Collateralized transactions - Schedule of Gross Amounts and Offsetting Amounts of Reverse Repurchase Agreements, Repurchase Agreements, Securities Borrowed and Securities Loaned Transactions (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Reverse repurchase agreements
Gross Amounts of Recognized Assets	$ 192,898	$ 68,055
Gross Amounts Offset on the Balance Sheet	(192,898)	(68,055)
Net Amounts of Assets Presented on the Balance Sheet	0	0
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Amount	0	0
Securities Borrowed
Gross Amounts of Recognized Assets	139,852	137,177
Gross Amounts Offset on the Balance Sheet	0	0
Net Amounts of Assets Presented on the Balance Sheet	139,852	137,177
Financial Instruments	(136,622)	(130,568)
Cash Collateral Received	0	0
Net Amount	3,230	6,609
Total
Gross Amounts of Recognized Assets	332,750	205,232
Gross Amounts Offset on the Balance Sheet	(192,898)	(68,055)
Net Amounts of Assets Presented on the Balance Sheet	139,852	137,177
Financial Instruments	(136,622)	(130,568)
Cash Collateral Received	0	0
Net Amount	3,230	6,609
Repurchase agreements
Gross Amounts of Recognized Liabilities	1,046,021	999,809
Gross Amounts Offset on the Balance Sheet	(192,898)	(68,055)
Net Amounts of Liabilities Presented on the Balance Sheet	853,123	931,754
Financial Instruments	(853,123)	(931,754)
Cash Collateral Pledged	0	0
Net Amount	0	0
Securities Loaned
Gross Amounts of Recognized Liabilities	404,916	235,498
Gross Amounts Offset on the Balance Sheet	0	0
Net Amounts of Liabilities Presented on the Balance Sheet	404,916	235,498
Financial Instruments	(393,219)	(229,156)
Cash Collateral Pledged	0	0
Net Amount	11,697	6,342
Total
Gross Amounts of Recognized Liabilities	1,450,937	1,235,307
Gross Amounts Offset on the Balance Sheet	(192,898)	(68,055)
Net Amounts of Liabilities Presented on the Balance Sheet	1,258,039	1,167,252
Financial Instruments	(1,246,342)	(1,160,910)
Cash Collateral Pledged	0	0
Net Amount	$ 11,697	$ 6,342