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
	Mar. 31, 2024	Mar. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning of Period Balance	$ (1,885)	$ (3,199)
Net Gains (Losses) Included in Net Income	(1,683)	(316)
Purchases	378	423
Sales	(2)	(12)
Issuances	0	0
Settlements	831	839
End of Period Balance	(2,361)	(2,265)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period	(181)	529
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	44	51
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period	19	22
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	(1,700)	(365)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period	(125)	509
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	(75)	(2)
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period	(75)	(2)
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
Issuances		0
Settlements		0
End of Period Balance		1
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
Issuances		0
Settlements		0
End of Period Balance		1
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	3,377	3,755
Net Gains (Losses) Included in Net Income	30	(129)
Purchases	0	1
Sales	0	1
Issuances	55	96
Settlements	0	0
End of Period Balance	3,462	3,724
Net Change in Unrealized Gains (Losses) Relating to Assets and Liabilities Held at End of Period	$ 30	$ (129)