Stock-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock options, Shares Subject to Options
Outstanding at the beginning of the period (in shares)	4,625,678
Granted (in shares)	21,181
Exercised (in shares)	(597,943)
Forfeited (in shares)	(128,260)
Outstanding at the end of the period (in shares)	3,920,656
Exercisable at the end of the period (in shares)	1,843,186
Exercisable and expected to vest at the end of the period (in shares)	3,781,258
Stock options, Weighted Average Option Price
Outstanding at the beginning of the period (in dollars per share)	$ 18.73
Granted (in dollars per share)	24.04
Exercised (in dollars per share)	15.48
Forfeited (in dollars per share)	19.53
Outstanding at the end of the period (in dollars per share)	19.23
Exercisable at the end of the period (in dollars per share)	16.74
Exercisable and expected to vest at the end of the period (in dollars per share)	$ 19.15
Stock options, additional information
Weighted Average Remaining Contractual Term, Outstanding	6 years 4 months 24 days
Weighted Average Remaining Contractual Term, Exercisable	4 years 10 months 24 days
Weighted Average Remaining Contractual Term, Exercisable and expected to vest	6 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding	$ 37.7
Aggregate Intrinsic Value, Exercisable	22.3
Aggregate Intrinsic Value, Exercisable and expected to vest	$ 36.7
Fair value of the Company's common stock price (in dollars per share)	$ 28.84
Weighted average fair values of options granted (in dollars per share)	$ 7.57	$ 9.77
Intrinsic value of options exercised	$ 6.7	$ 9.7