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Plant Closures (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended | 27 Months Ended
--- | --- | --- | --- | ---
Mar. 31, 2025 | Mar. 31, 2024 | Mar. 31, 2025 | Mar. 31, 2024 | Mar. 31, 2025 | Mar. 31, 2025
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Depreciation expense | $ 475 | $ 450 | $ 945 | $ 902 |  |
Kingston |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Accelerated depreciation |  |  |  |  | $ 9 |
Accumulated additional depreciation |  |  |  |  | $ 36 |
Cumberland |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Accelerated depreciation | $ 16 |  |  |  |  |
Accumulated additional depreciation |  |  |  |  |  | $ 144

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