FAIR VALUE - Schedule of Carrying Values and Estimated Fair Values for Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Financial Assets
Investment in marketable equity securities	$ 97	$ 101
Investment securities available for sale	33,060	33,750
Investment securities held to maturity	10,189	10,239
Fair value of derivative financial instruments	626	660
Financial Liabilities
Fair value of derivative financial instruments	631	625
Carrying Value
Financial Assets
Cash and due from banks	889	814
Interest-earning deposits at banks	26,184	21,364
Securities purchased under agreements to resell	300	158
Investment in marketable equity securities	97	101
Investment securities available for sale	33,060	33,750
Investment securities held to maturity	10,189	10,239
Loans held for sale	123	82
Net loans	137,605	136,567
Accrued interest receivable	902	902
Federal Home Loan Bank stock	19	20
Mortgage servicing rights	29	27
Financial Liabilities
Deposits with no stated maturity	148,693	141,976
Time deposits	11,242	13,253
Credit balances of factoring clients	1,077	1,016
Securities sold under customer repurchase agreements	471	367
Long-term borrowings	37,578	36,669
Accrued interest payable	120	134
Carrying Value | Qualifying Hedges
Financial Assets
Fair value of derivative financial instruments		1
Carrying Value | Non-qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	626	659
Financial Liabilities
Fair value of derivative financial instruments	631	625
Estimated Fair Value
Financial Assets
Cash and due from banks	889	814
Interest-earning deposits at banks	26,184	21,364
Securities purchased under agreements to resell	300	158
Investment in marketable equity securities	97	101
Investment securities available for sale	33,060	33,750
Investment securities held to maturity	8,888	8,702
Loans held for sale	123	82
Net loans	138,120	134,872
Accrued interest receivable	902	902
Federal Home Loan Bank stock	19	20
Mortgage servicing rights	48	47
Financial Liabilities
Deposits with no stated maturity	148,693	141,976
Time deposits	11,244	13,247
Credit balances of factoring clients	1,077	1,016
Securities sold under customer repurchase agreements	471	367
Long-term borrowings	37,507	36,220
Accrued interest payable	120	134
Estimated Fair Value | Level 1
Financial Assets
Cash and due from banks	889	814
Interest-earning deposits at banks	26,184	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	300	158
Investment in marketable equity securities	55	53
Investment securities available for sale	32,922	33,582
Investment securities held to maturity	8,888	8,702
Loans held for sale	83	55
Net loans	1,538	1,463
Accrued interest receivable	902	902
Federal Home Loan Bank stock	19	20
Mortgage servicing rights	0	0
Financial Liabilities
Deposits with no stated maturity	148,693	141,976
Time deposits	11,244	13,247
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	471	367
Long-term borrowings	37,507	36,220
Accrued interest payable	120	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	138	168
Investment securities held to maturity	0	0
Loans held for sale	40	27
Net loans	136,582	133,409
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	48	47
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	1,077	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
Estimated Fair Value | Qualifying Hedges | Level 1
Financial Assets
Fair value of derivative financial instruments		0
Estimated Fair Value | Qualifying Hedges | Level 2
Financial Assets
Fair value of derivative financial instruments		1
Estimated Fair Value | Qualifying Hedges | Level 3
Financial Assets
Fair value of derivative financial instruments		0
Estimated Fair Value | Non-qualifying Hedges
Financial Assets
Fair value of derivative financial instruments	626	659
Financial Liabilities
Fair value of derivative financial instruments	631	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	603	642
Financial Liabilities
Fair value of derivative financial instruments	630	624
Estimated Fair Value | Non-qualifying Hedges | Level 3
Financial Assets
Fair value of derivative financial instruments	23	17
Financial Liabilities
Fair value of derivative financial instruments	$ 1	$ 1