Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Provision for Income Taxes	$ 28,815	$ 38,980	$ 69,566	$ 79,390
Effective Income Tax Rate Reconciliation, Percent	32.00%	45.00%	28.00%	47.00%
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount			$ (23,663)
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Percent			9.00%
Increase (Decrease) in Deferred Tax Assets, Changes in Unrealized Gain (Loss) on Marketable Securities			$ (218)	$ 519
Increase (Decrease) in Deferred Tax Assets, Changes in Foreign Currency Translation Adjustments			$ (3,244)	$ 6,306