Accumulated Other Comprehensive Income - Unrealized gains (losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income (Loss)
Balance	$ 549,041	$ 527,976
Balance	571,945	520,766
Unrealized gains and (Losses) on available- for-sale Securities
Accumulated Other Comprehensive Income (Loss)
Balance	(127,807)	(118,000)
Current period Change	11,100	(11,096)
Balance	(116,707)	(129,096)
Unrealized gains (losses) on securities available-for-sale without other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Balance	(129,979)	(120,252)
Current period Change	11,096	(11,010)
Balance	(118,883)	(131,262)
Unrealized gains (losses) on securities available-for-sale with other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Balance	2,172	2,252
Current period Change	4	(86)
Balance	2,176	2,166
Retirement plans
Accumulated Other Comprehensive Income (Loss)
Balance	(4,478)	(9,087)
Current period Change	3	73
Balance	(4,475)	(9,014)
Accumulated Other Comprehensive Income/(Loss)
Accumulated Other Comprehensive Income (Loss)
Balance	(132,285)	(127,087)
Current period Change	11,103	(11,023)
Balance	$ (121,182)	$ (138,110)