$	0.3
(Loss) gain from contracts not designated as hedges		0.0			0.0		(0.3	)		0.1
Net	$	(0.4	)	$	0.0	$	(0.8	)	$	0.4

Summary of Net Currency Units Outstanding

As of September 30, 2016 and December 31, 2015, the net currency units outstanding were:

	September 30, 2016		December 31, 2015
(In millions)
British Pounds		GBP 4.7		GBP 5.9
New Zealand Dollars		NZD 18.0		NZD 22.5
United States Dollars		USD 46.8		USD 36.0
Canadian Dollars		CAD 1.2		CAD 4.0

Commitments and Contingent Liabilities (Tables)

9 Months Ended

Sep. 30, 2016

Commitments And Contingencies Disclosure [Abstract]

Changes in Accrued Liability for Environmental Matters

The following table reflects changes in the accrued liability for environmental matters, of which $8.4 million and $7.0 million are classified as current liabilities at September 30, 2016 and December 31, 2015, respectively:

	Period ended
	September 30, 2016			December 31, 2015
(Dollars in millions)
Balance at beginning of year	$	19.8		$	7.8
Expense		0.4			1.2
Reversal of reserves		(0.1	)		(0.5	)
Cash expenditures		(4.0	)		(1.4	)
Acquisition		0.0			13.7
Disposal		(0.5	)		0.0
Currency translation		(0.4	)		(1.0	)
Balance at end of period	$	15.2		$	19.8

Subsidiary Guarantor Information for Koppers Inc. Senior Notes (Tables)

9 Months Ended

Sep. 30, 2016

Text Block [Abstract]

Condensed Consolidating Statement of Operations

For the Three Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	165.7		$	104.7	$	128.9		$	(28.2	)	$	371.1
Cost of sales including depreciation and amortization		0.0			164.0			73.5		103.6			(28.2	)		312.9
Gain on sale of business		0.0			0.0			0.0		(2.1	)		0.0			(2.1	)
Selling, general and administrative		0.5			10.6			13.7		7.8			0.0			32.6
Operating profit (loss)		(0.5	)		(8.9	)		17.5		19.6			0.0			27.7
Other income (loss)		0.0			0.1			0.8		(0.3	)		(0.4	)		0.2
Equity income (loss) of subsidiaries		12.6			33.7			15.2		0.0			(61.5	)		0.0
Interest expense		0.0			11.0			0.0		1.1			(0.4	)		11.7
Income taxes		0.0			1.9			0.0		2.3			0.0			4.2
Income (loss) from continuing operations		12.1			12.0			33.5		15.9			(61.5	)		12.0
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(0.2	)		0.0			(0.2	)
Net income (loss) attributable to Koppers		12.1			12.0			33.5		16.0			(61.5	)		12.1
Comprehensive income (loss) attributable to Koppers		14.3			14.9			35.4		15.6			(65.9	)		14.3

Condensed Consolidating Statement of Operations

For the Three Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	216.7		$	88.7	$	157.9		$	(29.5	)	$	433.8
Cost of sales including depreciation and amortization		0.0			197.6			68.4		139.9			(29.9	)		376.0
Selling, general and administrative		0.4			9.6			10.3		10.5			0.0			30.8
Operating profit (loss)		(0.4	)		9.5			10.0		7.5			0.4			27.0
Other income (loss)		0.0			(2.6	)		1.3		1.8			(0.5	)		0.0
Equity income (loss) of subsidiaries		10.6			16.8			4.8		0.0			(32.2	)		0.0
Interest expense		0.0			11.5			0.0		1.6			(0.5	)		12.6
Income taxes		0.1			1.6			0.3		3.2			0.0			5.2
Income (loss) from continuing operations		10.1			10.6			15.8		4.5			(31.8	)		9.2
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(1.0	)		0.0			(1.0	)
Net income (loss) attributable to Koppers	$	10.1		$	10.6		$	15.8	$	5.4		$	(31.8	)	$	10.1
Comprehensive income (loss) attributable to Koppers	$	(3.5	)	$	(3.0	)	$	1.2	$	(7.9	)	$	9.7		$	(3.5	)

Condensed Consolidating Statement of Operations

For the Nine Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	515.2		$	272.0	$	391.6		$	(75.8	)	$	1,103.0
Cost of sales including depreciation and amortization		0.0			499.8			195.4		326.4			(77.1	)		944.5
Gain on sale of business		0.0			0.0			0.0		(2.1	)		0.0			(2.1	)
Selling, general and administrative		1.3			31.5			27.9		32.4			0.0			93.1
Operating (loss) profit		(1.3	)		(16.1	)		48.7		34.9			1.3			67.5
Other income (loss)		0.0			0.2			3.5		(0.2	)		(1.3	)		2.2
Equity income of subsidiaries		24.2			77.2			23.3		0.0			(124.7	)		0.0
Interest expense		0.0			36.1			0.0		3.5			(1.3	)		38.3
Income taxes		0.0			1.3			0.4		8.8			0.0			10.5
Income from continuing operations		22.9			23.9			75.1		22.4			(123.4	)		20.9
Discontinued operations		0.0			0.0			0.0		0.5			0.0			0.5
Noncontrolling interests		0.0			0.0			0.0		(1.5	)		0.0			(1.5	)
Net income attributable to Koppers	$	22.9		$	23.9		$	75.1	$	24.4		$	(123.4	)	$	22.9
Comprehensive income (loss) attributable to Koppers	$	33.1		$	34.4		$	84.7	$	27.8		$	(146.9	)	$	33.1

Condensed Consolidating Statement of Operations

For the Nine Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Net sales	$	0.0		$	613.7		$	260.4	$	467.1		$	(78.0	)	$	1,263.2
Cost of sales including depreciation and amortization		0.0			583.2			200.0		405.0			(76.5	)		1,111.7
Gain on sale of business		0.0			(3.2	)		0.0		0.0			0.0			(3.2	)
Selling, general and administrative		1.5			31.8			28.9		31.5			0.0			93.7
Operating (loss) profit		(1.5	)		1.9			31.5		30.6			(1.5	)		61.0
Other income (loss)		0.0			0.5			3.3		(1.8	)		(1.6	)		0.4
Equity income (loss) of subsidiaries		16.7			48.7			14.5		0.0			(79.9	)		0.0
Interest expense		0.0			34.6			0.0		5.5			(1.6	)		38.5
Income taxes		(0.5	)		(0.2	)		0.6		10.1			0.0			10.0
Income (loss) from continuing operations		15.7			16.7			48.7		13.2			(81.4	)		12.9
Discontinued operations		0.0			0.0			0.0		(0.1	)		0.0			(0.1	)
Noncontrolling interests		0.0			0.0			0.0		(2.9	)		0.0			(2.9	)
Net income (loss) attributable to Koppers	$	15.7		$	16.7		$	48.7	$	16.0		$	(81.4	)	$	15.7
Comprehensive income (loss) attributable to Koppers	$	(4.8	)	$	(3.8	)	$	25.8	$	(3.3	)	$	(18.7	)	$	(4.8	)

Condensed Consolidating Balance Sheet

September 30, 2016

	Parent		Koppers Inc.		Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
ASSETS
Cash and cash equivalents	$	0.0	$	0.0	$	0.0		$	17.7		$	0.0		$	17.7
Receivables, net		0.0		59.2		34.2			78.0			0.0			171.4
Affiliated receivables		0.0		8.8		9.1			13.1			(31.0	)		0.0
Inventories, net		0.0		101.4		24.1			91.6			(0.9	)		216.2
Loan to related party		0.0		0.0		0.0			9.2			0.3			9.5
Other current assets		0.0		5.9		3.4			20.9			0.0			30.2
Total current assets		0.0		175.3		70.8			230.5			(31.6	)		445.0
Equity investments		20.3		770.8		192.7			(0.1	)		(983.7	)		0.0
Property, plant and equipment, net		0.0		119.4		39.0			118.8			0.0			277.2
Goodwill		0.0		0.8		153.1			33.9			0.0			187.8
Intangible assets, net		0.0		8.0		109.7			28.8			0.0			146.5
Deferred tax assets		0.0		29.8		(2.3	)		6.2			0.0			33.7
Affiliated loan receivables		0.0		41.8		270.6			32.7			(345.1	)		0.0
Other assets		0.0		5.8		4.5			0.3			0.0			10.6
Total assets		20.3		1,151.7		838.1			451.1			(1,360.4	)		1,100.8
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable		0.0		62.5		38.5			40.9			0.0			141.9
Affiliated payables		0.0		20.8		1.5			17.2			(39.5	)		0.0
Accrued liabilities		0.0		42.9		19.7			39.8			0.0			102.4
Current maturities of long-term debt		0.0		30.2		0.0			9.3			0.0			39.5
Total current liabilities		0.0		156.4		59.7			107.2			(39.5	)		283.8
Long-term debt		0.0		608.5		0.0			33.5			0.0			642.0
Affiliated debt		0.0		283.5		22.3			39.3			(345.1	)		0.0
Other long-term liabilities		0.0		83.3		14.1			53.0			(0.1	)		150.3
Total liabilities		0.0		1,131.7		96.1			233.0			(384.7	)		1,076.1
Koppers shareholders’ equity (deficit)		20.3		20.0		742.0			213.7			(975.7	)		20.3
Noncontrolling interests		0.0		0.0		0.0			4.4			0.0			4.4
Total liabilities and equity (deficit)	$	20.3	$	1,151.7	$	838.1		$	451.1		$	(1,360.4	)	$	1,100.8

