DERIVATIVE FINANCIAL INSTRUMENTS - Asset and Liability Management (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Notional Disclosures [Abstract]
Notional Value	$ 42,311		$ 42,311		$ 45,809
Increase (decrease) to net interest income due to derivative adjustment	(38)	$ (57)	(63)	$ (195)
Other long term debt
Notional Disclosures [Abstract]
Notional Value	10,599		10,599		11,347
Not Designated as Hedging Instrument, Economic Hedge
Notional Disclosures [Abstract]
Notional Value	175		175		175
Not Designated as Hedging Instrument, Economic Hedge | Other long term debt
Notional Disclosures [Abstract]
Notional Value	0		0		0
Fair Value Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	15,886		15,886		22,334
Fair Value Hedges | Derivatives designated as Hedging Instruments | Other long term debt
Notional Disclosures [Abstract]
Notional Value	10,599		10,599		11,347
Cash Flow Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	26,250		26,250		23,300
Cash Flow Hedges | Derivatives designated as Hedging Instruments | Other long term debt
Notional Disclosures [Abstract]
Notional Value	0		0		0
Investment securities
Notional Disclosures [Abstract]
Notional Value	5,287		5,287		10,987
Investment securities | Not Designated as Hedging Instrument, Economic Hedge
Notional Disclosures [Abstract]
Notional Value	0		0		0
Investment securities | Fair Value Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	5,287		5,287		10,987
Investment securities | Cash Flow Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	0		0		0
Loans
Notional Disclosures [Abstract]
Notional Value	26,425		26,425		23,475
Loans | Not Designated as Hedging Instrument, Economic Hedge
Notional Disclosures [Abstract]
Notional Value	175		175		175
Loans | Fair Value Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	0		0		0
Loans | Cash Flow Hedges | Derivatives designated as Hedging Instruments
Notional Disclosures [Abstract]
Notional Value	$ 26,250		$ 26,250		$ 23,300