Reporting For Segments (Net Sales To External Customers By Segment) (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
Segment Reporting Information [Line Items]
Net sales	$ 245,857	$ 246,291	$ 261,978	$ 264,240	$ 266,492	$ 267,739	$ 273,544	$ 274,448	$ 1,018,366	$ 1,082,223	$ 996,382
Performance Colors And Glass [Member]
Segment Reporting Information [Line Items]
Net sales									648,692	691,196	638,322
Color Solutions [Member]
Segment Reporting Information [Line Items]
Net sales									$ 369,674	$ 391,027	$ 358,060