Revenue Recognition (Comparison Of Geographic Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,265,052	$ 1,231,661	$ 1,214,969
U.S. [Member]
Disaggregation of Revenue [Line Items]
Total revenues	804,647	772,586	756,907
EMEA [Member]
Disaggregation of Revenue [Line Items]
Total revenues	214,204	206,975	212,699
CHINA
Disaggregation of Revenue [Line Items]
Total revenues	113,048	119,291	106,841
Other [Member]
Disaggregation of Revenue [Line Items]
Total revenues	$ 133,153	$ 132,809	$ 138,522