Segment Information (Revenue By Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 425,717	$ 573,068	$ 1,329,208	$ 1,590,934
Long-lived assets	891,540		891,540		$ 1,109,126
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	324,559	486,912	1,045,615	1,342,125
Long-lived assets	712,661		712,661		903,520
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	101,158	$ 86,156	283,593	$ 248,809
Long-lived assets	$ 178,879		$ 178,879		$ 205,606