Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	$ 701	$ 735
Securities available for sale	45,364	27,556
Loans, net of unearned income	101,854	101,185
Netting adjustments	(284)	(380)
Total derivative assets	1,962	1,798
LIABILITIES MEASURED ON A RECURRING BASIS
Netting adjustments	(1,526)	(675)
U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	9,472	1,000
Other securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	13
Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	5,122	2,164
Mortgage-backed securities | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	9,651	10,106
Fair Value, Recurring
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	683	717
Commercial loans	18	18
Total trading account assets	701	735
Securities available for sale	45,364	27,556
Total other investments	105	81
Loans, net of unearned income	11	11
Loans held for sale	281	264
Derivative assets	2,246	2,178
Netting adjustments	(284)	(380)
Total derivative assets	1,962	1,798
Total assets on a recurring basis at fair value	48,424	30,445
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	749	910
Fair Value, Recurring | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	21,119	14,273
Fair Value, Recurring | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	530	633
Securities available for sale	9,472	1,000
Fair Value, Recurring | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	96	24
Securities available for sale	0	0
Fair Value, Recurring | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	13	13
Securities available for sale	0	13
Fair Value, Recurring | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	9,651	10,106
Fair Value, Recurring | Principal investments: Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	1	1
Fair Value, Recurring | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	46	54
Fair Value, Recurring | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	33	13
Fair Value, Recurring | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	59	27
Fair Value, Recurring | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	44	47
Fair Value, Recurring | Mortgage-backed securities | Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	5,122	2,164
Fair Value, Recurring | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	588	759
Fair Value, Recurring | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,687	826
Netting adjustments	(1,526)	(675)
Total derivative liabilities	161	151
Fair Value, Recurring | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	807	1,584
Fair Value, Recurring | Interest rate | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	253	288
Fair Value, Recurring | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	81	109
Fair Value, Recurring | Foreign exchange | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	76	103
Fair Value, Recurring | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,330	426
Fair Value, Recurring | Commodity | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,335	408
Fair Value, Recurring | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1	1
Fair Value, Recurring | Credit | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	12	11
Fair Value, Recurring | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	27	58
Fair Value, Recurring | Other | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11	16
Level 1 | Fair Value, Recurring
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Commercial loans	0	0
Total trading account assets	0	0
Securities available for sale	0	0
Total other investments	24	0
Loans, net of unearned income	0	0
Loans held for sale	0	0
Derivative assets	71	78
Netting adjustments	0	0
Total derivative assets	71	78
Total assets on a recurring basis at fair value	95	78
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	141	328
Level 1 | Fair Value, Recurring | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | Principal investments: Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 | Fair Value, Recurring | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 | Fair Value, Recurring | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	24	0
Level 1 | Fair Value, Recurring | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	24	0
Level 1 | Fair Value, Recurring | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Level 1 | Fair Value, Recurring | Mortgage-backed securities | Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 1 | Fair Value, Recurring | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	75	256
Level 1 | Fair Value, Recurring | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	66	72
Netting adjustments	0	0
Total derivative liabilities	66	72
Level 1 | Fair Value, Recurring | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 1 | Fair Value, Recurring | Interest rate | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 | Fair Value, Recurring | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	71	78
Level 1 | Fair Value, Recurring | Foreign exchange | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	66	72
Level 1 | Fair Value, Recurring | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 1 | Fair Value, Recurring | Commodity | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 | Fair Value, Recurring | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 1 | Fair Value, Recurring | Credit | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 | Fair Value, Recurring | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 1 | Fair Value, Recurring | Other | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 2 | Fair Value, Recurring
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	683	717
Commercial loans	18	18
Total trading account assets	701	735
Securities available for sale	45,364	27,543
Total other investments	0	0
Loans, net of unearned income	0	0
Loans held for sale	281	264
Derivative assets	2,136	2,009
Netting adjustments	0	0
Total derivative assets	2,136	2,009
