Fair Values of Assets and Liabilities - Changes in Fair Value for Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance		$ (2,303)	$ (3,419)	$ (1,885)	$ (3,199)
Net Gains (Losses) Included in Net Income		651	(1,315)	(2,036)	(3,558)
Purchases		264	25	912	430
Sales		(9)	(9)	(14)	(28)
Principal Payments		0	0	0	0
Issuances		0	0	0	0
Settlements		585	962	2,211	2,599
End of Period Balance		(812)	(3,756)	(812)	(3,756)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period		1,438	(693)	666	(1,925)
Available-for-sale securities	[1]	81,704		81,704		$ 69,706
Available-for-sale investment securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of Period Balance					1
Purchases					0
Sales					0
Principal Payments					(1)
Issuances					0
Settlements					0
End of Period Balance			0		0
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period					0
Obligations of state and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of Period Balance					1
Purchases					0
Sales					0
Principal Payments					(1)
Issuances					0
Settlements					0
End of Period Balance			0		0
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period					0
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of Period Balance		3,326	3,633	3,377	3,755
Net Gains (Losses) Included in Net Income		(212)	134	(194)	(37)
Purchases		0	1	1	3
Sales		1	(292)	(188)	(440)
Principal Payments		0	0	0	0
Issuances		72	106	191	301
Settlements		0	0	0	0
End of Period Balance		3,187	3,582	3,187	3,582
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period		(212)	134	(194)	(37)
Mortgage Banking Revenue
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Net Gains (Losses) Included in Net Income		89	35	185	133
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period		20	11	20	11
Commercial Products Revenue
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Net Gains (Losses) Included in Net Income		563	(1,400)	(2,200)	(3,700)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period		1,400	(705)	716	$ (1,900)
Other Noninterest Income
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Net Gains (Losses) Included in Net Income		(1)	1	(70)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period		$ (1)	$ 1	$ (70)

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.