Condensed Consolidating Balance Sheet

December 31, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Consolidating Adjustments			Consolidated
(Dollars in millions)
ASSETS
Cash and cash equivalents	$	0.0		$	0.1		$	0.7	$	21.0	$	0.0		$	21.8
Receivables, net		0.0			60.4			23.7		75.5		0.0			159.6
Affiliated receivables		0.0			14.3			15.2		4.4		(33.9	)		0.0
Inventories, net		0.0			111.9			24.9		91.8		(2.2	)		226.4
Other current assets		0.0			3.7			1.9		30.9		0.0			36.5
Total current assets		0.0			190.4			66.4		223.6		(36.1	)		444.3
Equity investments		(19.0	)		703.2			165.7		0.0		(849.9	)		0.0
Property, plant and equipment, net		0.0			117.5			41.2		119.1		0.0			277.8
Goodwill		0.0			0.8			153.1		32.7		0.0			186.6
Intangible assets, net		0.0			8.7			117.6		29.8		0.0			156.1
Deferred tax assets		0.0			29.8			0.8		5.7		0.3			36.6
Affiliated loan receivables		0.7			29.6			222.6		31.7		(284.6	)		0.0
Other assets		(0.2	)		4.5			4.9		2.3		0.0			11.5
Total assets	$	(18.5	)	$	1,084.5		$	772.3	$	444.9	$	(1,170.3	)	$	1,112.9
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	$	0.0		$	73.8		$	18.9	$	48.1	$	0.0		$	140.8
Affiliated payables		0.0			16.6			10.9		15.3		(42.8	)		0.0
Accrued liabilities		0.0			35.6			23.4		40.8		0.0			99.8
Current maturities of long-term debt		0.0			30.2			0.0		9.7		0.0			39.9
Total current liabilities		0.0			156.2			53.2		113.9		(42.8	)		280.5
Long-term debt		0.0			647.5			0.0		34.9		0.0			682.4
Affiliated debt		0.0			217.5			29.5		36.9		(283.9	)		0.0
Other long-term liabilities		0.0			81.6			13.2		67.6		0.0			162.4
Total liabilities		0.0			1,102.8			95.9		253.3		(326.7	)		1,125.3
Koppers shareholders’ equity (deficit)		(18.5	)		(18.3	)		676.4		185.5		(843.6	)		(18.5	)
Noncontrolling interests		0.0			0.0			0.0		6.1		0.0			6.1
Total liabilities and equity (deficit)	$	(18.5	)	$	1,084.5		$	772.3	$	444.9	$	(1,170.3	)	$	1,112.9

Condensed Consolidating Statement of Cash Flows

For the Nine Months Ended September 30, 2016

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Cash provided by (used in) operating activities	$	(0.2	)	$	10.8		$	76.1		$	15.7		$	(19.9	)	$	82.5
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions		0.0			(20.0	)		(3.2	)		(9.0	)		0.0			(32.2	)
Repayments (loans to) from affiliates		0.0			(12.2	)		(48.0	)		(1.0	)		61.2			0.0
Net cash (used in) provided by divestitures and asset sales		0.0			0.0			0.7			(5.2	)		0.0			(4.5	)
Net cash provided by (used in) investing activities		0.0			(32.2	)		(50.5	)		(15.2	)		61.2			(36.7	)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt		0.0			(42.5	)		0.0			(0.9	)		0.0			(43.4	)
Borrowings (repayments) of affiliated debt		0.0			66.0			(7.2	)		2.4			(61.2	)		0.0
Deferred financing costs		0.0			(1.4	)		0.0			0.0			0.0			(1.4	)
Dividends paid		0.0			(0.8	)		(19.1	)		0.0			19.9			0.0
Stock repurchased		0.2			0.0			0.0			0.0			0.0			0.2
Net cash provided by (used in) financing activities		0.2			21.3			(26.3	)		1.5			(41.3	)		(44.6	)
Effect of exchange rates on cash		0.0			0.0			0.0			(5.3	)		0.0			(5.3	)
Net increase (decrease) in cash and cash equivalents		0.0			(0.1	)		(0.7	)		(3.3	)		0.0			(4.1	)
Cash and cash equivalents at beginning of year		0.0			0.1			0.7			21.0			0.0			21.8
Cash and cash equivalents at end of period	$	0.0		$	0.0		$	0.0		$	17.7		$	0.0		$	17.7

Condensed Consolidating Statement of Cash Flows

For the Nine Months Ended September 30, 2015

	Parent			Koppers Inc.			Domestic Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidating Adjustments			Consolidated
(Dollars in millions)
Cash provided by (used in) operating activities	$	5.4		$	10.7		$	58.2		$	29.9		$	(9.1	)	$	95.1
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions		0.0			(32.5	)		(4.1	)		(5.1	)		0.0			(41.7	)
Repayments (loans to) from affiliates		0.0			3.8			(49.9	)		(1.4	)		47.5			0.0
Net cash proceeds from divestitures and asset sales		0.0			12.4			2.2			0.1			0.0			14.7
Net cash provided by (used in) investing activities		0.0			(16.3	)		(51.8	)		(6.4	)		47.5			(27.0	)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt		0.0			(87.8	)		0.1			1.4			0.0			(86.3	)
Borrowings (repayments) of affiliated debt		0.0			100.6			(3.9	)		(49.2	)		(47.5	)		0.0
Deferred financing costs		0.0			(1.0	)		0.0			0.0			0.0			(1.0	)
Dividends paid		(5.1	)		(6.2	)		(3.1	)		(3.4	)		9.1			(8.7	)
Stock repurchased		(0.3	)		0.0			0.0			0.0			0.0			(0.3	)
Net cash provided by (used in) financing activities		(5.4	)		5.6			(6.9	)		(51.2	)		(38.4	)		(96.3	)
Effect of exchange rates on cash		0.0			0.1			0.0			10.0			0.0			10.1
Net increase (decrease) in cash and cash equivalents		0.0			0.1			(0.5	)		(17.7	)		0.0			(18.1	)
Cash and cash equivalents at beginning of year		0.0			0.0			0.9			50.2			0.0			51.1
Cash and cash equivalents at end of period	$	0.0		$	0.1		$	0.4		$	32.5		$	0.0		$	33.0

New Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Adjustments for New Accounting Pronouncement [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt issuance cost being reclassified from other assets to long-term debt	$ 9.5	$ 12.5

Plant Closures and Divestitures - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Asset retirement obligation charges		$ 36.2		$ 36.2		$ 46.5			$ 30.5
Gain (loss) on sale of business		2.1	$ 0.0	2.1	$ 3.2
Real estate lease obligations							$ 3.7
North American Utility Pole Business [Member]
Restructuring Cost and Reserve [Line Items]
Gain (loss) on sale of business					$ 3.2
Discontinued Operations Disposed Of By Means Other Than Sale [Member] \| China [Member] \| Koppers Carbon and Chemical Company Limited [Member]
Restructuring Cost and Reserve [Line Items]
Percentage of operations in Tangshan, China owned by the company								60.00%
Severance Charge						0.9
Inventory write-down				0.7
Discontinued Operations Disposed Of By Means Other Than Sale [Member] \| Pennsylvania [Member] \| Carbon Materials and Chemicals [Member]
Restructuring Cost and Reserve [Line Items]
Fixed asset subject to impairment		4.8		4.8
Severance, Inventory write-down, asset retirement obligation and fixed asset impairment charges						18.8
Asset retirement obligation charges		3.8
Discontinued Operations Disposed Of By Means Other Than Sale [Member] \| West Virginia [Member] \| Railroad and Utility Products and Services [Member]
Restructuring Cost and Reserve [Line Items]
Asset retirement obligation charges		0.4		2.3
Severance, asset retirement obligation and fixed asset impairment charges						5.7
Discontinued Operations, Disposed of by Sale [Member] \| United Kingdom [Member]
Restructuring Cost and Reserve [Line Items]
Severance Charge				1.7
Environmental charges						13.9
Asset retirement obligation charges						13.9
Fixed asset subject to impairment						13.9
Gain (loss) on sale of business				2.1
Discontinued Operations, Disposed of by Sale [Member] \| North American Utility Pole Business [Member]
Restructuring Cost and Reserve [Line Items]
Gain (loss) on sale of business	$ 3.2
Asset retirement obligation charges		$ 0.9		2.4
Net cash proceeds from divestitures and asset sales	12.3
Promissory note received	$ 1.3
Long-term lease [Member] \| Wood Protection L.P [Member]
Restructuring Cost and Reserve [Line Items]
Revenues				$ 8.0		$ 14.0

