Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax amount	$ 83,349	$ (29,576)	$ 254,237	$ (16,953)
Other Comprehensive Income (Loss), Tax, Total	(20,837)	7,392	(63,559)	4,468
Other comprehensive income (loss), before reclassifications, net of tax amount			42,444	(21,394)
Reclassification from accumulated other comprehensive income, current period, net of tax amount			148,234	8,909
Other comprehensive income (loss), net of tax amount	62,512	(22,184)	190,678	(12,485)
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	55,892	(26,963)	47,579	(16,062)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, before tax amount	3,688	4,000	11,020	11,799
Reclassification from accumulated other comprehensive income, current period, before tax amount	0	0	182,792	0
Other comprehensive income (loss), before tax amount	59,580	(22,963)	241,391	(4,263)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(13,973)	6,740	(11,895)	4,246
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	0	0	(45,698)	0
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(922)	(1,000)	(2,755)	(2,950)
Other Comprehensive Income (Loss), Tax, Total	(14,895)	5,740	(60,348)	1,296
Other comprehensive income (loss), before reclassifications, net of tax amount	41,919	(20,223)	35,684	(11,816)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	0	0	137,094	0
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	2,766	3,000	8,265	8,849
Other comprehensive income (loss), net of tax amount	44,685	(17,223)	181,043	(2,967)
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	83	83
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(7)	(7)	(21)	(21)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	21	21	62	62
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	(13)	25
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	0	0	3	(6)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	0	0	(10)	19
Change in Net Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax amount	84	70	263	216
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(21)	(18)	(65)	(54)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	63	52	198	162
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	112	98	333	324
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(28)	(25)	(83)	(81)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	84	73	250	243
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	18,826	(11,338)	(2,007)	(24,569)
Reclassification from accumulated other comprehensive income, current period, before tax amount	4,831	4,627	14,520	11,555
Other comprehensive income (loss), before tax amount	23,657	(6,711)	12,513	(13,014)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(4,706)	2,834	502	6,142
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(1,208)	(1,157)	(3,630)	(2,889)
Other Comprehensive Income (Loss), Tax, Total	(5,914)	1,677	(3,128)	3,253
Other comprehensive income (loss), before reclassifications, net of tax amount	14,120	(8,504)	(1,505)	(18,427)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	3,623	3,470	10,890	8,666
Other comprehensive income (loss), net of tax amount	$ 17,743	$ (5,034)	$ 9,385	$ (9,761)