Stock-Based Compensation and Employee Benefit Plan - Stock Option and Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Outstanding Options/RSUs, Number of Shares
Outstanding (in shares)	11,604,403	10,504,750
Granted (in shares)	4,202,284	2,146,113
Exercised (in shares)	(398,704)	(123,153)
Cancelled (in shares)	(849,563)	(923,307)
Outstanding (in shares)	14,558,420	11,604,403	10,504,750
Outstanding Options Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 26.42	$ 23.85
Granted (in dollars per share)	19.79	30.96
Exercised (in dollars per share)	3.98	3.51
Cancelled (in dollars per share)	12.51	10.78
Outstanding (in dollars per share)	$ 25.93	$ 26.42	$ 23.85
Outstanding, remaining contractual life	6 years 9 months 11 days	6 years 4 days	6 years 1 month 10 days
Outstanding, aggregate intrinsic value	$ 3,084	$ 52,682	$ 74,717
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Vested and expected to vest (in shares)	14,133,451
Exercisable (in shares)	8,282,247
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 26.09
Exercisable, weighted average exercise price (in dollars per share)	$ 27.72
Vested and expected to vest, remaining contractual life	6 years 8 months 7 days
Exercisable, remaining contractual life	5 years 1 month 2 days
Vested and expected to vest, aggregate intrinsic value	$ 3,084
Exercisable, aggregate intrinsic value	$ 3,084