INVESTMENT SECURITIES - Schedule of Fair Values and Unrealized Losses of Impaired Securities, by Length of Impairment (Details) $ in Millions	Sep. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	14	43
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	208	213
Debt securities, available-for-sale, number of positions \| security	222	256
Debt securities, available-for-sale, less than 12 months, fair value	$ 186	$ 1,104
Debt securities, available-for-sale, 12 months or longer, fair value	1,485	1,670
Debt securities, available-for-sale, fair value	1,671	2,774
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	(10)
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(97)	(148)
Debt securities, available-for-sale, unrealized losses	$ (97)	$ (158)
U.S. Treasury
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security		3
Debt securities, available-for-sale, 12 months or longer, number of positions \| security		2
Debt securities, available-for-sale, number of positions \| security		5
Debt securities, available-for-sale, less than 12 months, fair value		$ 74
Debt securities, available-for-sale, 12 months or longer, fair value		75
Debt securities, available-for-sale, fair value		149
Debt securities, available-for-sale, less than 12 months, unrealized losses		(1)
Debt securities, available-for-sale, 12 months or longer, unrealized losses		0
Debt securities, available-for-sale, unrealized losses		$ (1)
U.S. government agencies
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	7	6
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	10	12
Debt securities, available-for-sale, number of positions \| security	17	18
Debt securities, available-for-sale, less than 12 months, fair value	$ 12	$ 11
Debt securities, available-for-sale, 12 months or longer, fair value	19	25
Debt securities, available-for-sale, fair value	31	36
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	0	0
Debt securities, available-for-sale, unrealized losses	$ 0	$ 0
U.S. GSE
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	1	2
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	5	7
Debt securities, available-for-sale, number of positions \| security	6	9
Debt securities, available-for-sale, less than 12 months, fair value	$ 30	$ 75
Debt securities, available-for-sale, 12 months or longer, fair value	101	126
Debt securities, available-for-sale, fair value	131	201
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(1)	(2)
Debt securities, available-for-sale, unrealized losses	$ (1)	$ (2)
Agency MBS
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	2	9
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	92	92
Debt securities, available-for-sale, number of positions \| security	94	101
Debt securities, available-for-sale, less than 12 months, fair value	$ 50	$ 235
Debt securities, available-for-sale, 12 months or longer, fair value	276	355
Debt securities, available-for-sale, fair value	326	590
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	(1)
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(9)	(19)
Debt securities, available-for-sale, unrealized losses	$ (9)	$ (20)
Agency CMO
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	0	0
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	65	66
Debt securities, available-for-sale, number of positions \| security	65	66
Debt securities, available-for-sale, less than 12 months, fair value	$ 0	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	626	698
Debt securities, available-for-sale, fair value	626	698
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(68)	(98)
Debt securities, available-for-sale, unrealized losses	$ (68)	$ (98)
Agency commercial MBS
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	3	23
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	24	20
Debt securities, available-for-sale, number of positions \| security	27	43
Debt securities, available-for-sale, less than 12 months, fair value	$ 90	$ 709
Debt securities, available-for-sale, 12 months or longer, fair value	435	359
Debt securities, available-for-sale, fair value	525	1,068
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	(8)
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(17)	(27)
Debt securities, available-for-sale, unrealized losses	$ (17)	$ (35)
States of the U.S. and political subdivisions (municipals)
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	0	0
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	9	10
Debt securities, available-for-sale, number of positions \| security	9	10
Debt securities, available-for-sale, less than 12 months, fair value	$ 0	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	19	22
Debt securities, available-for-sale, fair value	19	22
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(2)	(2)
Debt securities, available-for-sale, unrealized losses	$ (2)	$ (2)
Other debt securities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	1	0
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	3	4
Debt securities, available-for-sale, number of positions \| security	4	4
Debt securities, available-for-sale, less than 12 months, fair value	$ 4	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	9	10
Debt securities, available-for-sale, fair value	13	10
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	0	0
Debt securities, available-for-sale, unrealized losses	$ 0	$ 0

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