Income Taxes (Components of Provision for Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax provision:
Federal		$ 54,245	$ 54,315	$ 52,557
State		(7,601)	5,790	(1,576)
Foreign		88,436	60,571	26,918
Total current		135,080	120,676	77,899
Deferred tax provision:
Federal		(153,963)	(24,383)	(37,669)
State		(52,695)	(14,080)	(17,635)
Foreign		(2,030)	(8,384)	(3,351)
Total deferred		(208,688)	(46,847)	(58,655)
Provision for income taxes	$ 79,100	$ (73,608)	$ 73,829	$ 19,244