Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax amount	$ (31,100)	$ (77,982)	$ 12,623	$ (232,777)
Other Comprehensive Income (Loss), Tax, Total	7,777	19,496	(2,924)	58,195
Other comprehensive income (loss), before reclassifications, net of tax amount			4,333	(175,088)
Reclassification from accumulated other comprehensive income, current period, net of tax amount			(5,366)	(506)
Other comprehensive income (loss), net of tax amount	(23,323)	(58,486)	9,699	(174,582)
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	(19,633)	(44,529)	10,901	(200,200)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, before tax amount	3,940	(33,784)	7,799	(33,251)
Other comprehensive income (loss), before tax amount	(15,693)	(78,313)	18,700	(233,451)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	4,910	11,132	(2,494)	50,050
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(985)	8,446	(1,950)	8,313
Other Comprehensive Income (Loss), Tax, Total	3,925	19,578	(4,444)	58,363
Other comprehensive income (loss), before reclassifications, net of tax amount	(14,723)	(33,397)	8,407	(150,150)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	2,955	(25,338)	5,849	(24,938)
Other comprehensive income (loss), net of tax amount	(11,768)	(58,735)	14,256	(175,088)
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	27	27	55	55
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(7)	(6)	(14)	(14)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	20	21	41	41
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	0	0	25	0
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	0	0	(6)	0
Reclassification from accumulated other comprehensive income, current period, net of tax amount	0	0	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	69	304	146	619
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(17)	(76)	(36)	(154)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	52	228	110	465
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	96	331	226	674
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(24)	(82)	(56)	(168)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	72	249	170	506
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	(19,500)	0	(13,231)	0
Reclassification from accumulated other comprehensive income, current period, before tax amount	3,997	0	6,928	0
Other comprehensive income (loss), before tax amount	(15,503)	0	(6,303)	0
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	4,875	0	3,308	0
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(999)	0	(1,732)	0
Other Comprehensive Income (Loss), Tax, Total	3,876	0	1,576	0
Other comprehensive income (loss), before reclassifications, net of tax amount	(14,625)	0	(9,923)	0
Reclassification from accumulated other comprehensive income, current period, net of tax amount	2,998	0	5,196	0
Other comprehensive income (loss), net of tax amount	$ (11,627)	$ 0	$ (4,727)	$ 0