Plant Closures and Divestitures - Summary of Restructuring Activities and Related Reserves (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	$ 18.5	$ 8.1
Accrual	11.3	17.8
Cost charged against assets	(0.7)	(1.3)
Reversal of accrued charges	(10.8)	(0.3)
Cash paid	(8.4)	(5.1)
Currency translation	(0.7)	(0.7)
Reserve, Ending Balance	9.2	18.5
Severance and Employee Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	2.0	0.0
Accrual	2.1	2.2
Cost charged against assets	0.0	0.0
Reversal of accrued charges	(1.8)	0.0
Cash paid	(1.1)	(0.2)
Currency translation	(0.1)	0.0
Reserve, Ending Balance	1.1	2.0
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	4.3	4.1
Accrual	0.0	0.6
Cost charged against assets	0.0	0.0
Reversal of accrued charges	(0.5)	0.0
Cash paid	(1.5)	0.0
Currency translation	0.1	(0.4)
Reserve, Ending Balance	2.4	4.3
Site Demolition [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	12.2	3.9
Accrual	4.8	13.7
Cost charged against assets	0.0	0.0
Reversal of accrued charges	(8.4)	(0.3)
Cash paid	(5.8)	(4.8)
Currency translation	(0.7)	(0.3)
Reserve, Ending Balance	2.1	12.2
Other [Member]
Restructuring Cost and Reserve [Line Items]
Reserve, Beginning Balance	0.0	0.1
Accrual	4.4	1.3
Cost charged against assets	(0.7)	(1.3)
Reversal of accrued charges	(0.1)	0.0
Cash paid	0.0	(0.1)
Currency translation	0.0	0.0
Reserve, Ending Balance	$ 3.6	$ 0.0

Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Loan to related party	$ 9,500,000	$ 9,500,000	$ 9,500,000
Tangshan Koppers Kailuan Carbon Chemical Company Limited [Member]
Related Party Transaction [Line Items]
Loan to related party	$ 9,500,000	$ 9,500,000
Ownership percentage	30.00%	30.00%
Loan repayable beginning date		2015-06
Equity loss recognized from related party	$ 300,000	$ 1,000,000
Provision for loans		0
Tangshan Koppers Kailuan Carbon Chemical Company Limited [Member] \| Loan [Member]
Related Party Transaction [Line Items]
Installment payment defaulted	$ 1,600,000	$ 1,600,000

Fair Value Measurements - Schedule of Company's Financial Instruments (Detail) - USD ($)
$ in Millions

Sep. 30, 2016

Dec. 31, 2015

Fair Value [Member]

Financial assets:

Cash and cash equivalents, including restricted cash

$ 17.7

$ 21.8

Investments and other assets

^[1]

1.1

Financial liabilities:

Long-term debt (including current portion)

691.0

724.6

Carrying Value [Member]

Financial assets:

Cash and cash equivalents, including restricted cash

17.7

21.8

Investments and other assets

^[1]

1.1

Financial liabilities:

Long-term debt (including current portion)

$ 681.5

$ 722.3

[1]	Excludes equity method investments.

Comprehensive Income (Loss) and Equity (Deficit) - Schedule of Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Net income	$ 11.9	$ 9.1	$ 21.4	$ 12.8
Other comprehensive income (loss):
Change in currency translation adjustment	0.7	(13.6)	4.1	(21.9)
Change in unrealized gains (losses) on cash flow hedges, net of tax (expense) benefit of $(1.0), $0.5, $(3.4) and $0.8	1.7	(1.2)	5.5	(1.7)
Change in unrecognized pension net income, net of tax (expense) benefit of $(0.1), $(0.7), $(0.4) and $(2.0)	(0.2)	1.0	0.4	3.0
Change in unrecognized prior service cost	0.0	0.0	0.0	(0.1)
Total comprehensive income (loss)	14.1	(4.7)	31.4	(7.9)
Less: Comprehensive loss attributable to noncontrolling interests	(0.2)	(1.2)	(1.7)	(3.1)
Comprehensive income (loss) attributable to Koppers	$ 14.3	$ (3.5)	$ 33.1	$ (4.8)

Comprehensive Income (Loss) and Equity (Deficit) - Schedule of Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Tax (expense) benefit, derivative financial instrument	$ (1.0)	$ 0.5	$ (3.4)	$ 0.8
Tax (expense) benefit, unrecognized pension net income	$ (0.1)	$ (0.7)	$ (0.4)	$ (2.0)

Comprehensive Income (Loss) and Equity (Deficit) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Loss related to derivative instrument	$ 1.6	$ 1.8	$ 4.8	$ 3.7

Comprehensive Income (Loss) and Equity (Deficit) - Schedule of Change in Equity (Deficit) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			$ (12.4)	$ 83.9
Net income (loss)	$ 11.9	$ 9.1	21.4	12.8
Employee stock plans			6.0	3.1
Other comprehensive income			10.0	(20.7)
Dividends				(3.5)
Repurchases of common stock			(0.3)	(0.3)
Balance	24.7	75.3	24.7	75.3
Total Koppers Shareholders' Equity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(18.5)	70.0
Net income (loss)			22.9	15.7
Employee stock plans			6.0	3.1
Other comprehensive income			10.2	(20.5)
Dividends				0.0
Repurchases of common stock			(0.3)	(0.3)
Balance	20.3	68.0	20.3	68.0
Noncontrolling Interests [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			6.1	13.9
Net income (loss)			(1.5)	(2.9)
Employee stock plans			0.0	0.0
Other comprehensive income			(0.2)	(0.2)
Dividends				(3.5)
Repurchases of common stock			0.0	0.0
Balance	$ 4.4	$ 7.3	$ 4.4	$ 7.3

Earnings per Common Share - Schedule of Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income attributable to Koppers	$ 12.1	$ 10.1	$ 22.9	$ 15.7
Less: (Loss) income from discontinued operations	(0.1)	(0.1)	0.5	(0.1)
Income from continuing operations attributable to Koppers	$ 12.2	$ 10.2	$ 22.4	$ 15.8
Weighted average common shares outstanding:
Basic	20,657	20,553	20,627	20,537
Effect of dilutive securities	506	79	348	72
Diluted	21,163	20,632	20,975	20,609
Income per common share – continuing operations:
Basic income per common share	$ 0.59	$ 0.49	$ 1.08	$ 0.77
Diluted income per common share	$ 0.58	$ 0.49	$ 1.07	$ 0.76
Other data:
Antidilutive securities excluded from computation of diluted earnings per common share	339	738	421	671

Stock-based Compensation - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future gross compensation expense related to non-vested stock-based compensation arrangements, which are expected to vest	$ 12.9
Future compensation expense, weighted-average expected period of recognition in months	28 months
Restricted Stock Units (RSUs) [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period	1 year
Restricted Stock Units (RSUs) [Member] \| March 2015 and 2016 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period	4 years
Performance Stock Units [Member] \| March 2015 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period		3 years
Percentage of target award earned by participants		200.00%
Vesting performance stock units if minimum performance criteria are not achieved		0
Stock options, term in years		3 years
Performance Stock Units [Member] \| March 2015 Grant [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target award earned by participants		0.00%
Performance Stock Units [Member] \| March 2015 Grant [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target award earned by participants		150.00%
Performance Stock Units [Member] \| March 2016 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period	3 years
Vesting performance stock units if minimum performance criteria are not achieved	0
Stock options, term in years	3 years
Performance Stock Units [Member] \| March 2016 Grant [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target award earned by participants	0.00%
Performance Stock Units [Member] \| March 2016 Grant [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target award earned by participants	200.00%
Employee Stock Option [Member] \| March 2015 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, term in years	10 years
Employee Stock Option [Member] \| Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period	4 years
Employee Stock Option [Member] \| Executive Officer \| March 2015 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based awards, vesting period	3 years

