Other Comprehensive Income (Loss) - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balances	$ 663,558	$ 558,393
Other Comprehensive Income (Loss) Before Reclassification	(19,867)	32,948
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(28)	(2)
Total Other Comprehensive Income (Loss)	(19,895)	32,946
Ending Balances	655,254	605,331
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balances	(217,060)	(263,438)
Total Other Comprehensive Income (Loss)	(19,895)	32,946
Ending Balances	(236,955)	(230,492)
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balances	(216,546)	(262,924)
Other Comprehensive Income (Loss) Before Reclassification	(19,867)	32,948
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(28)	(2)
Total Other Comprehensive Income (Loss)	(19,895)	32,946
Ending Balances	(236,441)	(229,978)
Postretirement Benefit Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balances	(514)	(514)
Other Comprehensive Income (Loss) Before Reclassification	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0	0
Total Other Comprehensive Income (Loss)	0	0
Ending Balances	$ (514)	$ (514)