Fair Value Measurements (Quantitative Information About Level 3 Fair Value Measurements) (Details) - Southern California Edison - Level 3 $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) $ / MWh $ / MMBTU MW	Dec. 31, 2016 USD ($) $ / MWh $ / MMBTU MW
Congestion revenue rights | Market simulation model and auction prices
Quantitative Information About Level 3 Measurements [Line Items]
Fair Value, Assets | $	$ 55	$ 67
Fair Value, Liabilities | $	$ 0	$ 0
Congestion revenue rights | Market simulation model and auction prices | Load forecast | Minimum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, power units (in megawatts) | MW	3,708	3,708
Congestion revenue rights | Market simulation model and auction prices | Load forecast | Maximum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, power units (in megawatts) | MW	22,840	22,840
Congestion revenue rights | Market simulation model and auction prices | Power prices | Minimum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh)	3.65	3.65
Congestion revenue rights | Market simulation model and auction prices | Power prices | Maximum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh)	99.58	99.58
Congestion revenue rights | Market simulation model and auction prices | Gas prices | Minimum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh) | $ / MMBTU	2.51	2.51
Congestion revenue rights | Market simulation model and auction prices | Gas prices | Maximum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh) | $ / MMBTU	4.87	4.87
Tolling | Option model
Quantitative Information About Level 3 Measurements [Line Items]
Fair Value, Assets | $	$ 0	$ 0
Fair Value, Liabilities | $	$ 1,210	$ 1,154
Tolling | Option model | Power prices | Minimum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh)	18.01	23.40
Expected volatility rate (as a percent)	26.00%	29.00%
Tolling | Option model | Power prices | Maximum
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh)	45.28	51.24
Expected volatility rate (as a percent)	140.00%	71.00%
Tolling | Option model | Power prices | Weighted Average
Quantitative Information About Level 3 Measurements [Line Items]
Fair value inputs, price level ($ per MWh)	30.70	34.70
Expected volatility rate (as a percent)	36.00%	40.00%
Tolling | Option model | Gas prices | Minimum
Quantitative Information About Level 3 Measurements [Line Items]
Expected volatility rate (as a percent)	16.00%	15.00%
Tolling | Option model | Gas prices | Maximum
Quantitative Information About Level 3 Measurements [Line Items]
Expected volatility rate (as a percent)	39.00%	48.00%
Tolling | Option model | Gas prices | Weighted Average
Quantitative Information About Level 3 Measurements [Line Items]
Expected volatility rate (as a percent)	25.00%	20.00%