Stock-based Compensation - Performance Award Fair Value Assumptions (Detail) - March 2015 Grant [Member]	9 Months Ended
	Sep. 30, 2016 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share	$ 17.57
Expected dividend yield per share	3.40%
Expected volatility	42.27%
Risk-free interest rate	1.73%
Grant date fair value per share	$ 5.20
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share	$ 18.11
Expected dividend yield per share	0.00%
Expected volatility	40.86%
Risk-free interest rate	0.96%
Look-back period in years	2 years 10 months 2 days
Grant date fair value per share	$ 23.70

Stock-based Compensation - Summary of Performance Stock Units (Detail) - shares	Sep. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	836,797	610,607
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	557,551	397,399
Minimum [Member] \| 2014 - 2016 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	0
Minimum [Member] \| 2015 - 2017 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	0
Minimum [Member] \| 2016 - 2018 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	0
Target Shares [Member] \| 2014 - 2016 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	87,262
Target Shares [Member] \| 2015 - 2017 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	205,082
Target Shares [Member] \| 2016 - 2018 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	262,622
Maximum [Member] \| 2014 - 2016 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	130,893
Maximum [Member] \| 2015 - 2017 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	410,164
Maximum [Member] \| 2016 - 2018 [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding	525,244

Stock-based Compensation - Summary of Status and Activity of Non-Vested Stock Awards (Detail)	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Beginning Balance	610,607
Granted	437,263
Credited from dividends	2,662
Vested	(96,950)
Forfeited	(116,785)
Non-vested, Ending Balance	836,797
Beginning Balance, Non-vested, Weighted Average Grant Date Fair Value per Unit \| $ / shares	$ 27.29
Granted, Weighted Average Grant Date Fair Value per Unit \| $ / shares	22.02
Credited from dividends, Weighted Average Grant Date Fair Value per Unit \| $ / shares	25.47
Vested, Weighted Average Grant Date Fair Value per Unit \| $ / shares	28.93
Forfeited, Weighted Average Grant Date Fair Value per Unit \| $ / shares	37.30
Ending Balance, Non-vested, Weighted Average Grant Date Fair Value per Unit \| $ / shares	$ 22.95
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Beginning Balance	213,208
Granted	172,282
Credited from dividends	950
Vested	(96,950)
Forfeited	(10,244)
Non-vested, Ending Balance	279,246
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Beginning Balance	397,399
Granted	264,981
Credited from dividends	1,712
Vested	0
Forfeited	(106,541)
Non-vested, Ending Balance	557,551

Stock-based Compensation - Stock Options Fair Value Assumptions (Detail)	9 Months Ended
	Sep. 30, 2016 $ / shares
March 2016 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share	$ 18.11
Expected dividend yield per share	0.00%
Expected life in years	5 years 11 months 16 days
Expected volatility	40.86%
Risk-free interest rate	1.45%
Grant date fair value per share	$ 7.41
March 2015 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share	$ 17.57
Expected dividend yield per share	3.40%
Expected life in years	5 years 9 months
Expected volatility	42.27%
Risk-free interest rate	1.73%
Grant date fair value per share	$ 5.20
February 2014 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share	$ 37.93
Expected dividend yield per share	2.75%
Expected life in years	6 years 6 months
Expected volatility	52.14%
Risk-free interest rate	1.98%
Grant date fair value per share	$ 15.26

Stock-based Compensation - Summary of Status and Activity of Stock Options (Detail) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options, Outstanding at December 31, 2015 \| shares	774,249
Options, Granted \| shares	211,193
Options, Exercised \| shares	(14,301)
Options, Forfeited \| shares	(19,539)
Options, Outstanding at September 30, 2016 \| shares	951,602
Options, Exercisable at September 30, 2016 \| shares	452,730
Weighted Average Exercise Price per Option, Outstanding at December 31, 2015 \| $ / shares	$ 28.46
Weighted Average Exercise Price per Option, Granted \| $ / shares	18.11
Weighted Average Exercise Price per Option, Exercised \| $ / shares	26.02
Weighted Average Exercise Price per Option, Forfeited \| $ / shares	23.70
Weighted Average Exercise Price per Option, Outstanding at September 30, 2016 \| $ / shares	26.29
Weighted Average Exercise Price per Option, Exercisable at September 30, 2016 \| $ / shares	$ 33.24
Weighted Average Remaining Contractual Term, Outstanding at September 30, 2016	6 years 9 months
Weighted Average Remaining Contractual Term, Exercisable at September 30, 2016	4 years 5 months 27 days
Aggregate Intrinsic Value, Outstanding at September 30, 2016 \| $	$ 3.3
Aggregate Intrinsic Value, Exercisable at September 30, 2016 \| $	$ 1.7

Stock-based Compensation - Schedule of Stock-Based Compensation Expense Recognized (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stock-based compensation expense recognized:
Less related income tax benefit	$ 1.0	$ 0.4	$ 2.3	$ 1.2
Decrease in net income attributable to Koppers	1.3	0.7	3.4	1.9
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense recognized:
Stock-based compensation expense	$ 2.3	$ 1.1	$ 5.7	$ 3.1

Segment Information - Additional Information (Detail)	9 Months Ended
Segment Information - Additional Information (Detail)	Sep. 30, 2016 Segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segment Information - Summary of Results of Segment Operations (Detail) - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Sep. 30, 2016

Sep. 30, 2015

Sep. 30, 2016

Sep. 30, 2015

Revenues from external customers:

Net sales

$ 371.1

$ 433.8

$ 1,103.0

$ 1,263.2

Depreciation and amortization expense

13.8

15.5

42.0

45.2

Operating profit (loss)

27.7

27.0

67.5

61.0

Operating Segments [Member] | Railroad and Utility Products and Services [Member]

Revenues from external customers:

Net sales

145.7

177.6

461.5

506.6

Depreciation and amortization expense

^[1]

2.9

3.6

9.9

11.1

Operating profit (loss)

^[2]

14.9

17.7

46.9

48.1

Operating Segments [Member] | Carbon Materials and Chemicals [Member]

Revenues from external customers:

Net sales

117.8

163.0

337.5

479.6

Depreciation and amortization expense

^[3]

6.2

7.2

17.8

19.9

Operating profit (loss)

^[4]

(3.9)

0.0

(29.8)

(13.8)

Operating Segments [Member] | Performance Chemicals [Member]

Revenues from external customers:

Net sales

107.6

93.2

304.0

277.0

Depreciation and amortization expense

4.7

14.3

14.2

Operating profit (loss)

17.6

9.7

52.6

31.6

Intersegment [Member]

Revenues from external customers:

Net sales

28.5

25.1

74.3

69.9

Intersegment [Member] | Carbon Materials and Chemicals [Member]

Revenues from external customers:

Net sales

26.2

23.1

68.1

63.6

Intersegment [Member] | Performance Chemicals [Member]

Revenues from external customers:

Net sales

2.3

2.0

6.2

6.3

Corporate, Non-Segment [Member]

Revenues from external customers:

Operating profit (loss)

^[5]

$ (0.9)

$ (0.4)

$ (2.2)

$ (4.9)

[1]	Excludes impairment charges of $2.5 million for the nine months ended September 30, 2015 for a wood treating facility in the United States.
[2]	Includes gain on sale of the Company’s North American utility pole business of $3.2 million and impairment charges of $2.5 million for the nine months ended September 30, 2015.
[3]	Excludes impairment charges of $3.5 million for the three and nine months ended September 30, 2016 for a coal tar distillation facility in the United States.
[4]	Includes gain on sale of the Company’s United Kingdom coal tar distillation business of $2.1 million and impairment charges of $3.5 million for the three and nine months ended September 30, 2016.
[5]	Operating loss for Corporate includes general and administrative costs for Koppers Holdings Inc., the parent company of Koppers Inc., and foreign exchange revaluation related to intercompany loans in connection with a legal reorganization of the Company.

