Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Federal and State net operating loss carryforward	$ 325,655	$ 293,736
Foreign net operating loss carryforward	8,620	13,520
Research tax credits	35,065	37,066
Lease liability	39,548	2,164
Deferred revenue	60,657	973
Non-cash stock-based compensation	22,577	13,679
Original discount interest	3,177	4,326
Other	12,019	2,820
Total deferred tax assets	507,318	368,284
Valuation allowance	(504,788)	(365,772)
Net deferred tax assets	2,530	2,512
Deferred tax liabilities:
ROU assets	(1,253)	(1,033)
Intangibles	(1,198)	(1,279)
Other	(79)	(200)
Total deferred tax liabilities	(2,530)	(2,512)
Net deferred tax assets	$ 0	$ 0