Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 1,338,191	$ 1,093,628
Total changes in other comprehensive income (loss)	(5,148)	(6,723)
Ending Balance	1,682,793	1,116,198
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(7,862)	(2,080)
Other comprehensive (loss) income before reclassifications	(2,001)	(1,740)
Amounts reclassified from accumulated other comprehensive loss	0	0
Total changes in other comprehensive income (loss)	(2,001)	(1,740)
Ending Balance	(9,863)	(3,820)
Unrealized Holding Gains on Marketable Securities, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	17,521	126
Other comprehensive (loss) income before reclassifications	3,534	229
Amounts reclassified from accumulated other comprehensive loss	0	0
Total changes in other comprehensive income (loss)	3,534	229
Ending Balance	21,055	355
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) income before reclassifications	(2,802)	(3,827)
Amounts reclassified from accumulated other comprehensive loss	(3,879)	(1,385)
Total changes in other comprehensive income (loss)	(6,681)	(5,212)
Ending Balance	4,833	(1,434)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	21,173	1,824
Other comprehensive (loss) income before reclassifications	(1,269)	(5,338)
Amounts reclassified from accumulated other comprehensive loss	(3,879)	(1,385)
Total changes in other comprehensive income (loss)	(5,148)	(6,723)
Ending Balance	$ 16,025	$ (4,899)