Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 83,248	$ 96,275	$ 273,762	$ 257,360
AFS investment securities
Net unrealized (losses)	(56,924)	(100,092)	(69,512)	(268,413)
Unrealized (losses) on AFS securities transferred to HTM securities	0	0	0	(67,604)
Amortization of net unrealized losses on AFS securities transferred to HTM securities	2,327	2,888	6,883	7,269
Reclassification adjustment for net (gains) realized in net income	0	0	0	(12)
Income tax benefit	13,928	24,810	15,879	83,906
Other comprehensive (loss) on AFS securities	(40,669)	(72,394)	(46,751)	(244,854)
Cash flow hedge derivatives
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	(13,592)	0	(33,976)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	4,516	0	9,097	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	2,315	0	5,488	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(6,762)	0	(19,391)	0
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(81)	(82)	(244)	(244)
Amortization of actuarial (gain) loss	(7)	347	15	494
Income tax benefit (expense)	23	(474)	31	(470)
Other comprehensive (loss) on pension and postretirement obligations	(66)	(209)	(198)	(221)
Total other comprehensive (loss)	(47,497)	(72,603)	(66,340)	(245,074)
Comprehensive income	$ 35,751	$ 23,672	$ 207,422	$ 12,286