Collateralized transactions - Schedule of Disaggregation of Gross Obligation by Class of Collateral Pledged and Remaining Contractual Maturity of Repurchase Agreements and Securities Loaned Transactions (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
U.S. Government		$ 643,410
Equity securities		$ 284,987
Overnight and Open
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
U.S. Government	$ 846,269
Equity securities	247,219
Gross amount of recognized liabilities for repurchase agreements and securities loaned	$ 1,093,488