Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	$ 6,337	$ 7,061
Less: Accumulated depreciation	(4,902)	(5,935)
Property and equipment, net	1,435	1,126
Equipment
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	5,351	5,356
Software
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	364	180
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	600	896
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	$ 22	$ 629