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Asset Retirement Obligations (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017
Asset Retirement Obligations |  |
Asset Retirement Obligation, Period Increase (Decrease) | $ 61 |
Amortization and Depreciation of Decontaminating and Decommissioning Assets | 36 |
Balance at September 30, 2017 | 4,304 |
Settlements | (25) |
Revisions in estimate | 46 |
Accretion (recorded as regulatory asset) | 40 |
Balance at December 31, 2017 | 4,365 |
Nuclear |  |
Asset Retirement Obligations |  |
Balance at September 30, 2017 | 2,859 |
Settlements | 0 |
Revisions in estimate | 0 |
Accretion (recorded as regulatory asset) | 32 |
Balance at December 31, 2017 | 2,891 |
Non-nuclear |  |
Asset Retirement Obligations |  |
Balance at September 30, 2017 | 1,445 |
Settlements | (25) |
Revisions in estimate | 46 |
Accretion (recorded as regulatory asset) | 8 |
Balance at December 31, 2017 | 1,474 |
Accounts payable and accrued liabilities |  |
Asset Retirement Obligations |  |
Current portion of ARO | $ 159 | $ 128

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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 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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