Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Federal and state operating loss carryforwards	$ 172,530	$ 154,912
Equity compensation	21,454	17,217
R&D tax credits, net of reserves	23,452	0
Other	10,361	2,089
Total deferred tax assets	227,797	174,218
Deferred tax liabilities:
Convertible debt	(24,795)	0
Other	(159)	0
Total deferred tax liabilities	(24,954)	0
Valuation allowance	(202,843)	(174,218)
Net deferred tax assets	$ 0	$ 0