Segment Information (Revenue By Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 436,315	$ 535,548	$ 903,491	$ 1,017,866
Long-lived assets	940,933		940,933		$ 1,109,126
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	345,942	447,666	721,057	855,213
Long-lived assets	756,345		756,345		903,520
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	90,373	$ 87,882	182,434	$ 162,653
Long-lived assets	$ 184,588		$ 184,588		$ 205,606