Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 1,338,191	$ 1,093,628
Total changes in other comprehensive (loss) income	$ (37,778)	$ 1,509	(42,926)	(5,214)
Ending Balance	1,867,231	1,168,845	1,867,231	1,168,845
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			(7,862)	(2,080)
Other comprehensive loss before reclassifications			(7,253)	(5,201)
Amounts reclassified from accumulated other comprehensive loss			0	0
Total changes in other comprehensive (loss) income			(7,253)	(5,201)
Ending Balance	(15,115)	(7,281)	(15,115)	(7,281)
Unrealized Holding Gains (Losses) on Marketable Securities, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			17,521	126
Other comprehensive loss before reclassifications			(13,747)	200
Amounts reclassified from accumulated other comprehensive loss			0	0
Total changes in other comprehensive (loss) income			(13,747)	200
Ending Balance	3,774	326	3,774	326
Unrealized Gains (Losses) on Foreign Currency Forward Contracts, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			11,514	3,778
Other comprehensive loss before reclassifications			(17,215)	1,847
Amounts reclassified from accumulated other comprehensive loss			(4,711)	(2,060)
Total changes in other comprehensive (loss) income			(21,926)	(213)
Ending Balance	(10,412)	3,565	(10,412)	3,565
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			21,173	1,824
Other comprehensive loss before reclassifications			(38,215)	(3,154)
Amounts reclassified from accumulated other comprehensive loss			(4,711)	(2,060)
Total changes in other comprehensive (loss) income			(42,926)	(5,214)
Ending Balance	$ (21,753)	$ (3,390)	$ (21,753)	$ (3,390)