INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Investment securities available for sale
Amortized Cost	$ 34,512	$ 20,688
Gross Unrealized Gains	81	115
Gross Unrealized Losses	(843)	(867)
Investment securities available for sale	33,750	19,936
Investment in marketable equity securities
Amortized Cost	79	75
Gross Unrealized Gains	27	17
Gross Unrealized Losses	(5)	(8)
Fair Value	101	84
Investment securities held to maturity
Amortized Cost	10,239	9,979
Gross Unrealized Gains	2	0
Gross Unrealized Losses	(1,539)	(1,476)
Fair Value	8,702	8,503
Total investment securities
Amortized Cost	44,830	30,742
Gross Unrealized Gains	110	132
Gross Unrealized Losses	(2,387)	(2,351)
Fair Value	42,553	28,523
U.S. Treasury
Investment securities available for sale
Amortized Cost	13,897	10,554
Gross Unrealized Gains	33	34
Gross Unrealized Losses	(27)	(80)
Investment securities available for sale	13,903	10,508
Investment securities held to maturity
Amortized Cost	483	479
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(31)	(40)
Fair Value	452	439
Government agency
Investment securities available for sale
Amortized Cost	79	120
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	(3)
Investment securities available for sale	77	117
Investment securities held to maturity
Amortized Cost	1,489	1,506
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(115)	(143)
Fair Value	1,374	1,363
Residential mortgage-backed securities
Investment securities available for sale
Amortized Cost	16,161	7,154
Gross Unrealized Gains	41	72
Gross Unrealized Losses	(582)	(540)
Investment securities available for sale	15,620	6,686
Investment securities held to maturity
Amortized Cost	4,558	4,205
Gross Unrealized Gains	2	0
Gross Unrealized Losses	(682)	(644)
Fair Value	3,878	3,561
Commercial mortgage-backed securities
Investment securities available for sale
Amortized Cost	3,869	2,319
Gross Unrealized Gains	7	9
Gross Unrealized Losses	(210)	(197)
Investment securities available for sale	3,666	2,131
Investment securities held to maturity
Amortized Cost	3,407	3,489
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(678)	(614)
Fair Value	2,729	2,875
Corporate bonds
Investment securities available for sale
Amortized Cost	489	529
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(22)	(47)
Investment securities available for sale	467	482
Municipal bonds
Investment securities available for sale
Amortized Cost	17	12
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available for sale	17	12
Supranational securities
Investment securities held to maturity
Amortized Cost	300	298
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(33)	(35)
Fair Value	267	263
Other
Investment securities held to maturity
Amortized Cost	2	2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 2	$ 2

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