SEC Filing Details Document Details Form 8-K/A Filing Date Mar 18, 2026 Document Date Jan 5, 2026 Form Description Amendment to a previously filed 8-K Filing Group Current Reports 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.LAB - XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT EX-101.PRE - XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT XML - XBRL INSTANCE DOCUMENT