Segment Information - Summary of Results of Segment Operations (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue from External Customer [Line Items]
Impairment charges			$ 3.5	$ 7.1
Gain (loss) on sale of business	$ 2.1	$ 0.0	2.1	3.2
North American Utility Pole Business [Member]
Revenue from External Customer [Line Items]
Impairment charges				2.5
Gain (loss) on sale of business				3.2
United Kingdom Coal Tar Distillation Business [Member]
Revenue from External Customer [Line Items]
Impairment charges	3.5		3.5
Gain (loss) on sale of business	2.1		2.1
Wood Treating Facility [Member] \| United States [Member]
Revenue from External Customer [Line Items]
Impairment charges				$ 2.5
Coal Tar Distillation Facility [Member] \| United States [Member]
Revenue from External Customer [Line Items]
Impairment charges	$ 3.5		$ 3.5

Segment Information - Summary of Tangible and Intangible Assets by Segments (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting Asset Reconciling Item [Line Items]
Assets	$ 1,100.8	$ 1,112.9
Goodwill	187.8	186.6
Railroad and Utility Products and Services [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets	271.4	254.1
Goodwill	10.2	9.9
Carbon Materials and Chemicals [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets	336.5	368.4
Performance Chemicals [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets	447.3	441.3
Goodwill	177.6	176.7
All Other [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets	$ 45.6	$ 49.1

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Estimated annual effective income tax rate	29.10%	33.10%
Income taxes as a percentage of pretax income	33.40%	43.70%
Net tax benefit included in income taxes, discrete items		$ 1.6
Unrecognized tax benefits with impact on the effective tax rate	$ 5.4		$ 5.2
Unrecognized tax benefits	7.5		7.7
Accrued interest expense and penalties	$ 3.4		$ 3.0

Income Taxes - Summary of Income Taxes Reconciled with Federal Statutory Rate (Detail)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Federal income tax rate	35.00%	35.00%
State income taxes, net of federal tax benefit	1.80%	(0.80%)
Foreign earnings taxed at different rates	(9.40%)	(3.70%)
Change in tax contingency reserves	0.60%	1.20%
Nondeductible expenses	1.20%	1.40%
Tax credits	(0.40%)	(0.00%)
Other	0.30%	0.00%
Estimated annual effective income tax rate	29.10%	33.10%

Inventories - Components of Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 154.2	$ 169.8
Work in process	15.9	15.5
Finished goods	98.4	97.4
Inventories, gross	268.5	282.7
Less revaluation to LIFO	52.3	56.3
Net	$ 216.2	$ 226.4

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 791.5	$ 786.0
Less accumulated depreciation	514.3	508.2
Net	277.2	277.8
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	17.4	17.6
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	61.9	62.8
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 712.2	$ 705.6

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment [Line Items]
Impairment charges		$ 3.5	$ 7.1
Carbon Materials and Chemicals [Member] \| Coal Tar Distillation Plant [Member]
Property, Plant and Equipment [Line Items]
Impairment charges	$ 3.5	$ 3.5
Railroad and Utility Products and Services [Member] \| Wood Treating Plant [Member]
Property, Plant and Equipment [Line Items]
Impairment charges			$ 2.5

Pensions and Postretirement Benefit Plans - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 Plan Participant
Defined Benefit Plan Disclosure [Line Items]
Number of domestic non-qualified defined benefit plans \| Plan		3
U.S. Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of salaried terminated deferred vested participants \| Participant		400
U.S. Defined Benefit Pension Plan [Member] \| Scenario Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated total amount to be paid out of defined benefit plan assets	$ 14.0
Estimated pension settlement loss	$ (4.5)

Pensions and Post-retirement Benefit Plans - Components of Net Periodic Benefit Cost for Pension Plans and Other Benefit Plans (Detail) - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Sep. 30, 2016

Sep. 30, 2015

Sep. 30, 2016

Sep. 30, 2015

Postemployment Benefits [Abstract]

Service cost

$ 0.4

$ 0.5

$ 1.3

$ 1.5

Interest cost

2.7

8.3

8.1

Expected return on plan assets

(2.6)

(3.0)

(7.9)

(9.0)

Amortization of prior service cost

0.0

(0.1)

0.0

(0.2)

Amortization of net loss

0.5

1.7

5.0

Net periodic benefit cost

1.0

1.8

3.4

5.4

Defined contribution plan expense

^[1]

$ 2.0

$ 2.1

$ 5.8

$ 4.2

[1]	The nine months ended September 30, 2015 includes reversal of 2014 discretionary 401k match accrual of $2.2 million.

Pensions and Post-retirement Benefit Plans - Components of Net Periodic Benefit Cost for Pension Plans and Other Benefit Plans (Parenthetical) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Postemployment Benefits [Abstract]
Reversal of 2014 discretionary 401k match accrual	$ 2.2

Debt - Schedule of Long-Term Debt Instruments (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Dec. 01, 2009
Debt Instrument [Line Items]
Total debt	$ 691.0	$ 734.8
Less short term debt and current maturities of long-term debt	39.5	39.9
Less unamortized debt issuance costs	9.5	12.5
Long-term debt	$ 642.0	682.4
Senior Secured Credit Facilities [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	4.30%
Debt, Maturity	2019
Total debt	$ 240.0	262.5
Senior Secured Credit Facilities [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	4.30%
Debt, Maturity	2019
Total debt	$ 110.0	130.0
Committed Loan Facility Agreements [Member] \| Construction Loans [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	4.76%
Debt, Maturity	2018
Total debt	$ 43.0	44.8
7 7/8 Percent Senior Notes Due 2019 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	7.875%		7.875%
Debt, Maturity	2019
Total debt	$ 298.0	$ 297.5

Debt - Additional Information (Detail) ¥ in Millions						1 Months Ended	9 Months Ended
Debt - Additional Information (Detail) ¥ in Millions	Dec. 01, 2016	Apr. 08, 2016 USD ($)	Aug. 15, 2014 USD ($)	Nov. 18, 2013 USD ($)	Dec. 01, 2009 USD ($)	Dec. 21, 2015 Installment	Sep. 30, 2016 USD ($)	Nov. 18, 2013 CNY (¥)
Senior Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Revolving credit facility, borrowing maturity date			Aug. 15, 2019
Letters of credit, amount outstanding							$ 41,700,000
Senior Secured Credit Facilities [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility		$ 300,000,000	$ 500,000,000
Deferred financing costs to be written off		$ 2,000,000
Debt instrument, unused borrowing capacity							$ 148,300,000
Debt, Weighted Average Interest Rate							4.30%
Senior Secured Credit Facilities [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility			$ 300,000,000
Quarterly principal repayment obligations, interest rate			2.50%
Quarterly principal repayment obligations			$ 7,500,000
Committed Loan Facility Agreements [Member] \| Construction Loans [Member]
Debt Instrument [Line Items]
Debt maturity date						Dec. 21, 2020
Number of installments for repayment of loans \| Installment						6
Installment frequency for repayment of loans						6 months
Commencement period of debt repayment						2018-06
Debt, Weighted Average Interest Rate							4.76%
Committed Loan Facility Agreements [Member] \| Construction Loans [Member] \| Third Party Debt [Member]
Debt Instrument [Line Items]
Construction loan facility borrowing capacity \| ¥								¥ 198.8
Committed Loan Facility Agreements [Member] \| Construction Loans [Member] \| Committed Credit Facility [Member] \| Lender [Member]
Debt Instrument [Line Items]
Construction loan facility borrowing capacity \| ¥								66.2
Committed Loan Facility Agreements [Member] \| Construction Loans [Member] \| Koppers Carbon and Chemical Company Limited [Member]
Debt Instrument [Line Items]
Percentage ownership of subsidiary				75.00%
Construction loan facility borrowing capacity				$ 44,000,000				¥ 265.0
Percentage of non-controlling shareholders				25.00%				25.00%
7 7/8 Percent Senior Notes Due 2019 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate					7.875%		7.875%
Debt instrument, issuance date							Dec. 01, 2009
Debt instrument, offering price percentage					98.311%
Debt instrument, offering value					$ 294,900,000
Principal value of Senior Notes					$ 300,000,000
Debt instrument, effective interest rate					8.125%
Debt instrument, redemption price percentage							102.625%
Frequency of interest payment on senior notes							Interest on the Senior Notes is payable semiannually on December 1 and June 1 each year
7 7/8 Percent Senior Notes Due 2019 [Member] \| Senior Notes [Member] \| Scenario Forecast [Member]
Debt Instrument [Line Items]
Debt instrument, redemption price percentage	101.313%

Asset Retirement Obligations - Schedule of Changes in Carrying Values of Asset Retirement Obligations (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation at beginning of year	$ 46.5	$ 30.5
(Divestiture) acquisition	(8.0)	0.7
Accretion expense	6.2	3.7
Revision in estimated cash flows	0.9	24.4
Cash expenditures	(8.7)	(12.1)
Currency translation	(0.7)	(0.7)
Balance at end of period	$ 36.2	$ 46.5

