Stockholders' Equity - Stock Options Activity and Status (Details) - Stock Options $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) $ / shares shares
Number of Options
Outstanding at the beginning of the period (in shares) | shares	4,459,291
Granted (in shares) | shares	1,906,683
Exercised (in shares) | shares	(334,065)	(81,105)
Forfeited/canceled (in shares) | shares	(38,069)
Outstanding at the end of the period (in shares) | shares	5,993,840
Exercisable at the end of the period (in shares) | shares	3,154,307
Unvested at the end of the period (in shares) | shares	2,839,533
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 104.97
Granted (in dollars per share) | $ / shares	146.15
Exercised (in dollars per share) | $ / shares	98.69
Forfeited/canceled (in dollars per share) | $ / shares	129.57
Outstanding at the end of the period (in dollars per share) | $ / shares	118.26
Exercisable at the end of period (in dollars per share) | $ / shares	101.23
Unvested at the end of period (in dollars per share) | $ / shares	$ 137.19
Weighted Average Remaining Contractual Term (Years)
Outstanding at the end of the period	7 years 8 months 12 days
Exercisable at the end of the period	6 years
Unvested at the end of the period	9 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars) | $	$ 129.5
Exercisable at the end of the period (in dollars) | $	113.9
Unvested at the end of period (in dollars) | $	$ 15.6
Weighted average fair value of a stock option (in dollars per share) | $ / shares	$ 56.28	$ 42.84
Aggregate grant date fair value | $	$ 107.3	$ 62.8
Total fair value of employee stock options that vested | $	$ 11.0
Stock options vested (in shares) | shares		0