Accumulated Other Comprehensive Income - Unrealized gains (losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss)
Balance	$ 587,668	$ 530,670	$ 549,041	$ 527,976
Balance	622,218	565,951	622,218	565,951
Unrealized gains and (Losses) on available- for-sale Securities
Accumulated Other Comprehensive Income (Loss)
Balance	(113,761)	(125,561)	(127,807)	(118,000)
Current period Change	19,596	31,628	33,642	24,067
Balance	(94,165)	(93,933)	(94,165)	(93,933)
Unrealized gains (losses) on securities available-for-sale without other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Balance	(115,942)	(127,730)	(129,979)	(120,252)
Current period Change	19,645	31,640	33,682	24,162
Balance	(96,297)	(96,090)	(96,297)	(96,090)
Unrealized gains (losses) on securities available-for-sale with other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Balance	2,181	2,169	2,172	2,252
Current period Change	(49)	(12)	(40)	(95)
Balance	2,132	2,157	2,132	2,157
Retirement plans
Accumulated Other Comprehensive Income (Loss)
Balance	(4,473)	(8,940)	(4,478)	(9,087)
Current period Change	3	73	8	220
Balance	(4,470)	(8,867)	(4,470)	(8,867)
Accumulated Other Comprehensive Income/(Loss)
Accumulated Other Comprehensive Income (Loss)
Balance	(118,234)	(134,501)	(132,285)	(127,087)
Current period Change	19,599	31,701	33,650	24,287
Balance	$ (98,635)	$ (102,800)	$ (98,635)	$ (102,800)