Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 72,838	$ 41,589
R&D credits	39,888	25,328
Deferred revenue	8,251	8,456
Deferred rent	4,219	2,966
Capitalized R&D costs	1,039	1,207
Equity compensation	1,368	883
Accrued expense and other	1,914	108
Total deferred tax assets	129,517	80,537
Deferred tax liabilities:
Depreciation	(3,726)	(2,744)
Other	(757)
Total deferred tax liabilities	(4,483)	(2,744)
Valuation allowance	$ (125,034)	$ (77,793)