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Commitments and Contingencies (Environmental Remediation) (Details) - Southern California Edison $ in Millions | 3 Months Ended
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Mar. 31, 2018 USD ($) site | Mar. 31, 2017 USD ($)
Schedule Of Commitments And Contingencies [Line Items] |  |
Minimum costs to be identified site | $ 1 |
Minimum liability for environmental remediation | 146 |
Regulatory assets related to environmental remediation | 140 |
Portion of recorded liability recoverable from incentive mechanism | $ 47 |
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 | $ 93 |
Environmental remediation costs to be recovered (as a percent) | 100.00% |
Amount that cleanup costs could exceed recorded liability for identified material sites | $ 131 |
Amount that cleanup costs could exceed recorded liability for immaterial sites | $ 8 |
Clean up (period) | 30 years |
Remediation cost estimates (period) | 5 years |
Expected remediation costs for each of the next four years, low end of range | $ 4 |
Expected remediation costs for each of the next four years, high end of range | 18 |
Environmental remediation costs | $ 4 | $ 2
Material sites |  |
Schedule Of Commitments And Contingencies [Line Items] |  |
Identified material sites for environmental remediation (in number of sites) | site | 20 |
Minimum liability for environmental remediation | $ 142 |
Immaterial sites |  |
Schedule Of Commitments And Contingencies [Line Items] |  |
Immaterial sites for environmental remediation (in number of sites) | site | 16 |
Immaterial sites | Minimum |  |
Schedule Of Commitments And Contingencies [Line Items] |  |
Minimum liability for environmental remediation | $ 4 |
San Onofre |  |
Schedule Of Commitments And Contingencies [Line Items] |  |
Minimum liability for environmental remediation | $ 92 |

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
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