Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforward	$ 294,189	$ 251,971
Research and development credits	55,789	49,683
Stock-based compensation	23,342	20,211
Lease liabilities	2,564	4,330
Other	3,953	3,777
Total gross deferred tax assets	379,837	329,972
Deferred tax liabilities:
Right-of-use lease assets	(2,420)	(4,014)
Total gross deferred tax liabilities	(2,420)	(4,014)
Valuation allowance	$ (377,417)	$ (325,958)