INVESTMENT SECURITIES - Schedule of Fair Values and Unrealized Losses of Impaired Securities, by Length of Impairment (Details) $ in Millions	Mar. 31, 2026 USD ($) security	Dec. 31, 2025 USD ($) security
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	42	12
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	195	203
Debt securities, available-for-sale, number of positions \| security	237	215
Debt securities, available-for-sale, less than 12 months, fair value	$ 942	$ 251
Debt securities, available-for-sale, 12 months or longer, fair value	1,205	1,322
Debt securities, available-for-sale, fair value	2,147	1,573
Debt securities, available-for-sale, less than 12 months, unrealized losses	(9)	(1)
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(86)	(84)
Debt securities, available-for-sale, unrealized losses	$ (95)	$ (85)
U.S. Treasury
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	5
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	0
Debt securities, available-for-sale, number of positions \| security	5
Debt securities, available-for-sale, less than 12 months, fair value	$ 129
Debt securities, available-for-sale, 12 months or longer, fair value	0
Debt securities, available-for-sale, fair value	129
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	4	5
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	11	12
Debt securities, available-for-sale, number of positions \| security	15	17
Debt securities, available-for-sale, less than 12 months, fair value	$ 6	$ 8
Debt securities, available-for-sale, 12 months or longer, fair value	17	20
Debt securities, available-for-sale, fair value	23	28
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	6	2
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	3	3
Debt securities, available-for-sale, number of positions \| security	9	5
Debt securities, available-for-sale, less than 12 months, fair value	$ 164	$ 65
Debt securities, available-for-sale, 12 months or longer, fair value	51	51
Debt securities, available-for-sale, fair value	215	116
Debt securities, available-for-sale, less than 12 months, unrealized losses	(1)	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	0	0
Debt securities, available-for-sale, unrealized losses	$ (1)	$ 0
Agency MBS
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	8	1
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	86	90
Debt securities, available-for-sale, number of positions \| security	94	91
Debt securities, available-for-sale, less than 12 months, fair value	$ 228	$ 46
Debt securities, available-for-sale, 12 months or longer, fair value	204	251
Debt securities, available-for-sale, fair value	432	297
Debt securities, available-for-sale, less than 12 months, unrealized losses	(4)	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(8)	(8)
Debt securities, available-for-sale, unrealized losses	$ (12)	$ (8)
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	64	64
Debt securities, available-for-sale, number of positions \| security	64	64
Debt securities, available-for-sale, less than 12 months, fair value	$ 0	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	568	601
Debt securities, available-for-sale, fair value	568	601
Debt securities, available-for-sale, less than 12 months, unrealized losses	0	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(63)	(61)
Debt securities, available-for-sale, unrealized losses	$ (63)	$ (61)
Agency commercial MBS
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	13	4
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	21	22
Debt securities, available-for-sale, number of positions \| security	34	26
Debt securities, available-for-sale, less than 12 months, fair value	$ 377	$ 132
Debt securities, available-for-sale, 12 months or longer, fair value	344	371
Debt securities, available-for-sale, fair value	721	503
Debt securities, available-for-sale, less than 12 months, unrealized losses	(2)	(1)
Debt securities, available-for-sale, 12 months or longer, unrealized losses	(14)	(14)
Debt securities, available-for-sale, unrealized losses	$ (16)	$ (15)
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	7	9
Debt securities, available-for-sale, number of positions \| security	7	9
Debt securities, available-for-sale, less than 12 months, fair value	$ 0	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	12	19
Debt securities, available-for-sale, fair value	12	19
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)	(1)
Debt securities, available-for-sale, unrealized losses	$ (1)	$ (1)
Other debt securities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions \| security	6	0
Debt securities, available-for-sale, 12 months or longer, number of positions \| security	3	3
Debt securities, available-for-sale, number of positions \| security	9	3
Debt securities, available-for-sale, less than 12 months, fair value	$ 38	$ 0
Debt securities, available-for-sale, 12 months or longer, fair value	9	9
Debt securities, available-for-sale, fair value	47	9
Debt securities, available-for-sale, less than 12 months, unrealized losses	(1)	0
Debt securities, available-for-sale, 12 months or longer, unrealized losses	0	0
Debt securities, available-for-sale, unrealized losses	$ (1)	$ 0

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