FAIR VALUE - Schedule of Fair Value, Assets Measured on Nonrecurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	$ 110	$ 82
Loans - collateral dependent loans	141,924	134,872
Level 1 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Loans - collateral dependent loans	0	0
Level 2 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	80	55
Loans - collateral dependent loans	1,618	1,463
Level 3 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	30	27
Loans - collateral dependent loans	140,306	133,409
Fair Value, Nonrecurring | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	2	13
Loans - collateral dependent loans	181	388
Other real estate owned	76	16
Fair Value Measurements	259	417
Fair Value, Nonrecurring | Changes Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	(4)	(7)
Loans - collateral dependent loans	(141)	(171)
Other real estate owned	(1)	6
Fair Value Measurements	(146)	(172)
Fair Value, Nonrecurring | Level 1 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Loans - collateral dependent loans	0	0
Other real estate owned	0	0
Fair Value Measurements	0	0
Fair Value, Nonrecurring | Level 2 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Loans - collateral dependent loans	0	0
Other real estate owned	0	0
Fair Value Measurements	0	0
Fair Value, Nonrecurring | Level 3 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	2	13
Loans - collateral dependent loans	181	388
Other real estate owned	76	16
Fair Value Measurements	$ 259	$ 417