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ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount | $ 95 | $ 611 | $ 540 | $ 450
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax | (25) | (160) | (139) | (118)
Other comprehensive income, net of tax | 70 | 451 | 401 | 332
AOCI activity before reclassification, net amount |  |  | 404 | 329
Amounts reclassified from AOCI to earnings, net amount |  |  | (3) | 3
Unrealized loss on securities available for sale: |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount | 97 | 594 | 538 | 440
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax | (25) | (156) | (138) | (115)
Other comprehensive income, net of tax | 72 | 438 | 400 | 325
Unrealized loss on securities available for sale transferred to held to maturity |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Other comprehensive income, net of tax |  |  | 0 | 1
AOCI activity before reclassification, net amount |  |  | 0 | 0
Amounts reclassified from AOCI to earnings, gross amount | 1 | 1 | 1 | 1
Amounts reclassified from AOCI to earnings, tax | (1) | 0 | (1) | 0
Amounts reclassified from AOCI to earnings, net amount | 0 | 1 | 0 | 1
Defined benefit pension items |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount | (1) | 0 | (5) | (10)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax | 0 | 0 | 1 | 2
Other comprehensive income, net of tax | (1) | 0 | (4) | (8)
AOCI activity before reclassification, net amount |  |  | (4) | (8)
Amounts reclassified from AOCI to earnings, net amount |  |  | 0 | 0
Unrealized gain on cash flow hedge derivatives |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount | (2) | 16 | 6 | 19
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax | 1 | (4) | (1) | (5)
Other comprehensive income, net of tax | (1) | 12 | 5 | 14
AOCI activity before reclassification, gross amount | (2) | 14 | 10 | 17
AOCI activity before reclassification, tax | 1 | (4) | (2) | (5)
AOCI activity before reclassification, net amount | (1) | 10 | 8 | 12
Amounts reclassified from AOCI to earnings, gross amount | 0 | 2 | (4) | 2
Amounts reclassified from AOCI to earnings, tax | 0 | 0 | 1 | 0
Amounts reclassified from AOCI to earnings, net amount | $ 0 | $ 2 | $ (3) | $ 2

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