Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	$ 1,171	$ 1,142
Total securities available for sale	37,298	37,185
Loans, net of unearned income (residential)	109,885	112,606
Netting adjustments	(723)	(818)
Total derivative assets	205	181
LIABILITIES MEASURED ON A RECURRING BASIS
Netting adjustments	(495)	(473)
U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	9,142	9,026
Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	3,451	3,589
Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	8,989	9,092
Level 3 | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1
Recurring
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	1,168	1,139
Commercial loans	3	3
Total trading account assets	1,171	1,142
Total securities available for sale	37,298	37,185
Total other investments	64	63
Loans, net of unearned income (residential)	9	9
Loans held for sale (residential)	73	51
Derivative assets	928	999
Netting adjustments	(723)	(818)
Total derivative assets	205	181
Total assets on a recurring basis at fair value	38,820	38,631
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,887	1,777
Netting adjustments	(495)	(473)
Total derivative liabilities	1,392	1,304
Total liabilities on a recurring basis at fair value	2,038	2,108
Recurring | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	646	804
Recurring | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	122	173
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,122	985
Recurring | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	92	89
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	74	73
Recurring | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	709	721
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	686	698
Recurring | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1	1
Recurring | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	5	16
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	4	20
Recurring | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	15,716	15,478
Recurring | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	284	340
Recurring | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	771	685
Total securities available for sale	9,142	9,026
Recurring | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	103	93
Recurring | Agency residential mortgage-backed securities | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	3,451	3,589
Recurring | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	8,989	9,092
Recurring | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	10	21
Total securities available for sale	0	0
Recurring | Principal investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	17	17
Recurring | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	2	2
Recurring | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	47	46
Recurring | Level 1
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Commercial loans	0	0
Total trading account assets	0	0
Total securities available for sale	0	0
Total other investments	0	0
Loans, net of unearned income (residential)	0	0
Loans held for sale (residential)	0	0
Derivative assets	77	74
Netting adjustments	0	0
Total derivative assets	77	74
Total assets on a recurring basis at fair value	77	74
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	60	58
Netting adjustments	0	0
Total derivative liabilities	60	58
Total liabilities on a recurring basis at fair value	81	88
Recurring | Level 1 | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	21	30
Recurring | Level 1 | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 1 | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	77	74
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	60	58
Recurring | Level 1 | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 1 | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 1 | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 1 | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 1 | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Recurring | Level 1 | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Total securities available for sale	0	0
Recurring | Level 1 | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Recurring | Level 1 | Agency residential mortgage-backed securities | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 1 | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 1 | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Total securities available for sale	0	0
Recurring | Level 1 | Principal investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 1 | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 1 | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 1 | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 2
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	1,168	1,139
Commercial loans	3	3
Total trading account assets	1,171	1,142
Total securities available for sale	37,298	37,185
Total other investments	0	0
Loans, net of unearned income (residential)	0	0
Loans held for sale (residential)	73	51
Derivative assets	850	925
Netting adjustments	0	0
Total derivative assets	850	925
Total assets on a recurring basis at fair value	39,392	39,303
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,827	1,719
Netting adjustments	0	0
Total derivative liabilities	1,827	1,719
Total liabilities on a recurring basis at fair value	2,452	2,493
Recurring | Level 2 | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	625	774
Recurring | Level 2 | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	122	175
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,122	985
Recurring | Level 2 | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	15	15
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	14	15
Recurring | Level 2 | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	709	721
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	686	698
Recurring | Level 2 | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1	1
Recurring | Level 2 | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	4	14
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	4	20
Recurring | Level 2 | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	15,716	15,478
Recurring | Level 2 | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	284	340
Recurring | Level 2 | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	771	685
Total securities available for sale	9,142	9,026
Recurring | Level 2 | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	103	93
Recurring | Level 2 | Agency residential mortgage-backed securities | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	3,451	3,589
Recurring | Level 2 | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	8,989	9,092
Recurring | Level 2 | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	10	21
Total securities available for sale	0	0
Recurring | Level 2 | Principal investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 2 | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 2 | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 2 | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 3
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Commercial loans	0	0
Total trading account assets	0	0
Total securities available for sale	0	0
Total other investments	2	2
Loans, net of unearned income (residential)	9	9
Loans held for sale (residential)	0	0
Derivative assets	1	0
Netting adjustments	0	0
Total derivative assets	1	0
Total assets on a recurring basis at fair value	12	11
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Netting adjustments	0	0
Total derivative liabilities	0	0
Total liabilities on a recurring basis at fair value	0	0
Recurring | Level 3 | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	0	0
Recurring | Level 3 | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	(2)
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 3 | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 3 | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 3 | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 3 | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets		2
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Recurring | Level 3 | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 3 | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Recurring | Level 3 | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Total securities available for sale	0	0
Recurring | Level 3 | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Recurring | Level 3 | Agency residential mortgage-backed securities | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 3 | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total securities available for sale	0	0
Recurring | Level 3 | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Total securities available for sale	0	0
Recurring | Level 3 | Principal investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 3 | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Recurring | Level 3 | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	2	2
Recurring | Level 3 | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	2	2
Recurring | Measured at NAV | Indirect investments | Variable Interest Entity, Not Primary Beneficiary
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	17	17
Recurring | Measured at NAV | Equity Investments Direct, NAV
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	41	40
Recurring | Measured at NAV | Equity Investments Indirect, NAV
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	$ 4	$ 4