Segment Information (Schedule Of Revenues By Geographic Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 851,307	$ 1,425,369	$ 1,478,857
Long-lived assets	542,090	664,949
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	523,099	1,038,870	1,137,070
Long-lived assets	387,097	489,189
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	328,208	386,499	$ 341,787
Long-lived assets	$ 154,993	$ 175,760