Accumulated Other Comprehensive Loss - Reclassification from Each Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Reclassification Out Of Accumulated Other Comprehensive Loss
(Losses) gains on securities transactions, net	$ (1)		$ 3		$ 45	$ 52
Tax effect	(39,924)		(22,907)		(72,986)	(56,080)
Total net of tax	133,167	$ 106,058	70,424	$ 96,280	239,225	166,704
Interest and fees on loans	432,408		401,685		852,513	795,233
Amortization of actuarial net loss	32,905		30,484		65,245	59,503
Amounts Reclassified from Accumulated Other Comprehensive Loss
Reclassification Out Of Accumulated Other Comprehensive Loss
Total net of tax	133		165		263	352
Amounts Reclassified from Accumulated Other Comprehensive Loss | Unrealized gains on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Tax effect	(83)		(89)		(166)	(165)
Total net of tax	221		210		439	432
Interest and fees on loans	304		299		605	597
Amounts Reclassified from Accumulated Other Comprehensive Loss | Defined benefit pension plan
Reclassification Out Of Accumulated Other Comprehensive Loss
Tax effect	33		13		66	27
Total net of tax	(88)		(37)		(176)	(72)
Amortization of actuarial net loss	(121)		(50)		(242)	(99)
Amounts Reclassified from Accumulated Other Comprehensive Loss | Unrealized Gains and Losses on AFS Securities
Reclassification Out Of Accumulated Other Comprehensive Loss
(Losses) gains on securities transactions, net	0		(11)		0	(11)
Tax effect	0		3		0	3
Total net of tax	$ 0		$ (8)		$ 0	$ (8)