Income Taxes - Summary of Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Gross deferred tax assets
Net operating loss carryforwards	$ 183,711	$ 174,369
Tax credit carryforwards	47,927	44,936
Deferred research and development expenses	59,753	63,215
Stock-based compensation	14,719	13,196
Fixed assets	1,287	1,303
Accrued expenses and other	370	325
Gross deferred tax assets	307,767	297,344
Gross deferred tax liabilities
IPR&D intangibles	(6,840)	(7,802)
Total deferred tax assets and liabilities	300,927	289,542
Valuation Allowance	(302,540)	(291,382)
Net deferred tax liability	1,613	1,840
Principal components of the deferred tax assets and liabilities
Income Tax Benefit	(227)	(1,167)
IPR&D
Principal components of the deferred tax assets and liabilities
Income Tax Benefit	$ 200	$ 1,200