Total assets on a recurring basis at fair value	48,482	30,551
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	2,127	1,246
Level 2 | Fair Value, Recurring | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	21,119	14,273
Level 2 | Fair Value, Recurring | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	530	633
Securities available for sale	9,472	1,000
Level 2 | Fair Value, Recurring | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	96	24
Securities available for sale	0	0
Level 2 | Fair Value, Recurring | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	13	13
Securities available for sale	0	0
Level 2 | Fair Value, Recurring | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	9,651	10,106
Level 2 | Fair Value, Recurring | Principal investments: Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 | Fair Value, Recurring | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 | Fair Value, Recurring | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 | Fair Value, Recurring | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 | Fair Value, Recurring | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	44	47
Level 2 | Fair Value, Recurring | Mortgage-backed securities | Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	5,122	2,164
Level 2 | Fair Value, Recurring | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	513	503
Level 2 | Fair Value, Recurring | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,614	743
Netting adjustments	0	0
Total derivative liabilities	1,614	743
Level 2 | Fair Value, Recurring | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	774	1,528
Level 2 | Fair Value, Recurring | Interest rate | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	253	288
Level 2 | Fair Value, Recurring | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	10	31
Level 2 | Fair Value, Recurring | Foreign exchange | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	10	31
Level 2 | Fair Value, Recurring | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,330	424
Level 2 | Fair Value, Recurring | Commodity | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,335	408
Level 2 | Fair Value, Recurring | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 2 | Fair Value, Recurring | Credit | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	5	0
Level 2 | Fair Value, Recurring | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	22	26
Level 2 | Fair Value, Recurring | Other | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11	16
Level 3 | Fair Value, Recurring
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Commercial loans	0	0
Total trading account assets	0	0
Securities available for sale	0	13
Total other investments	10	14
Loans, net of unearned income	11	11
Loans held for sale	0	0
Derivative assets	39	91
Netting adjustments	0	0
Total derivative assets	39	91
Total assets on a recurring basis at fair value	60	129
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	7	11
Level 3 | Fair Value, Recurring | Agency residential collateralized mortgage obligations
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 3 | Fair Value, Recurring | U.S. Treasury, agencies and corporations
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 3 | Fair Value, Recurring | States and political subdivisions
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 3 | Fair Value, Recurring | Other securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	13
Level 3 | Fair Value, Recurring | Agency commercial mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 3 | Fair Value, Recurring | Principal investments: Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	1	1
Level 3 | Fair Value, Recurring | Principal Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	1	1
Level 3 | Fair Value, Recurring | Equity Investments, Direct
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	9	13
Level 3 | Fair Value, Recurring | Equity Investments
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	9	13
Level 3 | Fair Value, Recurring | Mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Level 3 | Fair Value, Recurring | Mortgage-backed securities | Agency residential mortgage-backed securities
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 3 | Fair Value, Recurring | Short positions
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	0	0
Level 3 | Fair Value, Recurring | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	7	11
Netting adjustments	0	0
Total derivative liabilities	7	11
Level 3 | Fair Value, Recurring | Interest rate
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	33	56
Level 3 | Fair Value, Recurring | Interest rate | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 | Fair Value, Recurring | Foreign exchange
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
Level 3 | Fair Value, Recurring | Foreign exchange | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 | Fair Value, Recurring | Commodity
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	2
Level 3 | Fair Value, Recurring | Commodity | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 | Fair Value, Recurring | Credit
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1	1
Level 3 | Fair Value, Recurring | Credit | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	7	11
Level 3 | Fair Value, Recurring | Other
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	5	32
Level 3 | Fair Value, Recurring | Other | Long positions
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Measured at NAV | Fair Value, Recurring | Principal investments: Indirect | Variable Interest Entity, Not Primary Beneficiary
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	45	53
Measured at NAV | Fair Value, Recurring | Equity Investments, Direct, NAV
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	21	7
Measured at NAV | Fair Value, Recurring | Equity Investments, Indirect, NAV
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	$ 5	$ 7