Investments (Amortized Cost and Fair Value of Nuclear Decommissioning Trusts) (Details) - Southern California Edison - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	$ 2,867	$ 2,784
Fair Value	4,352	4,242
Stocks
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	291	319
Fair Value	1,537	1,547
Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	645	659
Fair Value	753	766
U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	1,308	1,131
Fair Value	1,380	1,191
Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	552	600
Fair Value	608	659
Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	71	75
Fair Value	74	79
Repurchase agreement	$ 36	$ 114