Segment Information (Schedule Of Revenues By Geographic Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 539,331	$ 573,068	$ 535,548	$ 482,318	$ 497,043	$ 506,029	$ 470,068	$ 400,936	$ 2,130,265	$ 1,874,076	$ 1,450,047
Long-lived assets	1,109,126				1,316,944				1,109,126	1,316,944
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,788,478	1,566,260	1,080,513
Long-lived assets	903,520				1,064,823				903,520	1,064,823
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									341,787	307,816	$ 369,534
Long-lived assets	$ 205,606				$ 252,121				$ 205,606	$ 252,121