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INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,783	$ 3,620
Gross Unrealized Gains	29	4
Gross Unrealized Losses	(85)	(158)
Fair Value	3,727	3,466
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	354	274
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	(1)
Fair Value	356	274
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	35	53
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	35	53
U.S. GSE
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	266	302
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(2)
Fair Value	266	300
Agency MBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	801	714
Gross Unrealized Gains	7	0
Gross Unrealized Losses	(8)	(20)
Fair Value	800	694
Agency CMO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	662	796
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(61)	(98)
Fair Value	601	698
Agency commercial MBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,595	1,420
Gross Unrealized Gains	19	3
Gross Unrealized Losses	(15)	(35)
Fair Value	1,599	1,388
States of the U.S. and political subdivisions (municipals)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20	24
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(2)
Fair Value	19	22
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	50	37
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Fair Value	$ 51	$ 37

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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