Segment Information (Schedule Of Revenue From Unaffiliated Customers By Product And Service) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total revenue	$ 164,570	$ 629,094	$ 687,660	$ 646,069
Products
Total revenue		215,519	259,124	222,750
Materials
Total revenue		169,058	170,091	168,846
Services
Total revenue		$ 244,517	$ 258,445	$ 254,473