Commitments and contingencies Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 4,704,239	$ 4,632,105
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	21,626	21,427
Deferred standby letter of credit fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	190	155
Obligation to Repurchase Receivables Sold [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 150,625	$ 153,850