Stock-based compensation - Additional Information (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Dec. 31, 2025 |
|
| 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. | ||
| Executive Officers | Restricted Stock Units (RSUs) | |||
| Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] | |||
| Stock granted | 42,395 | 72,619 | |
| Restricted Stock Expense (Benefit) | $ 5,900 | $ 7,500 | |
| Incentive award, tax benefit (expense) | 600 | $ 600 | |
| Fair value of stocks vested at grant date | 8,300 | ||
| Fair Market Value of stock vested | 17,300 | ||
| Windfall Net Of Shortfall | 3,300 | ||
| Executive Officers | Performance Based Shares | |||
| 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 | $ 13,500 | ||
| Stock granted | 35,820 | 47,494 | |
| Restricted Stock Expense (Benefit) | $ 3,900 | $ 3,400 | |
| Incentive award, tax benefit (expense) | $ 200 | $ 400 | |
| 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. | ||
| Executive Officers | Performance Based Shares | 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 6 months 21 days | ||
| Directors | |||
| Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] | |||
| Stock granted | 1,166 | 24,476 | |
| Directors | Restricted Stock Units (RSUs) | |||
| Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] | |||
| Stock granted | 1,166 | 1,546 | |
| Restricted Stock Expense (Benefit) | $ 600 | $ 300 | |
| Incentive award, tax benefit (expense) | 100 | $ 48 | |
| Fair Market Value of stock vested | $ 100 | ||