DERIVATIVES - Schedule of Other Derivative Activities (Details) - Not designated as hedging instrument - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	$ 123,444	$ 100,585
Asset derivatives Fair value	1,659	592
Liability derivatives Fair value	1,234	622
Mortgage banking derivatives
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	650	626
Asset derivatives Fair value	1	5
Liability derivatives Fair value	16	14
Customer-related derivatives
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	53,622	34,807
Asset derivatives Fair value	1,060	519
Liability derivatives Fair value	1,013	511
Customer-related derivatives \| Swaps receive fixed
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	19,323	12,310
Asset derivatives Fair value	9	42
Liability derivatives Fair value	878	336
Customer-related derivatives \| Swaps pay fixed
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	21,388	12,491
Asset derivatives Fair value	918	341
Liability derivatives Fair value	2	42
Customer-related derivatives \| Other
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	12,911	10,006
Asset derivatives Fair value	133	136
Liability derivatives Fair value	133	133
Other Derivative Activities \| Foreign exchange contracts
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	11,209	8,107
Asset derivatives Fair value	133	50
Liability derivatives Fair value	86	49
Other Derivative Activities \| Interest rate cap agreements
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	308	741
Asset derivatives Fair value	0	0
Liability derivatives Fair value	0	0
Other Derivative Activities \| Options for interest rate cap agreements
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	308	741
Asset derivatives Fair value	0	0
Liability derivatives Fair value	0	0
Other Derivative Activities \| TBA MBS forwards
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	30,082	23,256
Asset derivatives Fair value	431	18
Liability derivatives Fair value	46	2
Other Derivative Activities \| Other
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional	27,265	32,307
Asset derivatives Fair value	34	0
Liability derivatives Fair value	$ 73	$ 46