Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	$ 10	$ 10	$ 17	$ 23
Interest on securities	444	461	1,354	1,374
Interest and fees on loans and leases	1,909	1,910	5,604	5,640
Compensation and benefits	(685)	(690)	(2,132)	(2,099)
Other noninterest expense	226	232	664	741
Income before income taxes	837	728	2,298	2,151
Applicable income tax expense	(188)	(155)	(507)	(457)
Net Income	649	573	1,791	1,694
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(60)	(108)	(187)	(300)
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	0	(11)	0	(17)
Income before income taxes	0	(11)	0	(17)
Applicable income tax expense	0	2	0	4
Net Income	0	(9)	0	(13)
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	(31)	(33)	(91)	(97)
Income before income taxes	(31)	(33)	(91)	(97)
Applicable income tax expense	6	7	19	21
Net Income	(25)	(26)	(72)	(76)
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	(43)	(91)	(149)	(270)
Income before income taxes	(43)	(91)	(149)	(270)
Applicable income tax expense	10	21	36	62
Net Income	(33)	(70)	(113)	(208)
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	(1)	(1)	(1)	(1)
Income before income taxes	(2)	(1)	(2)	(1)
Applicable income tax expense	0	0	0	0
Net Income	(2)	(1)	(2)	(1)
Reclassification out of AOCI | Other
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other noninterest expense	0	(2)	0	(2)
Income before income taxes	0	(2)	0	(2)
Applicable income tax expense	0	0	0	0
Net Income	0	(2)	0	(2)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	$ (1)	$ 0	$ (1)	$ 0