Debt and Credit Agreements (Schedule of First and Refunding Mortgage Bonds) (Details) - Southern California Edison - First and refunding mortgage bonds - USD ($) $ in Millions	Aug. 31, 2018	Jun. 30, 2018	Mar. 31, 2018
2.90% First and refunding mortgage bonds due 2021
Debt Instrument [Line Items]
Stated interest rate			2.90%
Debt			$ 450
3.65% First and refunding mortgage bonds due 2028
Debt Instrument [Line Items]
Stated interest rate			3.65%
Debt			$ 400
3.40% First and refunding mortgage bonds due 2023
Debt Instrument [Line Items]
Stated interest rate		3.40%
Debt		$ 300
3.70% First and refunding mortgage bonds due 2025
Debt Instrument [Line Items]
Stated interest rate	3.70%
Debt	$ 300
4.125% First and refunding mortgage bonds due 2048
Debt Instrument [Line Items]
Debt		$ 1,300
4.125% First and refunding mortgage bonds due 2048, issued March 2018
Debt Instrument [Line Items]
Stated interest rate			4.125%
Debt			$ 400
4.125% First and refunding mortgage bonds due 2048, issued June 2018
Debt Instrument [Line Items]
Stated interest rate		4.125%
Debt		$ 350
4.125% First and refunding mortgage bonds due 2048, issued August 2018
Debt Instrument [Line Items]
Stated interest rate	4.125%
Debt	$ 550