Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance		$ 2,679,800
Ending Balance	$ 3,327,361	3,327,361
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(31,040)	(47,966)
Net decrease (increase) in other comprehensive loss	5,678	22,604
Ending Balance	(25,362)	(25,362)
Change in unrealized gains on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(328)	(599)
Net decrease (increase) in other comprehensive loss	328	599
Ending Balance	0	0
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(31,368)	(48,565)
Other comprehensive income (loss) before reclassifications	6,006	23,203
Net decrease (increase) in other comprehensive loss	6,006	23,203
Ending Balance	$ (25,362)	$ (25,362)