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ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | $ (35) | $ (575)
Income Taxes | (9) | 130
Net of Income Taxes | (44) | (445)
Unrealized loss on securities available for sale |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | (224) | (762)
Income Taxes | 40 | 178
Net of Income Taxes | (184) | (584)
Unrealized loss on securities available for sale transferred to held to maturity |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | (5) | (6)
Income Taxes | 1 | 2
Net of Income Taxes | (4) | (4)
Defined benefit pension items |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | 177 | 182
Income Taxes | (46) | (47)
Net of Income Taxes | 131 | 135
Unrealized gain on cash flow hedge derivatives |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | 17 | 11
Income Taxes | (4) | (3)
Net of Income Taxes | $ 13 | $ 8

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