Accumulated Other Comprehensive Income - Unrealized gains (losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (125,589)	$ (71,025)	$ (139,974)	$ (2,426)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(15,661)	(55,605)	(1,276)	(124,204)
Ending balance	(141,250)	(126,630)	(141,250)	(126,630)
Unrealized gains and (Losses) on available- for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(114,658)	(53,240)	(128,896)	15,674
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(15,808)	(55,919)	(1,570)	(124,833)
Ending balance	(130,466)	(109,159)	(130,466)	(109,159)
Unrealized gains (losses) on securities available-for-sale without other than temporary impairment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(116,844)	(55,888)	(131,135)	13,155
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(15,827)	(55,586)	(1,536)	(124,629)
Ending balance	(132,671)	(111,474)	(132,671)	(111,474)
Unrealized gains (losses) on securities available-for-sale with other than temporary impairment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	2,186	2,648	2,239	2,519
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	19	(333)	(34)	(204)
Ending balance	2,205	2,315	2,205	2,315
Retirement plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(10,931)	(17,785)	(11,078)	(18,100)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	147	314	294	629
Ending balance	$ (10,784)	$ (17,471)	$ (10,784)	$ (17,471)