Stock-based compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Minimum
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vested and expected to vest range based on shareholder return	50.00%
Maximum
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vested and expected to vest range based on shareholder return	150.00%
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. The first part is vested ratably over five or four years commencing at the date of grant (“the graduated vesting portion”) and the second part is 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 will vest ratably 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	69,488	52,584
Restricted Stock Expense	$ 4,400	$ 4,500
Incentive award, tax benefit	300	$ 500
Fair Market Value of stock vested at vesting date	8,900
Windfall Net Of Shortfall	1,100
Restricted Stock Units (RSUs) | Executive Officers | Share Vesting On Grant Date
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Fair Market Value of stock vested at vesting date	$ 5,800
Restricted Stock Units (RSUs) | Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock granted	1,029	530	25,321
Restricted Stock Expense	$ 67	$ 44
Incentive award, tax benefit	13	$ 8
Fair Market Value of stock vested at vesting date	67
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	$ 11,400
Stock granted	57,715	56,857
Restricted Stock Expense	$ 3,600	$ 3,700
Incentive award, tax benefit	$ 100	$ 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 8 months 19 days