INVESTMENT SECURITIES - Schedule of Unrealized Losses (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	$ 8,131	$ 1,517
Investment securities available for sale, less than 12 months, unrealized losses	(48)	(13)
Investment securities available for sale, 12 months or more, fair value	7,767	7,865
Investment securities available for sale, 12 months or more, unrealized losses	(879)	(854)
Investment securities available for sale, fair value	15,898	9,382
Investment securities available for sale, unrealized losses	(927)	(867)
U.S. Treasury
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	4,516	955
Investment securities available for sale, less than 12 months, unrealized losses	(9)	0
Investment securities available for sale, 12 months or more, fair value	1,929	1,919
Investment securities available for sale, 12 months or more, unrealized losses	(69)	(80)
Investment securities available for sale, fair value	6,445	2,874
Investment securities available for sale, unrealized losses	(78)	(80)
Government agency
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	0	23
Investment securities available for sale, less than 12 months, unrealized losses	0	0
Investment securities available for sale, 12 months or more, fair value	107	94
Investment securities available for sale, 12 months or more, unrealized losses	(3)	(3)
Investment securities available for sale, fair value	107	117
Investment securities available for sale, unrealized losses	(3)	(3)
Residential mortgage-backed securities
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	2,976	293
Investment securities available for sale, less than 12 months, unrealized losses	(28)	(3)
Investment securities available for sale, 12 months or more, fair value	3,969	4,073
Investment securities available for sale, 12 months or more, unrealized losses	(569)	(537)
Investment securities available for sale, fair value	6,945	4,366
Investment securities available for sale, unrealized losses	(597)	(540)
Commercial mortgage-backed securities
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	568	157
Investment securities available for sale, less than 12 months, unrealized losses	(4)	(1)
Investment securities available for sale, 12 months or more, fair value	1,346	1,386
Investment securities available for sale, 12 months or more, unrealized losses	(203)	(196)
Investment securities available for sale, fair value	1,914	1,543
Investment securities available for sale, unrealized losses	(207)	(197)
Corporate Bonds
Investment securities available for sale
Investment securities available for sale, less than 12 months, fair value	71	89
Investment securities available for sale, less than 12 months, unrealized losses	(7)	(9)
Investment securities available for sale, 12 months or more, fair value	416	393
Investment securities available for sale, 12 months or more, unrealized losses	(35)	(38)
Investment securities available for sale, fair value	487	482
Investment securities available for sale, unrealized losses	$ (42)	$ (47)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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