DERIVATIVE FINANCIAL INSTRUMENTS - Hedging Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Derivatives, Fair Value [Line Items]
Notional Value	$ 45,059	$ 44,024
Asset derivatives included in accrued income and other assets
Total contracts	561	507
Liability derivatives included in accrued expenses and other liabilities
Total contracts	572	519
Accrued income and other assets
Asset derivatives included in accrued income and other assets
Total contracts	561	507
Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Total contracts	572	519
Interest rate contracts | Accrued income and other assets
Asset derivatives included in accrued income and other assets
Interest rate contracts designated as hedging instruments	89	109
Interest rate contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Interest rate contracts designated as hedging instruments	28	28
Foreign exchange contracts | Accrued income and other assets
Asset derivatives included in accrued income and other assets
Interest rate contracts designated as hedging instruments	0	4
Foreign exchange contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Interest rate contracts designated as hedging instruments	7	0
Credit contracts | Accrued income and other assets
Asset derivatives included in accrued income and other assets
Derivative instruments not designated as hedging instruments, asset	3	3
Credit contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Derivative credit and equity contracts not designated as hedging instruments, liability	0	0
Derivatives designated as Hedging Instruments | Interest rate contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	45,031	43,996
Derivatives designated as Hedging Instruments | Foreign exchange contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	278	809
Derivatives not designated as Hedging Instruments | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	111,926	103,047
Derivatives not designated as Hedging Instruments | Interest rate contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	56,363	49,284
Asset derivatives included in accrued income and other assets
Interest rate contracts not designated as hedging instruments	300	260
Derivatives not designated as Hedging Instruments | Interest rate contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Interest rate contracts not designated as hedging instruments	410	389
Derivatives not designated as Hedging Instruments | Foreign exchange contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	8,318	7,085
Asset derivatives included in accrued income and other assets
Foreign exchange contracts not designated as hedging instruments	98	58
Derivatives not designated as Hedging Instruments | Foreign exchange contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Foreign exchange contracts not designated as hedging instruments	73	60
Derivatives not designated as Hedging Instruments | Equity contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	801	912
Asset derivatives included in accrued income and other assets
Commodities contracts not designated as hedging instruments	18	33
Derivatives not designated as Hedging Instruments | Equity contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Commodities contracts not designated as hedging instruments	3	5
Derivatives not designated as Hedging Instruments | Commodities contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	1,021	822
Asset derivatives included in accrued income and other assets
Derivative instruments not designated as hedging instruments, asset	53	40
Derivatives not designated as Hedging Instruments | Commodities contracts | Accrued expenses and other liabilities
Liability derivatives included in accrued expenses and other liabilities
Derivative credit and equity contracts not designated as hedging instruments, liability	51	37
Derivatives not designated as Hedging Instruments | Credit contracts | Accrued income and other assets
Derivatives, Fair Value [Line Items]
Notional Value	$ 114	$ 139