Stock-Based Compensation and Employee Benefit Plan - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Outstanding Options/RSUs, Number of Shares
Outstanding (in shares)	14,558,420
Granted (in shares)	981,105
Exercised (in shares)	(328,026)
Cancelled (in shares)	(298,490)
Outstanding (in shares)	14,913,009	14,558,420
Outstanding Options Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 25.93
Granted (in dollars per share)	11.44
Exercised (in dollars per share)	4.28
Cancelled (in dollars per share)	25.37
Outstanding (in dollars per share)	$ 25.47	$ 25.93
Outstanding, remaining contractual life	6 years 6 months 11 days	6 years 9 months 11 days
Outstanding, aggregate intrinsic value	$ 2,557	$ 3,084
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Vested and expected to vest (in shares)	14,541,060
Exercisable (in shares)	8,716,781
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 25.64
Exercisable, weighted average exercise price (in dollars per share)	$ 28.77
Vested and expected to vest, remaining contractual life	6 years 5 months 19 days
Exercisable, remaining contractual life	4 years 11 months 16 days
Vested and expected to vest, aggregate intrinsic value	$ 2,523
Exercisable, aggregate intrinsic value	$ 1,764