INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Investment Securities Held To Maturity [Line Items]
Amortized Cost	$ 4,117	$ 3,979
Gross Unrealized Gains	21	3
Gross Unrealized Losses	(197)	(338)
Fair Value	3,941	3,644
U.S. Treasury
Investment Securities Held To Maturity [Line Items]
Amortized Cost		1
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		1
U.S. GSE
Investment Securities Held To Maturity [Line Items]
Amortized Cost		29
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		29
Agency MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	784	901
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(55)	(96)
Fair Value	731	806
Agency CMO
Investment Securities Held To Maturity [Line Items]
Amortized Cost	612	714
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(62)	(95)
Fair Value	550	619
Agency commercial MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	1,715	1,326
Gross Unrealized Gains	18	2
Gross Unrealized Losses	(19)	(44)
Fair Value	1,714	1,284
States of the U.S. and political subdivisions (municipals)
Investment Securities Held To Maturity [Line Items]
Amortized Cost	982	992
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(60)	(103)
Fair Value	923	889
Other debt securities
Investment Securities Held To Maturity [Line Items]
Amortized Cost	24	16
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	$ 23	$ 16

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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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