Income Taxes (Provision for Income Taxes) (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
U.S. Federal:
Current									$ (50,333)	$ 31,691	$ 76,117
Deferred									56,715	(49,812)	(1,979)
U.S. Federal: Total									6,382	(18,121)	74,138
U.S. State and Local:
Current									(10,489)	(2,330)	6,377
Deferred									(911)	15,316	4,682
U.S. State and Local: Total									(11,400)	12,986	11,059
International:
Current									16,224	(3,418)	21,014
Deferred									1,177	9,106	764
International: Total									17,401	5,688	21,778
Total current									(44,598)	25,943	103,508
Total deferred									56,981	(25,390)	3,467
Total provision for income taxes	$ (8,362)	$ (1,976)	$ 6,458	$ 16,263	$ (38,147)	$ 10,828	$ 790	$ 27,082	$ 12,383	$ 553	$ 106,975
Effective tax rate									5.80%	0.20%	53.00%