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Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) - SCE - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Property, Plant and Equipment [Line Items] |  |  |
Depreciation | $ 1,800 | $ 1,700 | $ 1,700
Depreciation expense stated as a percent of average original cost of depreciable utility plant (as a percent) | 3.60% | 3.60% | 3.70%
AFUDC equity capitalized during construction | $ 121 | $ 101 | $ 104
Interest and other income |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC equity capitalized during construction | 121 | 101 | 104
Interest expense |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC debt capitalized during construction | $ 53 | $ 63 | $ 44
Generation plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted Average Useful Lives | 36 years |  |
Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted Average Useful Lives | 48 years |  |
Transmission plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted Average Useful Lives | 54 years |  |
General plant and other |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Weighted Average Useful Lives | 25 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 | 45 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 | 55 years |  |
Maximum | Distribution plant |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated Useful Lives | 65 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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