Stockholders' Equity (Details 4) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stock option activity
Exercised (in shares)	(73,436)	(345,664)	(154,541)	(597,499)
Stock Options
Stock option activity
Outstanding at the beginning of the period (in shares)			3,247,438
Granted (in shares)			1,592,552
Exercised (in shares)			(154,541)
Forfeited (in shares)			(123,126)
Outstanding at the end of the period (in shares)	4,562,323		4,562,323
Exercisable at the end of the year (in shares)	3,320,647		3,320,647
Expected to vest at the end of the year (in shares)	1,160,247		1,160,247
Employee stock options, Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)			$ 93.09
Granted (in dollars per share)			119.24
Exercised (in dollars per share)			32.13
Forfeited (in dollars per share)			120.26
Outstanding at the end of the period (in dollars per share)	$ 103.55		103.55
Exercisable at the end of period (in dollars per share)	97.62		97.62
Expected to vest at the end of period (in dollars per share)	$ 119.28		$ 119.28
Employee stock options, Weighted Average Remaining Contractual Term
Outstanding at the end of the period			7 years 4 months 24 days
Exercisable at the end of the period			6 years 6 months
Expected to vest at the end of the period			9 years 8 months 12 days
Employee stock options, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 66.4		$ 66.4
Exercisable at the end of the period (in dollars)	66.1		66.1
Expected to vest at the end of period (in dollars)	$ 0.3		$ 0.3