Fair value measurements - Schedule of Fair Value Amounts of Derivative Instruments and their Effect on Consolidated Income Statements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income on Derivatives (pre-tax)	$ 1,162	$ 3,558	$ 4,415	$ 3,769
Commodity contracts | Principal transactions revenue, net | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income on Derivatives (pre-tax)	1,184	3,529	4,436	3,739
Other contracts | Principal transactions revenue, net | TBAs
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income on Derivatives (pre-tax)	2	36	3	38
Other contracts | Other revenue/(Compensation and related expenses) | Foreign exchange forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Recognized in Income on Derivatives (pre-tax)	$ (24)	$ (7)	$ (24)	$ (8)