Segment Information (Schedule Of Revenues By Geographic 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
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 336,072	$ 356,585	$ 367,438	$ 365,274	$ 389,447	$ 378,400	$ 356,901	$ 354,109	$ 1,425,369	$ 1,478,857	$ 1,305,529
Long-lived assets	664,949				1,109,126				664,949	1,109,126
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,038,870	1,137,070	997,713
Long-lived assets	489,189				903,520				489,189	903,520
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									386,499	341,787	$ 307,816
Long-lived assets	$ 175,760				$ 205,606				$ 175,760	$ 205,606