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, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax amount	$ 73,931	$ (323,790)	$ (42,013)
Other Comprehensive Income (Loss), Tax, Total	(18,251)	80,947	10,504
Other comprehensive income (loss), before reclassifications, net of tax amount	43,185	(244,088)	(32,971)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	12,495	1,245	1,462
Other comprehensive income (loss), net of tax amount	55,680	(242,843)	(31,509)
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	50,537	(229,524)	(49,454)
Reclassification from accumulated other comprehensive income net current period before tax	(39)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, before tax amount	15,557	(86,033)	2,647
Other comprehensive income (loss), before tax amount	66,055	(315,557)	(46,807)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(12,404)	57,381	12,364
Reclassification from Aoci net current period tax	10
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(3,889)	21,508	(662)
Other Comprehensive Income (Loss), Tax, Total	(16,283)	78,889	11,702
Other comprehensive income (loss), before reclassifications, net of tax amount	38,133	(172,143)	(37,090)
Reclassification from accumulated other comprehensive income net current period net of tax	(29)
Other comprehensive income (loss), change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	11,668	(64,525)	1,985
Other comprehensive income (loss), net of tax amount	49,772	(236,668)	(35,105)
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	111	111
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(28)	(28)	(27)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	83	83	84
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		183
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(6)		(46)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	19		137
Change in Net Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	(691)	(10,792)	2,845
Reclassification from accumulated other comprehensive income, current period, before tax amount	177	1,089	1,655
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	173	(2,698)	(711)
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(44)	(272)	(414)
Other comprehensive income (loss), before reclassifications, net of tax amount	(518)	8,094	2,134
Reclassification from accumulated other comprehensive income, current period, net of tax amount	133	817	1,241
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	(378)	11,992	4,794
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	95	(2,998)	(1,198)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	(283)	8,994	$ 3,596
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax amount	(8,131)	(20,685)
Reclassification from accumulated other comprehensive income, current period, before tax amount	16,385	460
Other comprehensive income (loss), before tax amount	8,254	(20,225)
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	2,033	5,171
Reclassification from accumulated other comprehensive income, current period, tax (expense) benefit	(4,096)	(115)
Other Comprehensive Income (Loss), Tax, Total	(2,063)	5,056
Other comprehensive income (loss), before reclassifications, net of tax amount	(6,098)	(15,514)
Reclassification from accumulated other comprehensive income, current period, net of tax amount	12,289	345
Other comprehensive income (loss), net of tax amount	$ 6,191	$ (15,169)