Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	$ (7)	$ (38)	$ 3	$ (84)
Interest and fees on loans and leases	1,899	1,315	5,445	3,377
Compensation and benefits	(629)	(605)	(2,036)	(1,900)
Income (loss) before income taxes	846	845	2,338	2,179
Applicable income tax expense	(186)	(192)	(519)	(470)
Net income	660	653	1,819	1,709
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income	(72)	2	(187)	107
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	0	0	(1)	3
Income (loss) before income taxes	0	0	(1)	3
Applicable income tax expense	0	0	0	(1)
Net income	0	0	(1)	2
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	(94)	4	(240)	140
Income (loss) before income taxes	(94)	4	(240)	140
Applicable income tax expense	22	(1)	55	(31)
Net income	(72)	3	(185)	109
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income (loss) before income taxes	0	(1)	(1)	(5)
Applicable income tax expense	0	0	0	1
Net income	0	(1)	(1)	(4)
Reclassification out of AOCI | Amortization of net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	0	(1)	(2)	(3)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	$ 0	$ 0	$ 0	$ (2)