Reclassifications Out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities losses, net	$ 0	$ (1,644)
Income tax expense	(18,204)	(17,791)
Investment securities interest revenue	336,728	279,487
Long-term debt interest expense	(3,795)	(3,896)
Salaries and employee benefits expense	(84,985)	(78,698)
Other expense	(8,176)	(8,348)
Total before tax	80,835	80,091
Net of tax	62,631	62,300
Reclassifications Out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	(531)	(2,951)
Reclassifications Out of AOCI | Realized losses on AFS securities:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities losses, net	0	(1,644)
Income tax expense	0	374
Net of tax	0	(1,270)
Reclassifications Out of AOCI | Amortization of unrealized losses on HTM securities transferred from AFS:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	493	720
Investment securities interest revenue	(2,063)	(2,968)
Net of tax	(1,570)	(2,248)
Reclassifications Out of AOCI | Reclassifications related to derivative instruments accounted for as cash flow hedges:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	(368)	(210)
Long-term debt interest expense	1,440	822
Net of tax	1,072	612
Reclassifications Out of AOCI | Amortization of defined benefit pension plan net periodic pension cost components:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	11	16
Net of tax	(33)	(45)
Reclassifications Out of AOCI | Prior service cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits expense	$ (44)	$ (61)