Deferred Revenue - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2016
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 29.1	$ 27.6
China [Member]
Deferred Revenue Arrangement [Line Items]
Agreement period	50 years

- Definition

The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Deferred Revenue - Deferred Revenue from Extended Product Warranty Liabilities (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Deferred Revenue Disclosure [Abstract]
Deferred revenue at beginning of year	$ 30.1	$ 2.5
Advance payment	0.0	30.0
Revenue earned	(0.6)	(1.0)
Currency translation	(0.8)	(1.4)
Deferred revenue at end of year	$ 28.7	$ 30.1

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Maximum period hedged in cash flow hedge	30 months
Unrealized losses, reclassification period	12 months
Unrealized losses, net of tax, expected to be reclassified from other comprehensive income (loss)into earnings	$ 0.7
Not Designated as Hedging Instrument \| Forward Contracts [Member]
Derivative [Line Items]
Net Fair Value - Asset (Liability)	(1.3)
Accrued Liabilities [Member] \| Not Designated as Hedging Instrument \| Forward Contracts [Member]
Derivative [Line Items]
Net Fair Value - Asset (Liability)		$ (1.9)
Gross derivative liability	1.5
Other Current Assets [Member] \| Not Designated as Hedging Instrument \| Forward Contracts [Member]
Derivative [Line Items]
Gross derivative assets	$ 0.2

Derivative Financial Instruments - Outstanding Copper Swap Contracts (Detail) - Copper Swap Contracts[Member] £ in Millions, $ in Millions	Sep. 30, 2016 USD ($)	Sep. 30, 2016 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 GBP (£)
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding \| £		£ 41.5		£ 21.3
Net Fair Value - Asset (Liability) \| $	$ (0.9)		$ (10.5)
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding \| £		37.8		17.3
Net Fair Value - Asset (Liability) \| $	(0.5)		(9.8)
Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Copper Swap Contracts Units Outstanding \| £		£ 3.7		£ 4.0
Net Fair Value - Asset (Liability) \| $	$ (0.4)		$ (0.7)

Derivative Financial Instruments - Schedule of Fair Value of Outstanding Copper Swap Contracts Recorded in Balance Sheet (Detail) - Copper Swap Contracts[Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Net Fair Value - Asset (Liability)	$ (0.9)	$ (10.5)
Accumulated other comprehensive loss, net of tax	0.6	6.1
Other Current Assets [Member]
Derivative [Line Items]
Net Fair Value - Asset (Liability)	1.9	0.1
Accrued Liabilities [Member]
Derivative [Line Items]
Net Fair Value - Asset (Liability)	$ (2.8)	$ (10.6)

Derivative Financial Instruments - Schedule of Amounts Recognized In Earnings Related To Copper Swap Contracts (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Copper Swap Contracts[Member]
Derivative [Line Items]
(Loss) gain from contracts not designated as hedges	$ 0.0	$ 0.0	$ (0.3)	$ 0.1
Net	(0.4)	0.0	(0.8)	0.4
Cash Flow Hedging [Member]
Derivative [Line Items]
(Loss) gain from ineffectiveness of cash flow hedges	$ (0.4)	$ 0.0	$ (0.5)	$ 0.3

Derivative Financial Instruments - Schedule Of Net Currency Units Outstanding (Detail)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 GBP (£)	Sep. 30, 2016 NZD ($)	Sep. 30, 2016 CAD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 NZD ($)	Dec. 31, 2015 CAD ($)
Offsetting [Abstract]
Net currency units outstanding	$ 46,800,000	£ 4,700,000	$ 18,000,000	$ 1,200,000	$ 36,000,000	£ 5,900,000	$ 22,500,000	$ 4,000,000

Commitments and Contingent Liabilities - Additional Information (Detail)	1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2004 USD ($)	Sep. 30, 2016 USD ($) State Plaintiff Case Owner site Party Plant mi	Dec. 31, 2015 USD ($) Plaintiff Case	Jun. 30, 2016 USD ($)	Dec. 31, 2014 USD ($)
Loss Contingencies [Line Items]
Number of states with new claims filed \| State		2
Number of plaintiffs \| Plaintiff		103	110
Environmental remediation and regulation liability		$ 15,200,000	$ 19,800,000		$ 7,800,000
Accrued liability for environmental matters, current		8,400,000	$ 7,000,000
Portland Harbor and Newark Bay CERCLA sites [Member]
Loss Contingencies [Line Items]
Environmental remediation and regulation liability		0
Costs of participating in PRP group		$ 900,000
Beazer East [Member]
Loss Contingencies [Line Items]
Environmental legal indemnification expense	$ 7,000,000
Sites listed on National Priorities List \| site		1
Compensatory Damages [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		55
Punitive Damages [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		50
Indemnification Agreement [Member] \| Beazer East [Member]
Loss Contingencies [Line Items]
Environmental remediation costs paid by others, per year		$ 10,000,000
Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		55	59
Reserve for legal proceedings		$ 0
Gainesville Class Action Complaint [Member]
Loss Contingencies [Line Items]
Reserve for legal proceedings		$ 0
Single family residential properties extension sought by plaintiffs from former plant area \| mi		2
Single family residential properties, number of owners \| Owner		7,000
Pennsylvania [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		54
Pennsylvania [Member] \| Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		54
Tennessee [Member] \| Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases \| Case		1
Compensatory damages		$ 15,000,000
Oregon [Member] \| Portland Harbor CERCLA site [Member]
Loss Contingencies [Line Items]
Number of potential responsible parties \| Party		80
Net present value of proposed remedy estimation		$ 800,000,000
Undiscounted cost of proposed remedy estimation		1,200,000,000
United States [Member] \| Osmose Holdings, Inc. [Member]
Loss Contingencies [Line Items]
Environmental remediation and regulation liability		$ 5,100,000
Number of plant sites \| Plant		2
United Kingdom And Australia [Member] \| Osmose Holdings, Inc. [Member]
Loss Contingencies [Line Items]
Environmental legal indemnification expense		$ 5,000,000
Environmental remediation and regulation liability		$ 5,700,000
Number of plant sites \| Plant		3
Amount contributable by third party		$ 2,700,000
United Kingdom [Member] \| Osmose Holdings, Inc. [Member]
Loss Contingencies [Line Items]
Amount contributable by third party				$ 2,900,000
Australia [Member] \| Continental Carbon facility [Member]
Loss Contingencies [Line Items]
Environmental remediation and regulation liability		$ 2,400,000

Commitments and Contingent Liabilities - Changes in Accrued Liability for Environmental Matters (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Balance at beginning of year	$ 19.8	$ 7.8
Expense	0.4	1.2
Reversal of reserves	(0.1)	(0.5)
Cash expenditures	(4.0)	(1.4)
Acquisition	0.0	13.7
Disposal	(0.5)	0.0
Currency translation	(0.4)	(1.0)
Balance at end of period	$ 15.2	$ 19.8

Subsidiary Guarantor Information for Koppers Inc. Senior Notes - Additional Information (Detail) - USD ($)		9 Months Ended
	Dec. 01, 2009	Sep. 30, 2016	Sep. 30, 2015
7 7/8 Percent Senior Notes Due 2019 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Principal value of Senior Notes	$ 300,000,000
Domestic Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Cash dividends paid		$ 1,100,000	$ 6,200,000
Domestic Guarantor Subsidiaries [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		300,000,000
Domestic Guarantor Subsidiaries [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		247,500,000
Domestic Guarantor Subsidiaries [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Percentage ownership of subsidiary	100.00%
Koppers Inc. [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Net assets		$ 20,000,000

