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Summary of Significant Accounting Policies (Nuclear Decommissioning and Asset Retirement Obligations) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Asset Retirement Obligation, Roll Forward |  |
Beginning balance | $ 2,590 |
Ending balance | 2,908 | $ 2,590
SCE |  |
Asset Retirement Obligation, Roll Forward |  |
Beginning balance | 2,586 | 2,762
Accretion | 166 | 157
Revisions | 376 | (165)
Liabilities settled | (236) | (168)
Ending balance | $ 2,892 | $ 2,586
Threshold period to be recognized as a loss for other-than-temporary impairment | 2 months |
SCE | Palo Verde and San Onofre Units |  |
Asset Retirement Obligation, Roll Forward |  |
Recorded liability to decommission nuclear power facilities | $ 2,600 |
Estimated cost to decommission nuclear facilities | $ 7,200 |
Decommissioning cost escalated rates, low end (percent) | 1.60% |
Decommissioning cost escalated rates, high end (percent) | 7.50% |
Estimated annual net of tax earnings, low end (percent) | 2.40% |
Estimated annual net of tax earnings, high end (percent) | 3.80% |

X
- Definition This element represents the asset retirement obligation for decommissioning active and inactive nuclear facilities at the balance sheet date. + References No definition available. + Details
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- Definition This element represents the high end of the range of the escalated rates under decommissioning cost methodology used for rate-making purpose. + References No definition available. + Details
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- Definition This element represents the low end of the range of the escalated rates under decommissioning cost methodology used for rate-making purpose. + References No definition available. + Details
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- Definition This element represents the total estimated cost to decommission its active nuclear facilities. + References No definition available. + Details
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- Definition This element represents the high end of the range of the estimated annual after-tax earnings on the decommissioning funds. + References No definition available. + Details
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- Definition This element represents the low end of the range of the estimated annual after-tax earnings on the decommissioning funds. + References No definition available. + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + 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)(3) -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 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + 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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- 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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- Definition Noncurrent 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 Threshold period for investment in equity securities in a continuous decline in value to be considered other than temporary impairment (OTTI), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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