INVESTMENT SECURITIES (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	$ 11	$ 2
Available-for-sale, less than 12 Months, estimated fair value	1,126	299
Available-for-sale, 12 Months or more	1,200	1,166
Available-for-sale, 12 months or more, estimated fair value	7,105	7,425
Available-for-sale, total	1,211	1,168
Available-for-sale, total, estimated fair value	8,231	7,724
U.S. Treasury securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	7	0
Available-for-sale, less than 12 Months, estimated fair value	795	99
Available-for-sale, 12 Months or more	109	106
Available-for-sale, 12 months or more, estimated fair value	292	296
Available-for-sale, total	116	106
Available-for-sale, total, estimated fair value	1,087	395
Agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	0	0
Available-for-sale, less than 12 Months, estimated fair value	5	7
Available-for-sale, 12 Months or more	16	15
Available-for-sale, 12 months or more, estimated fair value	263	288
Available-for-sale, total	16	15
Available-for-sale, total, estimated fair value	268	295
Agency guaranteed mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	2	2
Available-for-sale, less than 12 Months, estimated fair value	200	86
Available-for-sale, 12 Months or more	1,010	987
Available-for-sale, 12 months or more, estimated fair value	5,551	5,735
Available-for-sale, total	1,012	989
Available-for-sale, total, estimated fair value	5,751	5,821
Small Business Administration loan-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	0	0
Available-for-sale, less than 12 Months, estimated fair value	8	24
Available-for-sale, 12 Months or more	14	14
Available-for-sale, 12 months or more, estimated fair value	283	309
Available-for-sale, total	14	14
Available-for-sale, total, estimated fair value	291	333
Municipal securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	1	0
Available-for-sale, less than 12 Months, estimated fair value	104	68
Available-for-sale, 12 Months or more	51	44
Available-for-sale, 12 months or more, estimated fair value	716	797
Available-for-sale, total	52	44
Available-for-sale, total, estimated fair value	820	865
Other
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	1	0
Available-for-sale, less than 12 Months, estimated fair value	14	15
Available-for-sale, 12 Months or more	0	0
Available-for-sale, 12 months or more, estimated fair value	0	0
Available-for-sale, total	1	0
Available-for-sale, total, estimated fair value	$ 14	$ 15

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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