Quarterly Data (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Selected Quarterly Financial Data [Line Items]
Restructuring and impairment charges	$ 3,100	$ 2,100	$ 4,100	$ 1,700	$ 2,300	$ 1,500	$ 2,100	$ 1,200	$ 10,955	$ 7,116	$ 8,523
Mark-to-market net losses (gains)	(13,300)				$ 16,500
Tile Coatings [Member]
Selected Quarterly Financial Data [Line Items]
Restructuring and impairment charges	$ 33,500