Other comprehensive (loss) income - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2024	Dec. 31, 2023
Other comprehensive (loss) income
Net unrealized loss on investment securities available for sale	$ (53,949)	$ (51,527)
Income tax benefit	(11,800)	(11,270)
Net of income taxes	(42,149)	(40,257)
Benefit plan adjustments	(4,370)	(4,370)
Income tax benefit	(956)	(956)
Net of income taxes	(3,414)	(3,414)
Derivative adjustments	368	(871)
Income tax expense (benefit)	80	(191)
Net of income taxes	288	(680)
Accumulated other comprehensive loss	$ (45,275)	$ (44,351)

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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