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Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Asset Retirement Obligation, Roll Forward |  |  |
Ending balance | $ 2,782 | $ 2,610 |
Asset retirement obligations | 2,782 | 2,610 |
Southern California Edison |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Depreciation expense stated as a percent of average original cost of depreciable utility plant (percent) | 4.30% | 4.30% | 4.10%
Allowance for funds used during construction equity | 96 | 96 | 100
Allowance for funds used during construction debt | 40 | 42 | 41
Asset Retirement Obligation, Roll Forward |  |  |
Beginning balance | 2,610 | 2,507 |
Accretion expense | 161 | 62 |
Revisions | 12 | 42 |
Liabilities settled | (1) | (1) |
Ending balance | 2,782 | 2,610 | 2,507
Prudently incurred capital expenditure included in rate base during construction (as a percent) | 100.00% |  |
Asset retirement obligations | 2,782 | 2,610 | 2,507
Southern California Edison | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 38 years |  |
Southern California Edison | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 37 years |  |
Southern California Edison | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 46 years |  |
Southern California Edison | General and Other plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 23 years |  |
Southern California Edison | Minimum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 12 years |  |
Southern California Edison | Minimum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 30 years |  |
Southern California Edison | Minimum | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 35 years |  |
Southern California Edison | Minimum | General and Other plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 5 years |  |
Southern California Edison | Maximum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 70 years |  |
Southern California Edison | Maximum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 60 years |  |
Southern California Edison | Maximum | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 65 years |  |
Southern California Edison | Maximum | General and Other plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 60 years |  |
Southern California Edison | San Onofre and Palo Verde |  |  |
Asset Retirement Obligation, Roll Forward |  |  |
Ending balance | 2,700 | 2,500 |
Asset retirement obligations | $ 2,700 | $ 2,500 |

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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 Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 3, 10, 22 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: 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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