OTHER COMPREHENSIVE INCOME - AOCI Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	$ 20,970	$ 19,563	$ 19,782	$ 19,398
Other comprehensive income (loss) before reclassifications	167	761	706	418
Amounts reclassified from AOCI to earnings	8	46	89	154
Other comprehensive income, net of tax	175	807	795	572
Balance, end of period	22,286	20,652	22,286	20,652
Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Debt securities transferred from available-for-sale			(45)	(52)
Unrealized gains (losses) on available-for-sale securities, net of hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(2,013)	(2,292)	(2,365)	(2,094)
Other comprehensive income (loss) before reclassifications	151	442	452	240
Amounts reclassified from AOCI to earnings	2	3	53	7
Other comprehensive income, net of tax	153	445	505	247
Balance, end of period	(1,860)	(1,847)	(1,860)	(1,847)
Net change related to cash flow hedges on loans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(7)	(399)	(267)	(363)
Other comprehensive income (loss) before reclassifications	17	317	247	178
Amounts reclassified from AOCI to earnings	6	43	36	146
Other comprehensive income, net of tax	23	360	283	324
Balance, end of period	16	(39)	16	(39)
Translation adjustments, net of hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(5)	(8)	(12)	(6)
Other comprehensive income (loss) before reclassifications	(1)	2	6	0
Amounts reclassified from AOCI to earnings	0	0	0	0
Other comprehensive income, net of tax	(1)	2	6	0
Balance, end of period	(6)	(6)	(6)	(6)
Unrealized losses for pension and other post-retirement obligations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(221)	(212)	(222)	(213)
Other comprehensive income (loss) before reclassifications	0	0	1	0
Amounts reclassified from AOCI to earnings	0	0	0	1
Other comprehensive income, net of tax	0	0	1	1
Balance, end of period	(221)	(212)	(221)	(212)
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(2,246)	(2,911)	(2,866)	(2,676)
Other comprehensive income, net of tax	175	807	795	572
Balance, end of period	$ (2,071)	$ (2,104)	$ (2,071)	$ (2,104)