Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 87,154	$ 86,824	$ 190,514	$ 161,086
AFS investment securities
Net unrealized (losses)	(49,066)	(65,038)	(12,588)	(168,321)
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	2,289	3,273	4,556	4,381
Reclassification adjustment for net losses (gains) realized in net income	0	8	0	(12)
Income tax benefit	11,843	15,998	1,951	59,096
Other comprehensive (loss) on AFS securities	(34,934)	(45,758)	(6,081)	(172,460)
Cash flow hedge derivatives
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	(34,147)	0	(20,384)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	3,319	0	4,581	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	7,867	0	3,173	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(22,961)	0	(12,630)	0
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(81)	(81)	(163)	(163)
Amortization of actuarial loss	(7)	74	22	147
Income tax benefit (expense)	(71)	2	8	4
Other comprehensive (loss) on pension and postretirement obligations	(159)	(6)	(132)	(12)
Total other comprehensive (loss)	(58,054)	(45,764)	(18,843)	(172,472)
Comprehensive income (loss)	$ 29,100	$ 41,060	$ 171,671	$ (11,386)