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Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) - SCE - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Property, Plant and Equipment [Line Items] |  |  |
Depreciation | $ 1,650 | $ 1,610 | $ 1,520
Depreciation expense stated as a percent of average original cost of depreciable utility plant (percent) | 3.70% | 3.80% | 3.80%
AFUDC equity capitalized during construction | $ 104 | $ 87 | $ 74
Interest and other income |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC equity capitalized during construction | 104 | 87 | 74
Interest expense |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC debt capitalized during construction | $ 44 | $ 28 | $ 23
Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 37 years |  |
Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 43 years |  |
Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 52 years |  |
General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted-Average Useful Lives | 22 years |  |
Minimum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 10 years |  |
Minimum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 20 years |  |
Minimum | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 40 years |  |
Minimum | General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 5 years |  |
Maximum | Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 54 years |  |
Maximum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 60 years |  |
Maximum | Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 65 years |  |
Maximum | General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 60 years |  |

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