Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018			$ 3,362,469
Other comprehensive loss	$ (23,637)	$ 13,888	(20,040)	$ 24,625
Balance as of June 30, 2018	3,445,278		3,445,278
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018			(21,930)
Balance as of June 30, 2018	(41,970)		(41,970)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018			(24,319)
Other comprehensive loss			(18,275)
Balance as of June 30, 2018	(42,594)		(42,594)
Net Unrealized Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018			2,389
Other comprehensive loss			(1,765)
Balance as of June 30, 2018	$ 624		$ 624