Stockholders' Equity - Stock Options Activity and Status (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stock option activity
Outstanding at the beginning of the period (in shares)			3,247,438
Granted (in shares)			1,625,552
Exercised (in shares)	(42,443)	(210,256)	(196,984)	(807,755)
Forfeited (in shares)			(165,492)
Outstanding at the end of the period (in shares)	4,510,514		4,510,514
Exercisable at the end of the year (in shares)	3,278,204		3,278,204
Expected to vest at the end of the year (in shares)	1,152,335		1,152,335
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)			119.33
Exercised (in dollars per share)			31.73
Forfeited (in dollars per share)			120.78
Outstanding at the end of the period (in dollars per share)	$ 104.21		104.21
Exercisable at the end of period (in dollars per share)	98.49		98.49
Expected to vest at the end of period (in dollars per share)	$ 119.30		$ 119.30
Employee stock options, Weighted Average Remaining Contractual Term
Outstanding at the end of the period			7 years 2 months 12 days
Exercisable at the end of the period			6 years 3 months 18 days
Expected to vest at the end of the period			9 years 6 months
Employee stock options, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 83.3		$ 83.3
Exercisable at the end of the period (in dollars)	81.9		81.9
Expected to vest at the end of period (in dollars)	$ 1.4		1.4
Aggregate grant date fair value			$ 19.9