SEC Filing Details Document Details Form DEF 14A Filing Date Apr 3, 2023 Document Date Apr 3, 2023 Form Description Official notification to shareholders of matters to be brought to a vote ("Proxy") Filing Group Proxy Filings Company Koppers Holdings, Inc. Issuer Koppers Holdings Inc. Filing Formats iXBRL View HTML Download PDF Download DOC Download XLS XBRL XBRL Viewer EX-101.SCH - XBRL TAXONOMY EXTENSION SCHEMA EX-101.DEF - XBRL TAXONOMY EXTENSION DEFINITION LINKBASE EX-101.LAB - XBRL TAXONOMY EXTENSION LABEL LINKBASE EX-101.PRE - XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE XML - XBRL INSTANCE DOCUMENT