Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 96,275	$ 88,809	$ 257,360	$ 274,117
AFS investment securities
Net unrealized (losses)	(100,092)	(19,827)	(268,413)	(35,829)
Unrealized (losses) on AFS securities transferred to HTM securities	0	0	(67,604)	0
Amortization of net unrealized losses on AFS securities transferred to HTM securities	2,888	172	7,269	1,335
Reclassification adjustment for net losses (gains) realized in net income	0	0	(12)	16
Income tax benefit	24,810	4,975	83,906	8,548
Other comprehensive (loss) on AFS securities	(72,394)	(14,681)	(244,854)	(25,930)
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(82)	(37)	(244)	(111)
Amortization of actuarial loss	347	1,346	494	3,446
Income tax (expense)	(474)	(330)	(470)	(836)
Other comprehensive income (loss) on pension and postretirement obligations	(209)	979	(221)	2,498
Total other comprehensive (loss)	(72,603)	(13,702)	(245,074)	(23,431)
Comprehensive income	$ 23,672	$ 75,107	$ 12,286	$ 250,685