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INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 3,690 | $ 3,620
Gross Unrealized Gains | 27 | 4
Gross Unrealized Losses | (97) | (158)
Fair Value | 3,620 | 3,466
U.S. Treasury |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 274 | 274
Gross Unrealized Gains | 2 | 1
Gross Unrealized Losses | 0 | (1)
Fair Value | 276 | 274
U.S. government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 41 | 53
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 41 | 53
U.S. GSE |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 332 | 302
Gross Unrealized Gains | 1 | 0
Gross Unrealized Losses | (1) | (2)
Fair Value | 332 | 300
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 773 | 714
Gross Unrealized Gains | 6 | 0
Gross Unrealized Losses | (9) | (20)
Fair Value | 770 | 694
Agency CMO |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 694 | 796
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (68) | (98)
Fair Value | 626 | 698
Agency commercial MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,510 | 1,420
Gross Unrealized Gains | 17 | 3
Gross Unrealized Losses | (17) | (35)
Fair Value | 1,510 | 1,388
States of the U.S. and political subdivisions (municipals) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 21 | 24
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (2) | (2)
Fair Value | 19 | 22
Other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 45 | 37
Gross Unrealized Gains | 1 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | $ 46 | $ 37

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- Definition 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). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 + Details
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