INVESTMENT SECURITIES (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	$ 110	$ 2
Available-for-sale, less than 12 Months, estimated fair value	2,211	299
Available-for-sale, 12 Months or more	1,454	1,166
Available-for-sale, 12 months or more, estimated fair value	6,411	7,425
Available-for-sale, total	1,564	1,168
Available-for-sale, total, estimated fair value	8,622	7,724
U.S. Treasury securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	94	0
Available-for-sale, less than 12 Months, estimated fair value	1,797	99
Available-for-sale, 12 Months or more	133	106
Available-for-sale, 12 months or more, estimated fair value	268	296
Available-for-sale, total	227	106
Available-for-sale, total, estimated fair value	2,065	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	13	7
Available-for-sale, 12 Months or more	22	15
Available-for-sale, 12 months or more, estimated fair value	216	288
Available-for-sale, total	22	15
Available-for-sale, total, estimated fair value	229	295
Agency guaranteed mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	14	2
Available-for-sale, less than 12 Months, estimated fair value	301	86
Available-for-sale, 12 Months or more	1,204	987
Available-for-sale, 12 months or more, estimated fair value	5,017	5,735
Available-for-sale, total	1,218	989
Available-for-sale, total, estimated fair value	5,318	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	0	24
Available-for-sale, 12 Months or more	14	14
Available-for-sale, 12 months or more, estimated fair value	241	309
Available-for-sale, total	14	14
Available-for-sale, total, estimated fair value	241	333
Municipal securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, less than 12 Months	2	0
Available-for-sale, less than 12 Months, estimated fair value	85	68
Available-for-sale, 12 Months or more	81	44
Available-for-sale, 12 months or more, estimated fair value	669	797
Available-for-sale, total	83	44
Available-for-sale, total, estimated fair value	754	865
Other
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	15	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	0	0
Available-for-sale, total, estimated fair value	$ 15	$ 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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