Commitments and Contingencies (Details) (USD $)	1 Months Ended		3 Months Ended				3 Months Ended	1 Months Ended	3 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended		3 Months Ended				3 Months Ended
	Jun. 30, 2010	Dec. 31, 2011 Southern California Edison	Mar. 31, 2013 Southern California Edison sites	Mar. 31, 2012 Southern California Edison	Sep. 15, 2012 Southern California Edison	Mar. 31, 2013 Southern California Edison Environmental Indemnities	Mar. 31, 2013 Edison International sites	Oct. 31, 2011 Alleged violations of PSD requirements and New Source Performance Standards of the CAA Southern California Edison private_environmental_organization	Mar. 31, 2013 Nuclear Insurance	Mar. 31, 2013 Nuclear Insurance Southern California Edison	Mar. 31, 2013 Nuclear Insurance SCE and other owners of San Onofre and Palo Verde	Oct. 31, 2011 Pending Litigation Malibu Fire Order Instituting Investigation	Dec. 31, 2007 Pending Litigation Malibu Fire Order Instituting Investigation power_pole	Oct. 30, 2011 Pending Litigation Malibu Fire Order Instituting Investigation Southern California Edison	Mar. 31, 2013 San Onofre (nuclear) Southern California Edison	Mar. 31, 2013 San Onofre (nuclear) Outage, Inspection and Repair Issues	Mar. 31, 2013 San Onofre (nuclear) Outage, Inspection and Repair Issues Southern California Edison invoices	Oct. 31, 2012 San Onofre (nuclear) Outage, Inspection and Repair Issues Southern California Edison	Dec. 31, 2005 San Onofre (nuclear) Outage, Inspection and Repair Issues Southern California Edison	Mar. 31, 2013 San Onofre and Palo Verde Nuclear Insurance Southern California Edison
Schedule Of Commitments And Contingencies [Line Items]
Maximum liability for purchase agreement for damages						$ 60,000,000											$ 138,000,000
Reduced power level of operation (as a percentage)																		70.00%
Term of reduced power level of operation (in months)																		5 months
Consecutive period of outage (months)																	9 months
Steam generators, warranted period																	20 years
Number of invoices for reimbursement																	5
Invoiced amount to MHI																	139,000,000
Invoiced amount paid by MHI																	45,000,000
Damages sought		98,000,000										99,000,000		50,000,000		234,000,000	183,000,000
Authorized expenditures																	728,000,000		525,000,000
Authorized expenditures, after adjustments for inflation																			665,000,000
Ownership percentage (as a percent)																	78.21%
Costs incurred to date																	602,000,000
Authorized expenditures by authoritative body, planned outage costs																	444,000,000
Authorized expenditures by authoritative body, planned outage costs																	50,000,000
Incremental inspection and repair costs																	109,000,000
Incremental inspection and repair costs, payments from MHI																	36,000,000
Number of failed power poles (in power poles)													3
Number of plaintiffs (entities)								4
Identified material sites for environmental remediation (in number of sites)							23
Minimum costs to be Identified Site							1,000,000
Minimum liability for environmental remediation for material sites			124,000,000												91,000,000
Immaterial sites for environmental remediation (in number of sites)			35
Immaterial sites, range of liability, minimum			3,000,000
Environmental remediation liability			127,000,000
Regulatory assets related to environmental remediation			123,000,000
Portion of recorded liability recoverable from incentive mechanism			31,000,000
Percentage of environmental remediation costs recoverable through an incentive mechanism (as a percent)			90.00%
Liability incurred at majority of the remaining sites through customer rates			92,000,000
Environmental remediation costs to be recovered (as a percent)			100.00%
Amount that cleanup costs could exceed recorded liability for identified material sites			180,000,000
Amount that cleanup costs could exceed recorded liability for immaterial sites			6,000,000
Maximum expected period for cleanup of identified sites (in years)			30 years
Expected annual environmental remediation costs, low end of range			6,000,000
Expected annual environmental remediation costs, high end of range			28,000,000
Environmental remediation costs			2,000,000	2,000,000
Federal limit on public liability claims from nuclear incident, approximate									12,600,000,000
Private primary insurance purchased											375,000,000
Maximum assessment 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										52,000,000
Insurance coverage for wildfire liabilities Limit					550,000,000
Self insurance retention per wildfire occurrence					10,000,000
Amount of damages, decision by US Court of Federal Claims, spent nuclear fuel litigation	$ 142,000,000