Fixed assets - Summary of Fixed Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Fixed assets	$ 2,522	$ 2,523
Less: accumulated depreciation and amortization	(2,503)	(2,445)
Fixed assets, net	19	78
Furniture and fixtures [Member]
Property Plant And Equipment [Line Items]
Fixed assets	931	931
Computer and office equipment [Member]
Property Plant And Equipment [Line Items]
Fixed assets	1,167	1,168
Computer software [Member]
Property Plant And Equipment [Line Items]
Fixed assets	375	375
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Fixed assets	$ 49	$ 49