Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax amount	$ 43,723	$ (154,795)
Other comprehensive income (loss), tax (expense) benefit	(10,701)	38,699
Other comprehensive income (loss), before reclassifications, net of tax amount	30,726	(116,353)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	2,296	257
Other comprehensive income (loss), net of tax amount	33,022	(116,096)
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	30,534	(155,671)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, before tax amount	3,859	533
Other comprehensive income (loss), before tax amount	34,393	(155,138)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(7,404)	38,918
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(965)	(133)
Other comprehensive income (loss), tax (expense) benefit	(8,369)	38,785
Other comprehensive income (loss), before reclassifications, net of tax amount	23,130	(116,753)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	2,894	400
Other comprehensive income (loss), net of tax amount	26,024	(116,353)
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	28	28
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(7)	(8)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	21	20
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	25	0
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(6)	0
Reclassification from accumulated other comprehensive income, current period, net of tax amount	19	0
Change in Net Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax amount	77	315
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(19)	(78)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	58	237
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	130	343
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(32)	(86)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	98	257
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	6,269	0
Reclassification from accumulated other comprehensive income, current period, before tax amount	2,931	0
Other comprehensive income (loss), before tax amount	9,200	0
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(1,567)	0
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(733)	0
Other comprehensive income (loss), tax (expense) benefit	(2,300)	0
Other comprehensive income (loss), before reclassifications, net of tax amount	4,702	0
Reclassification from accumulated other comprehensive income, current period, net of tax amount	2,198	0
Other comprehensive income (loss), net of tax amount	$ 6,900	$ 0