Stock-based Awards - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Outstanding at the end of the period (in shares)	24,541,512
Options to Purchase Common Stock
Number of Options
Outstanding at the beginning of period (in shares)	24,277,901
Granted (in shares)	4,812,332
Exercised (in shares)	(1,911,723)
Canceled/forfeited (in shares)	(2,636,998)
Outstanding at the end of the period (in shares)	24,541,512	24,277,901
Vested and expected to vest at the end of the period (in shares)	24,541,512
Exercisable at the end of the period (in shares)	16,700,882
Weighted-Average Exercise Price
Outstanding at the beginning of period (in dollars per share)	$ 8.12
Granted (in dollars per share)	9.56
Exercised (in dollars per share)	4.77
Canceled/forfeited (in dollars per share)	11.54
Outstanding at the end of the period (in dollars per share)	8.29	$ 8.12
Vested and expected to vest at the end of the period (in dollars per share)	8.29
Exercisable at the end of the period (in dollars per share)	$ 7.56
Weighted-Average Remaining Contractual Life
Outstanding at the end of the period	5 years 5 months 27 days	5 years 7 months 13 days
Vested and expected to vest at the end of the period	5 years 5 months 27 days
Exercisable at the end of the period	3 years 11 months 9 days
Aggregate Intrinsic Value
Intrinsic value of all outstanding options	$ 110.5
Intrinsic value of options vested and expected to vest	110.5
Intrinsic value of exercisable options	$ 86.8