Stock-Based Compensation and Employee Benefit Plan - Number of Shares Available for Grant (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Options/ RSUs Available for Grant
Beginning balance (in shares)	1,037,616	2,768,450
Added to plan (in shares)	40,924,861	647,159
Granted (in shares)	(18,075,790)	(2,698,594)
Exercised (in shares)	0	0
Cancelled (in shares)	1,061,054	967,760
Expired (in shares)	7,489,894	647,159
Ending Balance (in shares)	17,457,847	1,037,616