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Asset Retirement Obligations Asset Retirement Obligations (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Aug. 01, 2017
Liabilities Settled [Line Items] |  |  |  |
Increase in ARO liability |  | $ 837 |  |
Change in estimate | [1] | 50 | $ 430 |
Costs for asbestos |  | 114 |  |
Allen West ARO increase |  | 33 |  |
Paradise ARO increase (decrease) |  | 57 |  |
Allen East ARO increase (decrease) |  | 44 |  |
Gallatin CCR ARO increase (decrease) |  | 672 |  |
Additional obligations | [1] | 18 | 1 |
Gallatin CCR | [1] | 672 |  |
Gallatin CCR regulatory asset |  |  |  | $ 900
Balance | [1] | 5,616 | 4,779 |
Asset Retirement Obligation, Liabilities Settled | [1] | 89 | 106 |
Accretion (recorded as regulatory asset) | [1] | 186 | 165 |
Asset disposition | [1] |  | (15) |
Gain (Loss) on Disposition of Assets |  | 5 |  |
Amortization and Depreciation of Decontaminating and Decommissioning Assets |  | 144 |  |
Accounts payable and accrued liabilities |  |  |  |
Liabilities Settled [Line Items] |  |  |  |
Current portion of ARO |  | 163 | 115 |
Nuclear |  |  |  |
Liabilities Settled [Line Items] |  |  |  |
Revision of estimate (other non nuclear) |  | 0 | (250) |
Change in estimate |  |  | 0 |
Additional obligations |  | 18 | 0 |
Gallatin CCR |  | 0 |  |
Balance |  | 3,136 | 2,989 |
Asset Retirement Obligation, Liabilities Settled |  | 7 | 0 |
Accretion (recorded as regulatory asset) |  | 136 | 130 |
Asset disposition |  |  | 0 |
Non-nuclear |  |  |  |
Liabilities Settled [Line Items] |  |  |  |
Change in estimate |  | 50 | 430 |
Additional obligations |  | 0 | 1 |
Gallatin CCR |  | 672 |  |
Balance |  | 2,480 | 1,790 |
Asset Retirement Obligation, Liabilities Settled |  | 82 | 106 |
Accretion (recorded as regulatory asset) |  | $ 50 | 35 |
Asset disposition |  |  | $ (15) |
[1] | (1) The current portions of the ARO liability in the amounts of $163 million and $115 million at September 30, 2019 and 2018, respectively, are included in Accounts payable and accrued liabilities.

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- Definition Allen East ARO increase (decrease) + References No definition available. + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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