INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Investment Securities Held To Maturity [Line Items]
Amortized Cost	$ 4,251	$ 4,117
Gross Unrealized Gains	8	21
Gross Unrealized Losses	(210)	(197)
Fair Value	4,049	3,941
U.S. Treasury
Investment Securities Held To Maturity [Line Items]
Amortized Cost	1
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	1
Agency MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	847	784
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(59)	(55)
Fair Value	789	731
Agency CMO
Investment Securities Held To Maturity [Line Items]
Amortized Cost	565	612
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(65)	(62)
Fair Value	500	550
Agency commercial MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	1,841	1,715
Gross Unrealized Gains	6	18
Gross Unrealized Losses	(23)	(19)
Fair Value	1,824	1,714
States of the U.S. and political subdivisions (municipals)
Investment Securities Held To Maturity [Line Items]
Amortized Cost	946	982
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(62)	(60)
Fair Value	885	923
Other debt securities
Investment Securities Held To Maturity [Line Items]
Amortized Cost	51	24
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Fair Value	$ 50	$ 23

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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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