Discontinued Operations (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net loss due to change in carrying value of discontinued operations net assets	$ 0.0	$ 0.0	$ (0.4)
Income tax benefit	$ 0.0	(3.0)	1.7
Valuation loss on pension liabilities			$ 11.8
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax benefit		(2.0)
Armstrong Flooring Inc [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net loss due to change in carrying value of discontinued operations net assets		0.0
Income tax benefit		$ (1.0)