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Accumulated Other Comprehensive (Loss) Income - Schedule of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | $ (1,164) | $ (967)
Income Taxes | 284 | 232
Net of Income Taxes | (880) | (735)
Unrealized loss on securities available for sale |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | (1,175) | (972)
Income Taxes | 286 | 233
Net of Income Taxes | (889) | (739)
Unrealized loss on securities available for sale transferred to held to maturity |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | (7) | (8)
Income Taxes | 2 | 2
Net of Income Taxes | (5) | (6)
Defined benefit pension items |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Pretax | 18 | 13
Income Taxes | (4) | (3)
Net of Income Taxes | $ 14 | $ 10

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