Fair value measurements - Fair Value Amounts of Derivative Instruments and their Effect on Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)	$ 4,684	$ (41)
Commodity contracts | Principal transactions revenue | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)	4,652	812
Other contracts | Principal transactions revenue | TBAs
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)	60	157
Other contracts | Principal transactions revenue | Purchase commitments
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)		(987)
Other contracts | Principal transactions revenue | ARS purchase commitments
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)		(1)
Other contracts | Other revenue | Foreign exchange forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income (pre-tax) Gain (Loss)	$ (28)	$ (22)