Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities (losses) gains, net	$ (9)	$ 10
Interest on securities	451	455
Interest and fees on loans and leases	1,816	1,859
Income (loss) before income taxes (FTE)(a)	653	658
Applicable income tax expense	(138)	(138)
Net Income	515	520
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(67)	(97)
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities (losses) gains, net	0	(3)
Income (loss) before income taxes (FTE)(a)	0	(3)
Applicable income tax expense	0	0
Net Income	0	(3)
Reclassification out of AOCI | Available-for-sale debt securities transferred to held-to-maturity securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on securities	(32)	(32)
Income (loss) before income taxes (FTE)(a)	(32)	(32)
Applicable income tax expense	7	7
Net Income	(25)	(25)
Reclassification out of AOCI | Cash flow hedge derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and fees on loans and leases	(56)	(89)
Income (loss) before income taxes (FTE)(a)	(56)	(89)
Applicable income tax expense	14	20
Net Income	$ (42)	$ (69)