Discontinued Operations (Summary Of Cash Flow Data Related To Discontinued Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Non-cash investing activities - capital expenditures, consisting of of unpaid capital expenditure liabilities at year end	$ 3,500	$ 7,700	$ 8,400
Tile Coatings [Member] | Discontinued Operations, Held-for-sale [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Depreciation	11,264	10,778	10,080
Amortization of intangible assets	3,192	3,219	3,019
Capital expenditure	(10,126)	(5,265)	(4,656)
Non-cash operating activities - fixed asset impairment			1,243
Non-cash operating activities - goodwill impairment	42,515
Non-cash operating activities - restructuring	127		1,868
Non-cash investing activities - capital expenditures, consisting of of unpaid capital expenditure liabilities at year end	$ 1,096	$ 5,872	$ 448