Commitments and Contingencies (Contingencies) (Details) (USD $)	1 Months Ended		3 Months Ended	6 Months Ended			1 Months Ended	6 Months Ended			1 Months Ended
	Dec. 31, 2011	Jun. 30, 2010	Jun. 30, 2012	Jun. 30, 2012 sites	Jun. 30, 2011	Sep. 01, 2011	Oct. 31, 2011 Malibu Fire Order Instituting Investigation	Jun. 30, 2012 Insurance Claims	Jun. 30, 2012 San Onofre	Jun. 30, 2012 San Onofre Outage, Inspection and Repair Issues H	Oct. 31, 2011 OII Respondents Malibu Fire Order Instituting Investigation
Contingencies
Authorized expenditures										$ 525,000,000
Authorized expenditures, after adjustments for inflation										665,000,000
Ownership percentage (as a percentage)									78.21%
Costs incurred to date										593,000,000
Costs incurred for steam generator inspection and repair, current period										117,000,000
Collected customer rates, authorized operating costs, depreciation and return on investment										650,000,000
Rate base										1,200,000,000
Base rate, including construction work in progress										2,000,000,000
Required term, from notice of investigation to remove revenue requirements from customer rates										45 days
Continuous hours of operation, after which rates may be readjusted										100
Warranty period										20 years
MHI's limited liability under purchase agreement, excluding consequential damages										137,000,000
Loss Contingency, Damages Sought, Value	98,000,000						50,000,000				99,000,000
Maximum Expected Period for Clean Up of Identified Sites			30 years
Accrued liability for environmental remediation			43,000,000	43,000,000					11,000,000
Number of Sites Identified for Environmental Remediation				25
Minimum costs to be Identified Site				1,000,000
Number of Immaterial Sites for Environmental Remediation				33
Loss Contingency, Range of Possible Loss, Minimum			3,000,000	3,000,000
Environmental remediation liability			46,000,000	46,000,000
Environmental remediation liability, recorded as regulatory asset			43,000,000	43,000,000
Portion of Recorded Liability Recoverable From Incentive Mechanism				28,000,000
Percentage of Environmental Remediation Costs Recoverable From Incentive Mechanism				90.00%
Recorded Liability Incurred at Majority of Remaining Sites Through Customer Rates			15,000,000	15,000,000
Percentage of Environmental Remediation Costs to be Recovered				100.00%
Amount that Cleanup Costs for Identified Material Sites Could Exceed Recorded Liability				216,000,000
Amount that Cleanup Costs for Immaterial Sites Could Exceed Recorded Liability				6,000,000
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 Expense				4,000,000	7,000,000
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 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
Insurance Coverage for Wildfire Liabilities Limit						575,000,000
Increase In Self Insurance Retention Per Wildfire Occurence						10,000,000
Amount Of Damages Decision By US Court Of Federal Claims Spent Nuclear Fuel Litigation		$ 142,000,000