Equity-Based Compensation - Summary of Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Summary of option activity under stock plans
Number of options outstanding, beginning balance (in shares)	33,031,298
Number of options, granted (in shares)	8,066,000
Number of options, exercised (in shares)	(24,877)
Number of options, forfeited (in shares)	(1,443,575)
Number of options, expired (in shares)	(2,258,425)
Number of options outstanding, ending balance (in shares)	37,370,421	33,031,298
Share-based Compensation Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)	$ 9.31
Weighted average exercise price, granted (in dollars per share)	2.47
Weighted average exercise price, exercised (in dollars per share)	0.66
Weighted average exercise price, forfeited (in dollars per share)	7.32
Weighted average exercise price, expired (in dollars per share)	7.74
Weighted average exercise price, ending balance (in dollars per share)	$ 8.01	$ 9.31
Weighted average remaining contractual term, outstanding	6 years	5 years 11 months 4 days
Aggregate intrinsic value, outstanding	$ 0	$ 232
Vested and expected to vest, number of options (in shares)	37,370,421
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 8.01
Weighted average expected to vest, remaining contractual term	6 years
Aggregate intrinsic value, vested and expected to vest	$ 0
Number of options exercisable (in shares)	24,448,521
Weighted average exercise price exercisable (in dollars per share)	$ 10.18
Weighted average remaining contractual term, exercisable	4 years 5 months 26 days
Exercisable, aggregate intrinsic value	$ 0