Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($) ft² Option	Dec. 31, 2019 USD ($) ft²	May 31, 2018 ft²	Sep. 30, 2021 USD ($) ft²	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) ft²	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) ft²	Jun. 01, 2023 ft²	Sep. 01, 2022 USD ($)	Dec. 31, 2020 USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset	$ 11,790			$ 11,790		$ 11,790					$ 7,568
Operating lease liabilities	12,806			12,806		12,806
Operating lease cost				500	$ 1,500	500	$ 1,500
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset	200			200		200
Operating lease liabilities	$ 200			$ 200		$ 200
Operating lease, weighted average remaining lease term	1 year 7 months			1 year 7 months		1 year 7 months
Operating lease liability, weighted average incremental borrowing rate						5.14%
5403 Lease | Santa Clara, California
Loss Contingencies [Line Items]
Area of office and laboratory space | ft²			35,000
Lease term expiration month and year			2022-08
Lease commencement date			2018-09
Letter of credit secured by restricted cash	$ 500			$ 500		$ 500
Operating lease right-of-use asset	700			700		700
Operating lease liabilities	800			800		$ 800
Operating lease, remaining lease term						11 months
5403 Lease | Santa Clara, California | Scenario Forecast
Loss Contingencies [Line Items]
Area of office and laboratory space | ft²									35,000
5353 Lease | Santa Clara, California
Loss Contingencies [Line Items]
Area of office and laboratory space | ft²		50,200						50,200
Lease commencement date								2019-12
Operating lease right-of-use asset	10,900			10,900		$ 10,900
Operating lease liabilities	$ 11,900			$ 11,900		$ 11,900
Operating lease, remaining lease term						10 years 3 months
Lease term expiration date		Aug. 31, 2022
Initial term of building		96 months						96 months
Lessee, Operating Lease, Existence of Option to Extend								true
Lease rent abatement term for first building								19 months
Lease rent abatement term for second floor								4 months
Operating lease, extended period	48 months 15 days
Operating lease extended term date	Dec. 31, 2031
Lessee, Operating Lease, Existence of Option to Extend	true
5353 Lease | Santa Clara, California | Scenario Forecast
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash										$ 1,500
5353 Lease | Santa Clara, California | Initial Security Deposit
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash		$ 1,000						$ 1,000
5403 and 5353 Lease | Santa Clara, California | Maximum
Loss Contingencies [Line Items]
Tenant improvements allowance		$ 1,800						$ 1,800
3003 Lease | Santa Clara, California
Loss Contingencies [Line Items]
Area of office and laboratory space | ft²	81,000			81,000		81,000
Lease term expiration month and year	2031-12
Initial term of building	10 years			10 years		10 years
Number of operating lease optional extension | Option	2
Operating lease, optional extension term	60 months
3003 Lease | Santa Clara, California | Initial Security Deposit
Loss Contingencies [Line Items]
Line of credit	$ 200			$ 200		$ 200
Prepayment for rent	200			200		200
3003 Lease | Santa Clara, California | Maximum
Loss Contingencies [Line Items]
Tenant improvements allowance	$ 5,500			$ 5,500		$ 5,500