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Summary of Significant Accounting Policies (Property, Plant and Equipment and Asset Retirement Obligation) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014
Asset Retirement Obligation, Roll Forward |  |  |
Beginning balance |  | $ 2,821 |
Ending balance |  | 2,764 | $ 2,821
Southern California Edison |  |  |
Asset Retirement Obligation, Roll Forward |  |  |
Beginning balance |  | 2,819 | 3,418
Accretion | [1] | 173 | 192
Revisions |  | (14) | (790)
Liabilities settled |  | (216) | (1)
Ending balance |  | $ 2,762 | $ 2,819
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 |  | 43 years |
Southern California Edison | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives |  | 52 years |
Southern California Edison | General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives |  | 22 years |
Southern California Edison | Minimum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 5 years |
Southern California Edison | Minimum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 10 years |
Southern California Edison | Minimum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 20 years |
Southern California Edison | Minimum | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 40 years |
Southern California Edison | Minimum | General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 5 years |
Southern California Edison | Maximum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 15 years |
Southern California Edison | Maximum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 57 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 plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives |  | 60 years |
[1] | An ARO represents the present value of a future obligation. Accretion is an increase in the liability to account for the time value of money resulting from discounting.

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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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