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Plant Closures (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 18 Months Ended | 57 Months Ended
--- | --- | --- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Sep. 30, 2023
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Accelerated depreciation |  |  |  |  |  | $ 659,000,000
Depreciation expense | $ 463,000,000 | $ 482,000,000 | $ 1,400,000,000 | $ 1,400,000,000 |  |
Accumulated additional depreciation |  | $ 37,000,000 |  | $ 110,000,000 |  |
Property, Plant and Equipment [Member] |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Dispositions | 4 million | 3 million | 11 million |  |  |
Cumberland |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Accelerated depreciation | $ 16,000,000 |  |  |  |  |
Accumulated additional depreciation |  |  |  |  | $ 96,000,000 |

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