Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under U.S. GAAP Guidance (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	$ 162,172	$ 170,381
Financial instruments owned, at fair value—Foreign government debt	16,512	14,827
Financial instruments owned, at fair value—Equities	672	989
Financial instruments owned, at fair value—Corporate bonds	374
Netting and Collateral	(46,259)	(38,289)
Net amounts presented in the statements of financial condition, assets	1,293	5,384
Total	181,023	191,581
Net amounts of recognized liabilities
Netting and Collateral	(46,259)	(38,289)
Net amounts presented in the statements of financial condition, liabilities	657	4,430
Contingent consideration	21,668	21,768
Total	22,325	26,198
FX swaps
Net amounts of recognized assets
Netting and Collateral	(90)	(1,183)
Net amounts presented in the statements of financial condition, assets	1,141	4,810
Net amounts of recognized liabilities
Netting and Collateral	(90)	(1,183)
Net amounts presented in the statements of financial condition, liabilities	454	3,679
Forwards
Net amounts of recognized assets
Netting and Collateral	(28)	(56)
Net amounts presented in the statements of financial condition, assets	96	409
Net amounts of recognized liabilities
Netting and Collateral	(28)	(56)
Net amounts presented in the statements of financial condition, liabilities	160	751
Futures
Net amounts of recognized assets
Netting and Collateral	(37,564)	(36,918)
Net amounts presented in the statements of financial condition, assets	0	165
Net amounts of recognized liabilities
Netting and Collateral	(37,564)	(36,918)
Net amounts presented in the statements of financial condition, liabilities	43	0
Interest rate swaps
Net amounts of recognized assets
Netting and Collateral	(8,577)	(132)
Net amounts presented in the statements of financial condition, assets	56	0
Net amounts of recognized liabilities
Netting and Collateral	(8,577)	(132)
Net amounts presented in the statements of financial condition, liabilities	0	0
Level 1
Net amounts of recognized assets
Financial instruments owned, at fair value—Domestic government debt	162,172	170,381
Financial instruments owned, at fair value—Foreign government debt	0	0
Financial instruments owned, at fair value—Equities	672	989
Financial instruments owned, at fair value—Corporate bonds	0
Total	200,408	208,453
Net amounts of recognized liabilities
Contingent consideration	0	0
Total	37,607	36,918
Level 1 | FX swaps
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized liabilities
Derivative liability	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 | Futures
Net amounts of recognized assets
Derivative asset	37,564	37,083
Net amounts of recognized liabilities
Derivative liability	37,607	36,918
Level 1 | Interest rate swaps
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized liabilities
Derivative liability	0	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	16,512	14,827
Financial instruments owned, at fair value—Equities	0	0
Financial instruments owned, at fair value—Corporate bonds	374
Total	26,874	21,417
Net amounts of recognized liabilities
Contingent consideration	0	0
Total	9,309	5,801
Level 2 | FX swaps
Net amounts of recognized assets
Derivative asset	1,231	5,993
Net amounts of recognized liabilities
Derivative liability	544	4,862
Level 2 | Forwards
Net amounts of recognized assets
Derivative asset	124	465
Net amounts of recognized liabilities
Derivative liability	188	807
Level 2 | Futures
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized liabilities
Derivative liability	0	0
Level 2 | Interest rate swaps
Net amounts of recognized assets
Derivative asset	8,633	132
Net amounts of recognized liabilities
Derivative liability	8,577	132
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	21,668	21,768
Total	21,668	21,768
Level 3 | FX swaps
Net amounts of recognized assets
Derivative asset	0	0
Net amounts of recognized liabilities
Derivative liability	0	0
Level 3 | Forwards
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	0
Net amounts of recognized liabilities
Derivative liability	$ 0	$ 0