Operating Leases - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Leased Assets [Line Items]
Right-of-use assets	$ 5,205	$ 5,057
Operating lease liability	6,723
Operating lease cost	1,500	1,500
Cash paid included in operating lease liabilities included in cash flow from operating activities	$ 1,700	$ 1,700
South San Francisco, California
Operating Leased Assets [Line Items]
Operating lease, remaining lease term	3 years 7 months 6 days
Operating lease, discount rate	7.00%
Operating lease option to extend	true
Operating lease renewal term	2 years
South San Francisco, California | Second Amendment
Operating Leased Assets [Line Items]
Operating lease, discount rate	6.00%
South San Francisco, California | Lease Agreement | Laboratory and Office Facilities
Operating Leased Assets [Line Items]
Lease expiration date	Jul. 31, 2024
South San Francisco | Laboratory and Office Facilities | Second Amendment
Operating Leased Assets [Line Items]
Right-of-use assets	$ 1,200
Operating lease liability	$ 1,200
Operating lease commencement month and year	2020-08