Commitments and Contingencies (Contingencies) (Details) (USD $)	3 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended		3 Months Ended				3 Months Ended	1 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Nuclear Insurance	Oct. 31, 2011 Malibu Fire Order Instituting Investigation	Mar. 31, 2012 Edison International sites	Dec. 31, 2011 Southern California Edison Company	Jun. 30, 2010 Southern California Edison Company	Mar. 31, 2012 Southern California Edison Company sites	Mar. 31, 2011 Southern California Edison Company	Sep. 01, 2011 Southern California Edison Company	Mar. 31, 2012 Southern California Edison Company San Onofre (nuclear)	Mar. 31, 2012 Southern California Edison Company Nuclear Insurance	Oct. 30, 2011 Southern California Edison Company Malibu Fire Order Instituting Investigation	Jan. 31, 2012 Midwest Generation LLC. claims	Oct. 31, 2011 Midwest Generation LLC. claims	Mar. 31, 2012 Midwest Generation LLC. sites	Aug. 31, 2009 Midwest Generation LLC. Violation of certain operating permit requirements sites	Mar. 31, 2012 Midwest Generation LLC. Violation of certain operating permit requirements claims	Jan. 31, 2011 Homer City Violations of the PSD and Title V provisions of the CAA owners residents	Mar. 31, 2012 SCE and other owners of San Onofre and Palo Verde Nuclear Insurance
Contingencies
Number of coal-fired electric generating stations																	6
Penalties sought, per violation, per day, minimum end of range																	$ 25,000		$ 32,500
Penalties sought, per violation, per day, maximum end of range																	37,500		37,500
Number of fully dismissed claims in the complaint filed by the US EPA and the State of Illinois																		9
Number of claims in the complaint filed by the US EPA and the State of Illinois																		10
Number of complaints filed asserting claims of nuisance, negligence, trespass, and strict liability														2
Similar number of complaints previously filed asserting claims of nuisance, negligence, trespass, and strict liability that were dismissed															2
Number of plaintiffs																			2
Number of prior owners of facilities																			2
Damages sought				99,000,000		98,000,000							50,000,000
Identified material sites for environmental remediation (in number of sites)					27			25								2
Identified material sites, minimum amount of upper end of range of costs					1,000,000
Minimum liability for environmental remediation					51,000,000			43,000,000			12,000,000
Amount that cleanup costs could exceed recorded liability for identified material sites					214,000,000
Amount that cleanup costs could exceed recorded liability for immaterial sites								5,000,000
Immaterial sites for environmental remediation (in number of sites)								33
Immaterial sites, range of liability, minimum								3,000,000
Environmental remediation liability								46,000,000
Percentage of environmental remediation costs recoverable through an incentive mechanism (as a percent)								90.00%
Portion of recorded liability recoverable from incentive mechanism								27,000,000
Environmental remediation costs to be recovered (as a percent)								100.00%
Liability incurred at majority of the remaining sites through customer rates								16,000,000
Regulatory assets	5,713,000,000	5,466,000,000						43,000,000
Maximum expected period for cleanup of identified sites (in years)								30 years
Expected annual environmental remediation costs, low end of range								7,000,000
Expected annual environmental remediation costs, high end of range								17,000,000
Environmental remediation costs								2,000,000	4,000,000
Federal limit on public liability claims from nuclear incident, approximate			12,600,000,000
Private primary insurance purchased																				375,000,000
Maximum deferred insurance premium per each nuclear incident												235,000,000
Maximum yearly assessment per nuclear incident												35,000,000
Loss limit, property damage insurance												500,000,000
Loss limit, property damage insurance, federal minimum requirement	1,100,000,000
Limit on assessment of retrospective premium adjustments, per year, approximate												49,000,000
Amount of damages, decision by US Court of Federal Claims, spent nuclear fuel litigation							142,000,000
Insurance Coverage for Wildfire Liabilities Limit										575,000,000
Increase In Self Insurance Retention Per Wildfire Occurence										$ 10,000,000