Stock-Based Compensation and Employee Benefit Plan - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Outstanding Options/RSUs, Number of Shares
Outstanding (in shares)	14,558,420
Added to plan (in shares)	0
Granted (in shares)	1,433,064
Exercised (in shares)	(336,572)
Cancelled (in shares)	(687,050)
Outstanding (in shares)	14,967,862	14,558,420
Outstanding Options Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 25.93
Granted (in dollars per share)	11.19
Exercised (in dollars per share)	4.28
Cancelled (in dollars per share)	24.82
Outstanding (in dollars per share)	$ 25.06	$ 25.93
Outstanding, remaining contractual life	6 years 3 months 11 days	6 years 9 months 11 days
Outstanding, aggregate intrinsic value	$ 0	$ 3,084
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Vested and expected to vest (in shares)	14,632,346
Exercisable (in shares)	9,238,860
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 25.23
Exercisable, weighted average exercise price (in dollars per share)	$ 28.75
Vested and expected to vest, remaining contractual life	6 years 2 months 19 days
Exercisable, remaining contractual life	4 years 9 months 7 days
Vested and expected to vest, aggregate intrinsic value	$ 0
Exercisable, aggregate intrinsic value	$ 0