Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	$ 10	$ 4
Interest on securities	455	439
Interest and fees on loans and leases	1,859	1,714
Income (loss) before income taxes	658	718
Applicable income tax expense	(138)	(160)
Net Income	520	558
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(97)	(50)
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	(3)	0
Income (loss) before income taxes	(3)	0
Applicable income tax expense	0	0
Net Income	(3)	0
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)	0
Income (loss) before income taxes	(32)	0
Applicable income tax expense	7	0
Net Income	(25)	0
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	(89)	(65)
Income (loss) before income taxes	(89)	(65)
Applicable income tax expense	20	15
Net Income	$ (69)	$ (50)