Commitments and Contingencies - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Right-of-use asset	$ 38,172,000		$ 38,172,000		$ 39,890,000
Operating lease liability, noncurrent	45,520,000		45,520,000		41,905,000
Operating lease cost		$ 100,000		$ 200,000
Current Headquarters
Lessee, Lease, Description [Line Items]
Minimum monthly rental expense	$ 1,900,000		$ 5,900,000
Discount rate (as a percent)	12.00%		12.00%
Right-of-use asset	$ 38,200,000		$ 38,200,000		39,900,000
Operating lease liability	45,831,000		45,831,000		$ 41,900,000
Operating lease liability, current	300,000		300,000
Operating lease liability, noncurrent	$ 45,500,000		$ 45,500,000
Building | Future Headquarters
Lessee, Lease, Description [Line Items]
Lease term	12 years		12 years
Minimum monthly rental expense			$ 600,000
Annual rent increase (as a percent)	3.00%		3.00%
Building | Current Headquarters
Lessee, Lease, Description [Line Items]
Minimum monthly rental expense			$ 24,100
Annual rent increase (as a percent)	3.00%		3.00%