Investments (Amortized Cost and Fair Value of Nuclear Decommissioning Trusts) (Details) - Southern California Edison - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	$ 2,811	$ 2,917
Fair Value	4,376	4,331
Stocks
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	321	304
Fair Value	1,538	1,460
Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	653	691
Fair Value	813	840
U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	1,114	1,070
Fair Value	1,215	1,128
Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	656	708
Fair Value	740	755
Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	67	144
Fair Value	$ 70	148
Repurchase agreement		$ 81