Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 3,224,370
Ending Balance	3,310,723
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(56,222)
Other comprehensive income (loss)	34,292
Ending Balance	(21,930)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(59,017)
Other comprehensive income (loss)	34,698
Ending Balance	(24,319)
Net Unrealized Gains (Losses) on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	2,795
Other comprehensive income (loss)	(406)
Ending Balance	$ 2,389