Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under U.S. GAAP Guidance (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	$ 31,703	$ 30,956
Financial instruments owned, at fair value—Foreign government debt	5,906	9,647
Financial instruments owned, at fair value—Equities	567	641
Financial instruments owned, at fair value—Corporate bonds	270
Netting and Collateral	(110,522)	(71,095)
Derivative asset total	10,968	2,879
Total	49,414	44,123
Net amounts of recognized Liabilities
Netting and Collateral	(110,522)	(71,095)
Derivative liability total	8,127	2,849
Contingent consideration	22,729	29,756
Total	30,856	32,605
Forwards
Net amounts of recognized assets
Netting and Collateral	(1)	(60)
Derivative asset total	28	392
Net amounts of recognized Liabilities
Netting and Collateral	(1)	(60)
Derivative liability total	617	419
FX swaps
Net amounts of recognized assets
Netting and Collateral	(3,148)	(538)
Derivative asset total	10,109	2,487
Net amounts of recognized Liabilities
Netting and Collateral	(3,148)	(538)
Derivative liability total	7,510	1,490
Futures
Net amounts of recognized assets
Netting and Collateral	(106,895)	(70,497)
Derivative asset total	826	0
Net amounts of recognized Liabilities
Netting and Collateral	(106,895)	(70,497)
Derivative liability total	0	940
Interest rate swaps
Net amounts of recognized assets
Netting and Collateral	(478)
Derivative asset total	5
Net amounts of recognized Liabilities
Netting and Collateral	(478)
Derivative liability total	0
FX/commodities options
Net amounts of recognized assets
Netting and Collateral		0
Derivative asset total		0
Level 1
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	31,703	30,956
Financial instruments owned, at fair value—Foreign government debt	0	0
Financial instruments owned, at fair value—Equities	567	641
Financial instruments owned, at fair value—Corporate bonds	0
Total	32,270	31,597
Net amounts of recognized Liabilities
Contingent consideration	0	0
Total	0	0
Level 1 | Forwards
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 1 | FX swaps
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 1 | Futures
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 1 | Interest rate swaps
Net amounts of recognized assets
Derivative asset	0
Net amounts of recognized Liabilities
Derivative liability	0
Level 1 | FX/commodities options
Net amounts of recognized assets
Derivative asset		0
Level 2
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	0	0
Financial instruments owned, at fair value—Foreign government debt	5,906	9,647
Financial instruments owned, at fair value—Equities	0	0
Financial instruments owned, at fair value—Corporate bonds	270
Total	127,666	83,621
Net amounts of recognized Liabilities
Contingent consideration	0	0
Total	118,649	73,944
Level 2 | Forwards
Net amounts of recognized assets
Derivative asset	29	452
Net amounts of recognized Liabilities
Derivative liability	618	479
Level 2 | FX swaps
Net amounts of recognized assets
Derivative asset	13,257	3,025
Net amounts of recognized Liabilities
Derivative liability	10,658	2,028
Level 2 | Futures
Net amounts of recognized assets
Derivative asset	107,721	70,497
Net amounts of recognized Liabilities
Derivative liability	106,895	71,437
Level 2 | Interest rate swaps
Net amounts of recognized assets
Derivative asset	483
Net amounts of recognized Liabilities
Derivative liability	478
Level 2 | FX/commodities options
Net amounts of recognized assets
Derivative asset		0
Level 3
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	0	0
Financial instruments owned, at fair value—Foreign government debt	0	0
Financial instruments owned, at fair value—Equities	0	0
Financial instruments owned, at fair value—Corporate bonds	0
Total	0	0
Net amounts of recognized Liabilities
Contingent consideration	22,729	29,756
Total	22,729	29,756
Level 3 | Forwards
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 3 | FX swaps
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 3 | Futures
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized Liabilities
Derivative liability	0	0
Level 3 | Interest rate swaps
Net amounts of recognized assets
Derivative asset	0
Net amounts of recognized Liabilities
Derivative liability	$ 0
Level 3 | FX/commodities options
Net amounts of recognized assets
Derivative asset		$ 0