Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax amount	$ (42,013)	$ 30,068	$ 42,772
Other comprehensive income (loss), tax (expense) benefit	10,504	(7,519)	(10,693)
Other comprehensive income (loss), before reclassifications, net of tax amount	(32,971)	21,502	31,420
Reclassification from accumulated other comprehensive income, current period, net of tax amount	1,462	1,047	659
Other comprehensive income (loss), net of tax amount	(31,509)	22,549	32,079
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	(49,454)	30,622	44,136
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, before tax amount	2,647	3,177	3,605
Other comprehensive income (loss), before tax amount	(46,807)	33,799	47,741
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	12,364	(7,657)	(11,033)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(662)	(794)	(901)
Other comprehensive income (loss), tax (expense) benefit	11,702	(8,451)	(11,934)
Other comprehensive income (loss), before reclassifications, net of tax amount	(37,090)	22,965	33,103
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	1,985	2,383	2,704
Other comprehensive income (loss), net of tax amount	(35,105)	25,348	35,807
Change in Net Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	2,845	(5,128)	(5,703)
Reclassification from accumulated other comprehensive income, current period, before tax amount	1,655	1,128	(796)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(711)	1,282	1,425
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(414)	(282)	(199)
Other comprehensive income (loss), before reclassifications, net of tax amount	2,134	(3,846)	(4,278)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	1,241	846	597
Net Change in Prior Service Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax amount	111	150	250
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(27)	(38)	(63)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	84	112	187
Recognized Net Loss Due to Lump Sum Settlements [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax amount	183	119	312
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(46)	(30)	(77)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	137	89	235
Pension and Other Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax amount	4,794	(3,731)	4,345
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(1,198)	932	(1,086)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	$ 3,596	$ (2,799)	3,259
Cash Flow Hedge Derivatives {Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount			(145)
Reclassification from accumulated other comprehensive income, current period, before tax amount			(479)
Other comprehensive income (loss), before tax amount			(624)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit			36
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit			119
Other comprehensive income (loss), tax (expense) benefit			155
Other comprehensive income (loss), before reclassifications, net of tax amount			(109)
Reclassification from accumulated other comprehensive income, current period, net of tax amount			(360)
Other comprehensive income (loss), net of tax amount			$ (469)