INVESTMENT AND OTHER SECURITIES - Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Available-for-sale securities:
Less than 12 Months, Fair Value	$ 18,901	$ 1,198
Less than 12 Months, Gross Unrealized Losses	(385)	(14)
Over 12 Months, Fair Value	14,242	16,499
Over 12 Months, Gross Unrealized Losses	(3,166)	(2,430)
Total, Fair Value	33,143	17,697
Total, Gross Unrealized Losses	(3,551)	(2,444)
Held-to-maturity securities:
Less than 12 Months, Fair Value	2,954	48
Less than 12 Months, Gross Unrealized Losses	(55)	0
Over 12 Months, Fair Value	9,289	11,079
Over 12 Months, Gross Unrealized Losses	(2,212)	(1,647)
Total held-to-maturity securities	12,243	11,127
Total, Gross Unrealized Losses	(2,267)	(1,647)
U.S. Treasury
Available-for-sale securities:
Less than 12 Months, Fair Value	8,111	0
Less than 12 Months, Gross Unrealized Losses	(100)	0
Over 12 Months, Fair Value	0	439
Over 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	8,111	439
Total, Gross Unrealized Losses	(100)	0
Held-to-maturity securities:
Less than 12 Months, Fair Value	2,143	0
Less than 12 Months, Gross Unrealized Losses	(29)	0
Over 12 Months, Fair Value	0	289
Over 12 Months, Gross Unrealized Losses	0	0
Total held-to-maturity securities	2,143	289
Total, Gross Unrealized Losses	(29)	0
Total U.S. Treasury, federal agency, and other agency securities
Available-for-sale securities:
Less than 12 Months, Fair Value	16,705	144
Less than 12 Months, Gross Unrealized Losses	(316)	0
Over 12 Months, Fair Value	11,834	14,145
Over 12 Months, Gross Unrealized Losses	(3,004)	(2,333)
Total, Fair Value	28,539	14,289
Total, Gross Unrealized Losses	(3,320)	(2,333)
Held-to-maturity securities:
Less than 12 Months, Fair Value	2,954	48
Less than 12 Months, Gross Unrealized Losses	(55)	0
Over 12 Months, Fair Value	9,288	11,078
Over 12 Months, Gross Unrealized Losses	(2,212)	(1,647)
Total held-to-maturity securities	12,242	11,126
Total, Gross Unrealized Losses	(2,267)	(1,647)
Residential MBS
Available-for-sale securities:
Less than 12 Months, Fair Value	3,829	55
Less than 12 Months, Gross Unrealized Losses	(110)	0
Over 12 Months, Fair Value	7,972	9,185
Over 12 Months, Gross Unrealized Losses	(1,781)	(1,365)
Total, Fair Value	11,801	9,240
Total, Gross Unrealized Losses	(1,891)	(1,365)
Held-to-maturity securities:
Less than 12 Months, Fair Value	431	0
Less than 12 Months, Gross Unrealized Losses	(13)	0
Over 12 Months, Fair Value	5,747	6,694
Over 12 Months, Gross Unrealized Losses	(1,305)	(941)
Total held-to-maturity securities	6,178	6,694
Total, Gross Unrealized Losses	(1,318)	(941)
Residential CMO
Available-for-sale securities:
Less than 12 Months, Fair Value	3,948	51
Less than 12 Months, Gross Unrealized Losses	(89)	0
Over 12 Months, Fair Value	2,166	2,665
Over 12 Months, Gross Unrealized Losses	(432)	(308)
Total, Fair Value	6,114	2,716
Total, Gross Unrealized Losses	(521)	(308)
Held-to-maturity securities:
Less than 12 Months, Fair Value	366	48
Less than 12 Months, Gross Unrealized Losses	(12)	0
Over 12 Months, Fair Value	2,554	2,956
Over 12 Months, Gross Unrealized Losses	(672)	(520)
Total held-to-maturity securities	2,920	3,004
Total, Gross Unrealized Losses	(684)	(520)
Commercial MBS
Available-for-sale securities:
Less than 12 Months, Fair Value	756	23
Less than 12 Months, Gross Unrealized Losses	(16)	0
Over 12 Months, Fair Value	1,631	1,782
Over 12 Months, Gross Unrealized Losses	(789)	(657)
Total, Fair Value	2,387	1,805
Total, Gross Unrealized Losses	(805)	(657)
Held-to-maturity securities:
Less than 12 Months, Fair Value	14	0
Less than 12 Months, Gross Unrealized Losses	(1)	0
Over 12 Months, Fair Value	957	1,094
Over 12 Months, Gross Unrealized Losses	(232)	(184)
Total held-to-maturity securities	971	1,094
Total, Gross Unrealized Losses	(233)	(184)
Other agencies
Available-for-sale securities:
Less than 12 Months, Fair Value	61	15
Less than 12 Months, Gross Unrealized Losses	(1)	0
Over 12 Months, Fair Value	65	74
Over 12 Months, Gross Unrealized Losses	(2)	(3)
Total, Fair Value	126	89
Total, Gross Unrealized Losses	(3)	(3)
Held-to-maturity securities:
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Gross Unrealized Losses	0	0
Over 12 Months, Fair Value	30	45
Over 12 Months, Gross Unrealized Losses	(3)	(2)
Total held-to-maturity securities	30	45
Total, Gross Unrealized Losses	(3)	(2)
Municipal securities
Available-for-sale securities:
Less than 12 Months, Fair Value	2,191	1,043
Less than 12 Months, Gross Unrealized Losses	(69)	(14)
Over 12 Months, Fair Value	2,020	1,892
Over 12 Months, Gross Unrealized Losses	(124)	(67)
Total, Fair Value	4,211	2,935
Total, Gross Unrealized Losses	(193)	(81)
Held-to-maturity securities:
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Gross Unrealized Losses	0	0
Over 12 Months, Fair Value	1	1
Over 12 Months, Gross Unrealized Losses	0	0
Total held-to-maturity securities	1	1
Total, Gross Unrealized Losses	0	0
Corporate debt
Available-for-sale securities:
Less than 12 Months, Fair Value	0	2
Less than 12 Months, Gross Unrealized Losses	0	0
Over 12 Months, Fair Value	165	176
Over 12 Months, Gross Unrealized Losses	(21)	(15)
Total, Fair Value	165	178
Total, Gross Unrealized Losses	(21)	(15)
Asset-backed securities
Available-for-sale securities:
Less than 12 Months, Fair Value	2	9
Less than 12 Months, Gross Unrealized Losses	0	0
Over 12 Months, Fair Value	158	207
Over 12 Months, Gross Unrealized Losses	(7)	(8)
Total, Fair Value	160	216
Total, Gross Unrealized Losses	(7)	(8)
Private-label CMO
Available-for-sale securities:
Less than 12 Months, Fair Value	3	0
Less than 12 Months, Gross Unrealized Losses	0	0
Over 12 Months, Fair Value	65	79
Over 12 Months, Gross Unrealized Losses	(10)	(7)
Total, Fair Value	68	79
Total, Gross Unrealized Losses	$ (10)	$ (7)

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