Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 366,122	$ 350,994	$ 306,771
AFS investment securities
Net unrealized gains (losses)	(250,273)	(63,714)	55,628
Unrealized (losses) on AFS securities transferred to HTM securities	(67,604)	0	0
Amortization of net unrealized losses on AFS securities transferred to HTM securities	9,870	1,551	3,359
Reclassification adjustment for net losses (gains) realized in net income	1,922	16	(9,222)
Income tax (expense) benefit	78,159	15,557	(12,429)
Other comprehensive income (loss) on investment securities AFS	(227,926)	(46,591)	37,336
Fair value adjustment on cash flow hedge	3,626	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(212)	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(54)	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	3,360	0	0
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(325)	(148)	(148)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	1,494	0
Net actuarial gain (loss)	(51,745)	25,519	7,780
Amortization of actuarial loss	658	4,594	3,897
Income tax (expense) benefit	13,495	(7,803)	(3,064)
Other comprehensive income (loss) on pension and postretirement obligations	(37,917)	23,656	8,465
Other Comprehensive Income (Loss), Net of Tax	(262,483)	(22,935)	45,801
Comprehensive income	$ 103,639	$ 328,059	$ 352,572