Other Comprehensive Income (Loss) - Tax Effect Allocated to Each Component of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Before-Tax Amount
Other Comprehensive Income, Net unrealized losses	$ (31,619)	$ 15,222	$ 25,961
Tax (Expense) Benefit
Other Comprehensive Income, Net unrealized losses	7,743	(3,732)	(6,360)
Net of Tax
Unrealized gains on HTM securities transferred to AFS securities	0	0	2,852
Other comprehensive (loss) income	(23,876)	11,490	19,601
Available-for-sale securities
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications	(46,301)	22,381	33,431
Unrealized gains on HTM securities transferred to AFS securities			3,777
Reclassification adjustment	(275)	(430)	(616)
Other Comprehensive Income, Net unrealized losses	(46,576)	21,951	36,592
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications	11,340	(5,487)	(8,190)
Unrealized gains on HTM securities transferred to AFS securities			(925)
Reclassification adjustment	67	106	151
Other Comprehensive Income, Net unrealized losses	11,407	(5,381)	(8,964)
Net of Tax
Other comprehensive gain (loss), before reclassifications	(34,961)	16,894	25,241
Unrealized gains on HTM securities transferred to AFS securities			2,852
Reclassification adjustment	(208)	(324)	(465)
Other comprehensive (loss) income	(35,169)	16,570	27,628
Net retirement plan actuarial (loss) gain
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications	11,785	(9,309)	(10,122)
Reclassification adjustment	2,951	2,366	1,677
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications	(2,887)	2,281	2,480
Reclassification adjustment	(723)	(580)	(411)
Net of Tax
Other comprehensive gain (loss), before reclassifications	8,898	(7,028)	(7,642)
Reclassification adjustment	2,228	1,786	1,266
Net actuarial gain due to curtailment
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications			(399)
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications			97
Net of Tax
Other comprehensive gain (loss), before reclassifications			(302)
Net retirement plan prior service credit
Before-Tax Amount
Other comprehensive gain (loss), before reclassifications			(1,819)
Reclassification adjustment	221	214	32
Tax (Expense) Benefit
Other comprehensive gain (loss), before reclassifications			446
Reclassification adjustment	(54)	(52)	(8)
Net of Tax
Other comprehensive gain (loss), before reclassifications			(1,373)
Reclassification adjustment	167	162	24
Employee benefit plans
Before-Tax Amount
Other Comprehensive Income, Net unrealized losses	14,957	(6,729)	(10,631)
Tax (Expense) Benefit
Other Comprehensive Income, Net unrealized losses	(3,664)	1,649	2,604
Net of Tax
Other comprehensive (loss) income	$ 11,293	$ (5,080)	$ (8,027)