Accumulated other comprehensive income table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (163,084)	$ 2,183	$ 40,695
Total other comprehensive income (loss)	48,257	(165,267)	(38,512)
Ending Balance	(114,827)	(163,084)	2,183
Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(128,657)	(9,667)	13,255
Total other comprehensive income (loss)	32,426	(118,990)	(22,922)
Ending Balance	(96,231)	(128,657)	(9,667)
Unrealized Gain (Loss) on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(36,630)	14,137	33,276
Total other comprehensive income (loss)	16,055	(50,767)	(19,139)
Ending Balance	(20,575)	(36,630)	14,137
Defined Benefit Postretirement Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	2,203	(2,287)	(5,836)
Total other comprehensive income (loss)	(224)	4,490	3,549
Ending Balance	1,979	2,203	(2,287)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Total other comprehensive income (loss)	$ 48,257	$ (165,267)	$ (38,512)