Stock-based compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock granted	1,546		25,462
Restricted Stock Units (RSUs)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock-Based Compensation, vesting rights	Unless otherwise stated in an agreement, the compensation cost associated with the shares of restricted stock granted prior to 2021 was determined based on a two-prong vesting schedule. These grants include ratable vesting over five or four years commencing at the date of grant (the “graduated vesting portion”) with a portion vested at termination of employment after attainment of 55 years of age and 10 years of service or 60 years of age and 5 years of service (“the retirement vesting portion”). The graduated vesting portion is accelerated at termination of employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service. Restricted stock granted on or after 2021 have ratable vesting in equal annual installments over a period of 4 years or 3 years, depending on the classification of the employee. The vesting schedule is accelerated at termination of employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service.
Restricted Stock Units (RSUs) | Executive Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock granted	72,619	77,859
Restricted Stock Expense (Benefit)	$ 7,500	$ 6,400
Incentive award, tax benefit (expense)	600	$ 600
Fair value of stocks vested at grant date	8,700
Fair Market Value of stock vested	11,700
Windfall Net Of Shortfall	$ 1,100
Restricted Stock Units (RSUs) | Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock granted	1,546	1,195
Restricted Stock Expense (Benefit)	$ 300	$ 98
Incentive award, tax benefit (expense)	48	$ 18
Fair Market Value of stock vested	100
Performance Based Shares | Executive Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total unrecognized compensation cost related to non-vested restricted stock awards and performance shares to members of management	$ 12,900
Stock granted	47,494	65,225
Restricted Stock Expense (Benefit)	$ 3,400	$ 5,000
Incentive award, tax benefit (expense)	$ 400	$ 300
Stock-Based Compensation, vesting rights	The number of shares that will ultimately vest ranges from 50% to a 150% of target based on both market (TSR) and performance (ROATCE) conditions. The performance shares vest at the end of the three-year performance cycle. If a participant terminates employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service, the performance shares shall continue outstanding and vest at the end of the performance cycle.
Performance Based Shares | Executive Officers | Weighted Average
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total unrecognized compensation cost related to non-vested restricted stock awards and performance shares to members of management, period of recognition (in years)		1 year 7 months 24 days