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Asset Retirement Obligations (Details) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Mar. 31, 2024 | Sep. 30, 2023
Asset Retirement Obligations |  |
Asset Retirement Obligation, Period Increase (Decrease) | $ 103 |
Amortization and Depreciation of Decontaminating and Decommissioning Assets | 94 |
Asset Retirement Obligation, Beginning Balance | 7,489 |
Settlements | (122) |
Asset Retirement Obligation, Revision of Estimate | 92 |
Accretion (recorded as regulatory asset) | 133 |
Asset Retirement Obligation, Ending Balance | 7,592 |
Current portion of ARO | (311) | $ (272)
Revision in ARO estimate | (164) |
Gallatin Fossil Plant |  |
Asset Retirement Obligations |  |
Change in closure liabilities | 184 |
Cumberland Fossil Plant |  |
Asset Retirement Obligations |  |
Change in closure liabilities | 76 |
Nuclear |  |
Asset Retirement Obligations |  |
Asset Retirement Obligation, Beginning Balance | 3,808 |
Settlements | (3) |
Asset Retirement Obligation, Revision of Estimate | (161) |
Accretion Expense, Including Asset Retirement Obligations | 86 |
Asset Retirement Obligation, Ending Balance | 3,730 |
Non-nuclear |  |
Asset Retirement Obligations |  |
Asset Retirement Obligation, Beginning Balance | 3,681 |
Settlements | (119) |
Asset Retirement Obligation, Revision of Estimate | 253 |
Accretion (recorded as regulatory asset) | 47 |
Asset Retirement Obligation, Ending Balance | $ 3,862 |

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- Definition Reconciliation of Asset Retirement Obligations [Line Items] + References No definition available. + Details
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- Definition Amount of accretion expense, which includes, but is not limited to, accretion expense from asset retirement obligations, environmental remediation obligations, and other contingencies. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481879/410-20-45-1 + Details
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- Definition The current period expense charged against earnings on decontaminating and decommissioning of facilities used in the normal conduct of business and not intended for resale to allocate or recognize the cost of the assets over their useful lives. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 25 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481999/410-20-25-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Amount of increase (decrease) in asset retirement obligations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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- Definition Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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