Investments (Amortized Cost and Fair Value of Nuclear Decommissioning Trusts) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Nuclear Decommissioning Trusts Disclosures
Fair Value	$ 4,650	$ 4,562
Southern California Edison
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	2,470	2,447
Fair Value	4,650	4,562
Southern California Edison | Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	1,048	822
Southern California Edison | U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	707	996
Southern California Edison | Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	479	597
Southern California Edison | Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	236	32
Southern California Edison | Fair Value, Measurements, Recurring
Nuclear Decommissioning Trusts Disclosures
Fair Value	4,826	4,673
Southern California Edison | Fair Value, Measurements, Recurring | Stocks
Nuclear Decommissioning Trusts Disclosures
Fair Value	1,753	1,765
Southern California Edison | Fair Value, Measurements, Recurring | Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Fair Value	1,240	970
Southern California Edison | Fair Value, Measurements, Recurring | U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Fair Value	846	1,115
Southern California Edison | Fair Value, Measurements, Recurring | Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Fair Value	565	679
Southern California Edison | Fair Value, Measurements, Recurring | Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Fair Value	246	33
Repurchase agreements payable	$ 122	$ 41