Accumulated Other Comprehensive Income - Unrealized gains (losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ (138,110)	$ (125,589)	$ (127,087)	$ (139,974)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3,609	(15,661)	(7,414)	(1,276)
Ending balance	(134,501)	(141,250)	(134,501)	(141,250)
Unrealized gains and (Losses) on available- for-sale Securities
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(129,096)	(114,658)	(118,000)	(128,896)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3,535	(15,808)	(7,561)	(1,570)
Ending balance	(125,561)	(130,466)	(125,561)	(130,466)
Unrealized gains (losses) on securities available-for-sale without other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(131,262)	(116,844)	(120,252)	(131,135)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3,532	(15,827)	(7,478)	(1,536)
Ending balance	(127,730)	(132,671)	(127,730)	(132,671)
Unrealized gains (losses) on securities available-for-sale with other than temporary impairment
Accumulated Other Comprehensive Income (Loss)
Beginning balance	2,166	2,186	2,252	2,239
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3	19	(83)	(34)
Ending balance	2,169	2,205	2,169	2,205
Retirement plans
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(9,014)	(10,931)	(9,087)	(11,078)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	74	147	147	294
Ending balance	$ (8,940)	$ (10,784)	$ (8,940)	$ (10,784)