Subsidiary Guarantor Information for Koppers Inc. Senior Notes - Condensed Consolidating Statement of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Statement Of Income Captions [Line Items]
Net sales	$ 371.1	$ 433.8	$ 1,103.0	$ 1,263.2
Cost of sales including depreciation and amortization	312.9	376.0	944.5	1,111.7
Gain on sale of business	(2.1)	0.0	(2.1)	(3.2)
Selling, general and administrative	32.6	30.8	93.1	93.7
Operating profit	27.7	27.0	67.5	61.0
Other income (loss)	0.2	0.0	2.2	0.4
Equity income (loss) of subsidiaries	0.0	0.0	0.0	0.0
Interest expense	11.7	12.6	38.3	38.5
Income taxes	4.2	5.2	10.5	10.0
Income from continuing operations	12.0	9.2	20.9	12.9
Discontinued operations	(0.1)	(0.1)	0.5	(0.1)
Noncontrolling interests	(0.2)	(1.0)	(1.5)	(2.9)
Net income attributable to Koppers	12.1	10.1	22.9	15.7
Comprehensive income (loss) attributable to Koppers	14.3	(3.5)	33.1	(4.8)
Consolidation Eliminations [Member]
Condensed Statement Of Income Captions [Line Items]
Net sales	(28.2)	(29.5)	(75.8)	(78.0)
Cost of sales including depreciation and amortization	(28.2)	(29.9)	(77.1)	(76.5)
Gain on sale of business	0.0		0.0	0.0
Selling, general and administrative	0.0	0.0	0.0	0.0
Operating profit	0.0	0.4	1.3	(1.5)
Other income (loss)	(0.4)	(0.5)	(1.3)	(1.6)
Equity income (loss) of subsidiaries	(61.5)	(32.2)	(124.7)	(79.9)
Interest expense	(0.4)	(0.5)	(1.3)	(1.6)
Income taxes	0.0	0.0	0.0	0.0
Income from continuing operations	(61.5)	(31.8)	(123.4)	(81.4)
Discontinued operations	0.0	0.0	0.0	0.0
Noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Koppers	(61.5)	(31.8)	(123.4)	(81.4)
Comprehensive income (loss) attributable to Koppers	(65.9)	9.7	(146.9)	(18.7)
Parent [Member] \| Reportable Legal Entities [Member]
Condensed Statement Of Income Captions [Line Items]
Net sales	0.0	0.0	0.0	0.0
Cost of sales including depreciation and amortization	0.0	0.0	0.0	0.0
Gain on sale of business	0.0		0.0	0.0
Selling, general and administrative	0.5	0.4	1.3	1.5
Operating profit	(0.5)	(0.4)	(1.3)	(1.5)
Other income (loss)	0.0	0.0	0.0	0.0
Equity income (loss) of subsidiaries	12.6	10.6	24.2	16.7
Interest expense	0.0	0.0	0.0	0.0
Income taxes	0.0	0.1	0.0	(0.5)
Income from continuing operations	12.1	10.1	22.9	15.7
Discontinued operations	0.0	0.0	0.0	0.0
Noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Koppers	12.1	10.1	22.9	15.7
Comprehensive income (loss) attributable to Koppers	14.3	(3.5)	33.1	(4.8)
Koppers Inc. [Member] \| Reportable Legal Entities [Member]
Condensed Statement Of Income Captions [Line Items]
Net sales	165.7	216.7	515.2	613.7
Cost of sales including depreciation and amortization	164.0	197.6	499.8	583.2
Gain on sale of business	0.0		0.0	(3.2)
Selling, general and administrative	10.6	9.6	31.5	31.8
Operating profit	(8.9)	9.5	(16.1)	1.9
Other income (loss)	0.1	(2.6)	0.2	0.5
Equity income (loss) of subsidiaries	33.7	16.8	77.2	48.7
Interest expense	11.0	11.5	36.1	34.6
Income taxes	1.9	1.6	1.3	(0.2)
Income from continuing operations	12.0	10.6	23.9	16.7
Discontinued operations	0.0	0.0	0.0	0.0
Noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Koppers	12.0	10.6	23.9	16.7
Comprehensive income (loss) attributable to Koppers	14.9	(3.0)	34.4	(3.8)
Domestic Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Condensed Statement Of Income Captions [Line Items]
Net sales	104.7	88.7	272.0	260.4
Cost of sales including depreciation and amortization	73.5	68.4	195.4	200.0
Gain on sale of business	0.0		0.0	0.0
Selling, general and administrative	13.7	10.3	27.9	28.9
Operating profit	17.5	10.0	48.7	31.5
Other income (loss)	0.8	1.3	3.5	3.3
Equity income (loss) of subsidiaries	15.2	4.8	23.3	14.5
Interest expense	0.0	0.0	0.0	0.0
Income taxes	0.0	0.3	0.4	0.6
Income from continuing operations	33.5	15.8	75.1	48.7
Discontinued operations	0.0	0.0	0.0	0.0
Noncontrolling interests	0.0	0.0	0.0	0.0
Net income attributable to Koppers	33.5	15.8	75.1	48.7
Comprehensive income (loss) attributable to Koppers	35.4	1.2	84.7	25.8
Non-Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Condensed Statement Of Income Captions [Line Items]
Net sales	128.9	157.9	391.6	467.1
Cost of sales including depreciation and amortization	103.6	139.9	326.4	405.0
Gain on sale of business	(2.1)		(2.1)	0.0
Selling, general and administrative	7.8	10.5	32.4	31.5
Operating profit	19.6	7.5	34.9	30.6
Other income (loss)	(0.3)	1.8	(0.2)	(1.8)
Equity income (loss) of subsidiaries	0.0	0.0	0.0	0.0
Interest expense	1.1	1.6	3.5	5.5
Income taxes	2.3	3.2	8.8	10.1
Income from continuing operations	15.9	4.5	22.4	13.2
Discontinued operations	(0.1)	(0.1)	0.5	(0.1)
Noncontrolling interests	(0.2)	(1.0)	(1.5)	(2.9)
Net income attributable to Koppers	16.0	5.4	24.4	16.0
Comprehensive income (loss) attributable to Koppers	$ 15.6	$ (7.9)	$ 27.8	$ (3.3)

