FAIR VALUE - Schedule of Carrying Values and Estimated Fair Values for Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financial Assets
Investment in marketable equity securities	$ 78	$ 84
Investment securities available for sale	27,053	19,936
Investment securities held to maturity	10,535	9,979
Fair value of derivative financial instruments	646	640
Financial Liabilities
Fair value of derivative financial instruments	636	636
Carrying Value
Financial Assets
Cash and due from banks	764	908
Interest-earning deposits at banks	25,361	33,609
Securities purchased under agreements to resell	392	473
Investment in marketable equity securities	78	84
Investment securities available for sale	27,053	19,936
Investment securities held to maturity	10,535	9,979
Loans held for sale	86	73
Net loans	135,631	129,545
Accrued interest receivable	925	832
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	26	25
Financial Liabilities
Deposits with no stated maturity	135,920	129,427
Time deposits	15,159	16,427
Credit balances of factoring clients	1,175	1,089
Securities sold under customer repurchase agreements	386	485
Long-term borrowings	37,064	37,160
Accrued interest payable	159	137
Carrying Value | Qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Carrying Value | Non-qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	646	640
Financial Liabilities
Fair value of derivative financial instruments	636	636
Estimated Fair Value
Financial Assets
Cash and due from banks	764	908
Interest-earning deposits at banks	25,361	33,609
Securities purchased under agreements to resell	392	473
Investment in marketable equity securities	78	84
Investment securities available for sale	27,053	19,936
Investment securities held to maturity	8,946	8,503
Loans held for sale	87	73
Net loans	134,165	126,696
Accrued interest receivable	925	832
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	46	42
Financial Liabilities
Deposits with no stated maturity	135,920	129,427
Time deposits	15,151	16,416
Credit balances of factoring clients	1,175	1,089
Securities sold under customer repurchase agreements	386	485
Long-term borrowings	36,362	36,816
Accrued interest payable	159	137
Estimated Fair Value | Level 1
Financial Assets
Cash and due from banks	764	908
Interest-earning deposits at banks	25,361	33,609
Securities purchased under agreements to resell	0	0
Investment in marketable equity securities	32	36
Investment securities available for sale	0	0
Investment securities held to maturity	0	0
Loans held for sale	0	0
Net loans	0	0
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	0	0
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	0	0
Long-term borrowings	0	0
Accrued interest payable	0	0
Estimated Fair Value | Level 2
Financial Assets
Cash and due from banks	0	0
Interest-earning deposits at banks	0	0
Securities purchased under agreements to resell	392	473
Investment in marketable equity securities	46	48
Investment securities available for sale	26,892	19,779
Investment securities held to maturity	8,946	8,503
Loans held for sale	67	38
Net loans	1,412	1,479
Accrued interest receivable	925	832
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	0	0
Financial Liabilities
Deposits with no stated maturity	135,920	129,427
Time deposits	15,151	16,416
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	386	485
Long-term borrowings	36,362	36,816
Accrued interest payable	159	137
Estimated Fair Value | Level 3
Financial Assets
Cash and due from banks	0	0
Interest-earning deposits at banks	0	0
Securities purchased under agreements to resell	0	0
Investment in marketable equity securities	0	0
Investment securities available for sale	161	157
Investment securities held to maturity	0	0
Loans held for sale	20	35
Net loans	132,753	125,217
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	46	42
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	1,175	1,089
Securities sold under customer repurchase agreements	0	0
Long-term borrowings	0	0
Accrued interest payable	0	0
Estimated Fair Value | Qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Qualifying Hedges | Level 1
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Qualifying Hedges | Level 2
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Qualifying Hedges | Level 3
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Non-qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	646	640
Financial Liabilities
Fair value of derivative financial instruments	636	636
Estimated Fair Value | Non-qualifying Hedges | Level 1
Financial Assets
Fair value of derivative financial instruments	0	0
Financial Liabilities
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Non-qualifying Hedges | Level 2
Financial Assets
Fair value of derivative financial instruments	635	633
Financial Liabilities
Fair value of derivative financial instruments	635	635
Estimated Fair Value | Non-qualifying Hedges | Level 3
Financial Assets
Fair value of derivative financial instruments	11	7
Financial Liabilities
Fair value of derivative financial instruments	$ 1	$ 1