Other Comprehensive Income (Loss) - Tax Effect Allocated to Each Component of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Before-Tax Amount
Other Comprehensive Income, Net unrealized losses	$ (202,310)	$ (31,619)	$ 15,222
Tax (Expense) Benefit
Other Comprehensive Income, Net unrealized losses	49,571	7,743	(3,732)
Net of Tax
Other comprehensive (loss) income	(152,739)	(23,876)	11,490
Available-for-sale securities
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications	(229,463)	(46,301)	22,381
Reclassification adjustment	11,916	(275)	(430)
Other Comprehensive Income, Net unrealized losses	(217,547)	(46,576)	21,951
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications	56,223	11,340	(5,487)
Reclassification adjustment	(2,919)	67	106
Other Comprehensive Income, Net unrealized losses	53,304	11,407	(5,381)
Net of Tax
Other comprehensive gain (loss), before reclassifications	(173,240)	(34,961)	16,894
Reclassification adjustment	8,997	(208)	(324)
Other comprehensive (loss) income	(164,243)	(35,169)	16,570
Net retirement plan actuarial (loss) gain
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications	12,761	11,785	(9,309)
Reclassification adjustment	2,260	2,951	2,366
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications	(3,127)	(2,887)	2,281
Reclassification adjustment	(554)	(723)	(580)
Net of Tax
Other comprehensive gain (loss), before reclassifications	9,634	8,898	(7,028)
Reclassification adjustment	1,706	2,228	1,786
Net retirement plan prior service credit
Before-Tax Amount
Reclassification adjustment	216	221	214
Tax (Expense) Benefit
Reclassification adjustment	(52)	(54)	(52)
Net of Tax
Reclassification adjustment	164	167	162
Employee benefit plans
Before-Tax Amount
Other Comprehensive Income, Net unrealized losses	15,237	14,957	(6,729)
Tax (Expense) Benefit
Other Comprehensive Income, Net unrealized losses	(3,733)	(3,664)	1,649
Net of Tax
Other comprehensive (loss) income	$ 11,504	$ 11,293	$ (5,080)