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Asset Retirement Obligations (Details) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Sep. 30, 2017
Asset Retirement Obligations |  |
Asset Retirement Obligation, Period Increase (Decrease) | $ 85 |
Amortization and Depreciation of Decontaminating and Decommissioning Assets | 72 |
Balance at September 30, 2017 | 4,304 |
Settlements | (42) |
Revisions in estimate | 45 |
Asset Retirement Obligation, Liabilities Incurred | 1 |
Accretion (recorded as regulatory asset) | 81 |
Balance at December 31, 2017 | 4,389 |
Nuclear |  |
Asset Retirement Obligations |  |
Balance at September 30, 2017 | 2,859 |
Settlements | 0 |
Revisions in estimate | 0 |
Asset Retirement Obligation, Liabilities Incurred | 0 |
Accretion (recorded as regulatory asset) | 65 |
Balance at December 31, 2017 | 2,924 |
Non-nuclear |  |
Asset Retirement Obligations |  |
Balance at September 30, 2017 | 1,445 |
Revisions in estimate | 45 |
Asset Retirement Obligation, Liabilities Incurred | 1 |
Accretion (recorded as regulatory asset) | 16 |
Balance at December 31, 2017 | 1,465 |
Accounts payable and accrued liabilities |  |
Asset Retirement Obligations |  |
Current portion of ARO | $ 142 | $ 128

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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 No definition available. + 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/presentationRef -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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- 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/2003/role/presentationRef -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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- Definition Amount of asset retirement obligations incurred during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 35 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846 + Details
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