Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 20,781	$ 15,166
Less accumulated depreciation and amortization		(10,009)	(7,392)
Property and equipment, net		10,772	7,774
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 2,326	2,041
Property and equipment, useful life in years		5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 6,483	4,944
Property and equipment, useful life in years	[1]	9 years
Systems Hardware
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 811	807
Property and equipment, useful life in years		5 years
Office Computers
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 8,984	6,547
Property and equipment, useful life in years		3 years
Computer and System Software
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 2,177	$ 827
Property and equipment, useful life in years		3 years

[1] Lesser of the lease term or the estimated useful lives of the improvements, which may be up to 9 years.