FAIR VALUE - Schedule of Carrying Values and Estimated Fair Values for Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financial Assets
Investment in marketable equity securities	$ 95	$ 101
Investment securities available for sale	33,900	33,750
Investment securities held to maturity	10,324	10,239
Fair value of derivative financial instruments	553	660
Financial Liabilities
Fair value of derivative financial instruments	541	625
Carrying Value
Financial Assets
Cash and due from banks	812	814
Interest-earning deposits at banks	24,692	21,364
Securities purchased under agreements to resell	345	158
Investment in marketable equity securities	95	101
Investment securities available for sale	33,900	33,750
Investment securities held to maturity	10,324	10,239
Loans held for sale	183	82
Net loans	137,692	136,567
Accrued interest receivable	920	902
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	28	27
Financial Liabilities
Deposits with no stated maturity	147,330	141,976
Time deposits	11,995	13,253
Credit balances of factoring clients	1,145	1,016
Securities sold under customer repurchase agreements	450	367
Long-term borrowings	37,920	36,669
Accrued interest payable	107	134
Carrying Value | Qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	1	1
Financial Liabilities
Fair value of derivative financial instruments	0	0
Carrying Value | Non-qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	552	659
Financial Liabilities
Fair value of derivative financial instruments	541	625
Estimated Fair Value
Financial Assets
Cash and due from banks	812	814
Interest-earning deposits at banks	24,692	21,364
Securities purchased under agreements to resell	345	158
Investment in marketable equity securities	95	101
Investment securities available for sale	33,900	33,750
Investment securities held to maturity	8,973	8,702
Loans held for sale	185	82
Net loans	137,941	134,872
Accrued interest receivable	920	902
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	46	47
Financial Liabilities
Deposits with no stated maturity	147,330	141,976
Time deposits	11,986	13,247
Credit balances of factoring clients	1,145	1,016
Securities sold under customer repurchase agreements	450	367
Long-term borrowings	37,714	36,220
Accrued interest payable	107	134
Estimated Fair Value | Level 1
Financial Assets
Cash and due from banks	812	814
Interest-earning deposits at banks	24,692	21,364
Securities purchased under agreements to resell	0	0
Investment in marketable equity securities	42	48
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	345	158
Investment in marketable equity securities	53	53
Investment securities available for sale	33,732	33,582
Investment securities held to maturity	8,973	8,702
Loans held for sale	70	55
Net loans	1,491	1,463
Accrued interest receivable	920	902
Federal Home Loan Bank stock	20	20
Mortgage servicing rights	0	0
Financial Liabilities
Deposits with no stated maturity	147,330	141,976
Time deposits	11,986	13,247
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	450	367
Long-term borrowings	37,714	36,220
Accrued interest payable	107	134
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	168	168
Investment securities held to maturity	0	0
Loans held for sale	115	27
Net loans	136,450	133,409
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	46	47
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	1,145	1,016
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	1	1
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	1	1
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	552	659
Financial Liabilities
Fair value of derivative financial instruments	541	625
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	533	642
Financial Liabilities
Fair value of derivative financial instruments	540	624
Estimated Fair Value | Non-qualifying Hedges | Level 3
Financial Assets
Fair value of derivative financial instruments	19	17
Financial Liabilities
Fair value of derivative financial instruments	$ 1	$ 1