Subsidiary Guarantor Information for Koppers Inc. Senior Notes - Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 17.7	$ 21.8	$ 33.0	$ 51.1
Receivables, net	171.4	159.6
Affiliated receivables	0.0	0.0
Inventories, net	216.2	226.4
Loan to related party	9.5	9.5
Other current assets	30.2	36.5
Total current assets	445.0	444.3
Equity investments	0.0	0.0
Property, plant and equipment, net	277.2	277.8
Goodwill	187.8	186.6
Intangible assets, net	146.5	156.1
Deferred tax assets	33.7	36.6
Affiliated loan receivables	0.0	0.0
Other assets	10.6	11.5
Total assets	1,100.8	1,112.9
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	141.9	140.8
Affiliated payables	0.0	0.0
Accrued liabilities	102.4	99.8
Current maturities of long-term debt	39.5	39.9
Total current liabilities	283.8	280.5
Long-term debt	642.0	682.4
Affiliated debt	0.0	0.0
Other long-term liabilities	150.3	162.4
Total liabilities	1,076.1	1,125.3
Koppers shareholders’ equity (deficit)	20.3	(18.5)
Noncontrolling interests	4.4	6.1
Total liabilities and equity (deficit)	1,100.8	1,112.9
Consolidation Eliminations [Member]
Assets
Cash and cash equivalents	0.0	0.0	0.0	0.0
Receivables, net	0.0	0.0
Affiliated receivables	(31.0)	(33.9)
Inventories, net	(0.9)	(2.2)
Loan to related party	0.3
Other current assets	0.0	0.0
Total current assets	(31.6)	(36.1)
Equity investments	(983.7)	(849.9)
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Deferred tax assets	0.0	0.3
Affiliated loan receivables	(345.1)	(284.6)
Other assets	0.0	0.0
Total assets	(1,360.4)	(1,170.3)
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	0.0	0.0
Affiliated payables	(39.5)	(42.8)
Accrued liabilities	0.0	0.0
Current maturities of long-term debt	0.0	0.0
Total current liabilities	(39.5)	(42.8)
Long-term debt	0.0	0.0
Affiliated debt	(345.1)	(283.9)
Other long-term liabilities	(0.1)	0.0
Total liabilities	(384.7)	(326.7)
Koppers shareholders’ equity (deficit)	(975.7)	(843.6)
Noncontrolling interests	0.0	0.0
Total liabilities and equity (deficit)	(1,360.4)	(1,170.3)
Parent [Member] \| Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0.0	0.0	0.0	0.0
Receivables, net	0.0	0.0
Affiliated receivables	0.0	0.0
Inventories, net	0.0	0.0
Loan to related party	0.0
Other current assets	0.0	0.0
Total current assets	0.0	0.0
Equity investments	20.3	(19.0)
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Deferred tax assets	0.0	0.0
Affiliated loan receivables	0.0	0.7
Other assets	0.0	(0.2)
Total assets	20.3	(18.5)
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	0.0	0.0
Affiliated payables	0.0	0.0
Accrued liabilities	0.0	0.0
Current maturities of long-term debt	0.0	0.0
Total current liabilities	0.0	0.0
Long-term debt	0.0	0.0
Affiliated debt	0.0	0.0
Other long-term liabilities	0.0	0.0
Total liabilities	0.0	0.0
Koppers shareholders’ equity (deficit)	20.3	(18.5)
Noncontrolling interests	0.0	0.0
Total liabilities and equity (deficit)	20.3	(18.5)
Koppers Inc. [Member] \| Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0.0	0.1	0.1	0.0
Receivables, net	59.2	60.4
Affiliated receivables	8.8	14.3
Inventories, net	101.4	111.9
Loan to related party	0.0
Other current assets	5.9	3.7
Total current assets	175.3	190.4
Equity investments	770.8	703.2
Property, plant and equipment, net	119.4	117.5
Goodwill	0.8	0.8
Intangible assets, net	8.0	8.7
Deferred tax assets	29.8	29.8
Affiliated loan receivables	41.8	29.6
Other assets	5.8	4.5
Total assets	1,151.7	1,084.5
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	62.5	73.8
Affiliated payables	20.8	16.6
Accrued liabilities	42.9	35.6
Current maturities of long-term debt	30.2	30.2
Total current liabilities	156.4	156.2
Long-term debt	608.5	647.5
Affiliated debt	283.5	217.5
Other long-term liabilities	83.3	81.6
Total liabilities	1,131.7	1,102.8
Koppers shareholders’ equity (deficit)	20.0	(18.3)
Noncontrolling interests	0.0	0.0
Total liabilities and equity (deficit)	1,151.7	1,084.5
Domestic Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0.0	0.7	0.4	0.9
Receivables, net	34.2	23.7
Affiliated receivables	9.1	15.2
Inventories, net	24.1	24.9
Loan to related party	0.0
Other current assets	3.4	1.9
Total current assets	70.8	66.4
Equity investments	192.7	165.7
Property, plant and equipment, net	39.0	41.2
Goodwill	153.1	153.1
Intangible assets, net	109.7	117.6
Deferred tax assets	(2.3)	0.8
Affiliated loan receivables	270.6	222.6
Other assets	4.5	4.9
Total assets	838.1	772.3
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	38.5	18.9
Affiliated payables	1.5	10.9
Accrued liabilities	19.7	23.4
Current maturities of long-term debt	0.0	0.0
Total current liabilities	59.7	53.2
Long-term debt	0.0	0.0
Affiliated debt	22.3	29.5
Other long-term liabilities	14.1	13.2
Total liabilities	96.1	95.9
Koppers shareholders’ equity (deficit)	742.0	676.4
Noncontrolling interests	0.0	0.0
Total liabilities and equity (deficit)	838.1	772.3
Non-Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	17.7	21.0	$ 32.5	$ 50.2
Receivables, net	78.0	75.5
Affiliated receivables	13.1	4.4
Inventories, net	91.6	91.8
Loan to related party	9.2
Other current assets	20.9	30.9
Total current assets	230.5	223.6
Equity investments	(0.1)	0.0
Property, plant and equipment, net	118.8	119.1
Goodwill	33.9	32.7
Intangible assets, net	28.8	29.8
Deferred tax assets	6.2	5.7
Affiliated loan receivables	32.7	31.7
Other assets	0.3	2.3
Total assets	451.1	444.9
LIABILITIES AND EQUITY (DEFICIT)
Accounts payable	40.9	48.1
Affiliated payables	17.2	15.3
Accrued liabilities	39.8	40.8
Current maturities of long-term debt	9.3	9.7
Total current liabilities	107.2	113.9
Long-term debt	33.5	34.9
Affiliated debt	39.3	36.9
Other long-term liabilities	53.0	67.6
Total liabilities	233.0	253.3
Koppers shareholders’ equity (deficit)	213.7	185.5
Noncontrolling interests	4.4	6.1
Total liabilities and equity (deficit)	$ 451.1	$ 444.9

Subsidiary Guarantor Information for Koppers Inc. Senior Notes - Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	$ 82.5	$ 95.1
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	(32.2)	(41.7)
Repayments (loans to) from affiliates	0.0	0.0
Net cash (used in) provided by divestitures and asset sales	(4.5)	14.7
Net cash used in investing activities	(36.7)	(27.0)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	(43.4)	(86.3)
Borrowings (repayments) of affiliated debt	0.0	0.0
Deferred financing costs	(1.4)	(1.0)
Dividends paid	0.0	(8.7)
Stock repurchased	0.2	(0.3)
Net cash used in financing activities	(44.6)	(96.3)
Effect of exchange rates on cash	(5.3)	10.1
Net decrease in cash and cash equivalents	(4.1)	(18.1)
Cash and cash equivalents at beginning of period	21.8	51.1
Cash and cash equivalents at end of period	17.7	33.0
Consolidation Eliminations [Member]
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	(19.9)	(9.1)
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	0.0	0.0
Repayments (loans to) from affiliates	61.2	47.5
Net cash (used in) provided by divestitures and asset sales	0.0	0.0
Net cash used in investing activities	61.2	47.5
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	0.0	0.0
Borrowings (repayments) of affiliated debt	(61.2)	(47.5)
Deferred financing costs	0.0	0.0
Dividends paid	19.9	9.1
Stock repurchased	0.0	0.0
Net cash used in financing activities	(41.3)	(38.4)
Effect of exchange rates on cash	0.0	0.0
Net decrease in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
Parent [Member] \| Reportable Legal Entities [Member]
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	(0.2)	5.4
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	0.0	0.0
Repayments (loans to) from affiliates	0.0	0.0
Net cash (used in) provided by divestitures and asset sales	0.0	0.0
Net cash used in investing activities	0.0	0.0
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	0.0	0.0
Borrowings (repayments) of affiliated debt	0.0	0.0
Deferred financing costs	0.0	0.0
Dividends paid	0.0	(5.1)
Stock repurchased	0.2	(0.3)
Net cash used in financing activities	0.2	(5.4)
Effect of exchange rates on cash	0.0	0.0
Net decrease in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
Koppers Inc. [Member] \| Reportable Legal Entities [Member]
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	10.8	10.7
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	(20.0)	(32.5)
Repayments (loans to) from affiliates	(12.2)	3.8
Net cash (used in) provided by divestitures and asset sales	0.0	12.4
Net cash used in investing activities	(32.2)	(16.3)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	(42.5)	(87.8)
Borrowings (repayments) of affiliated debt	66.0	100.6
Deferred financing costs	(1.4)	(1.0)
Dividends paid	(0.8)	(6.2)
Stock repurchased	0.0	0.0
Net cash used in financing activities	21.3	5.6
Effect of exchange rates on cash	0.0	0.1
Net decrease in cash and cash equivalents	(0.1)	0.1
Cash and cash equivalents at beginning of period	0.1	0.0
Cash and cash equivalents at end of period	0.0	0.1
Domestic Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	76.1	58.2
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	(3.2)	(4.1)
Repayments (loans to) from affiliates	(48.0)	(49.9)
Net cash (used in) provided by divestitures and asset sales	0.7	2.2
Net cash used in investing activities	(50.5)	(51.8)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	0.0	0.1
Borrowings (repayments) of affiliated debt	(7.2)	(3.9)
Deferred financing costs	0.0	0.0
Dividends paid	(19.1)	(3.1)
Stock repurchased	0.0	0.0
Net cash used in financing activities	(26.3)	(6.9)
Effect of exchange rates on cash	0.0	0.0
Net decrease in cash and cash equivalents	(0.7)	(0.5)
Cash and cash equivalents at beginning of period	0.7	0.9
Cash and cash equivalents at end of period	0.0	0.4
Non-Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Subsidiary, Sale of Stock [Line Items]
Cash provided by (used in) operating activities	15.7	29.9
Cash provided by (used in) investing activities:
Capital expenditures and acquisitions	(9.0)	(5.1)
Repayments (loans to) from affiliates	(1.0)	(1.4)
Net cash (used in) provided by divestitures and asset sales	(5.2)	0.1
Net cash used in investing activities	(15.2)	(6.4)
Cash provided by (used in) financing activities:
Borrowings (repayments) of long-term debt	(0.9)	1.4
Borrowings (repayments) of affiliated debt	2.4	(49.2)
Deferred financing costs	0.0	0.0
Dividends paid	0.0	(3.4)
Stock repurchased	0.0	0.0
Net cash used in financing activities	1.5	(51.2)
Effect of exchange rates on cash	(5.3)	10.0
Net decrease in cash and cash equivalents	(3.3)	(17.7)
Cash and cash equivalents at beginning of period	21.0	50.2
Cash and cash equivalents at end of period	$ 17.7	$ 32.5