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Regulatory Assets and Liabilities (Schedule of Regulatory Assets) (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
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Regulatory Assets [Line Items] |  |
Current regulatory assets | $ 678 | $ 703
Long-term regulatory assets | 4,932 | 4,914
Southern California Edison |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 678 | 703
Long-term regulatory assets | 4,932 | 4,914
Total regulatory assets | 5,610 | 5,617
Southern California Edison | Regulatory balancing accounts |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 459 | 484
Long-term regulatory assets | 160 | 143
Southern California Edison | Power contracts and energy derivatives |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 203 | 203
Long-term regulatory assets | 774 | 799
Southern California Edison | Other |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 16 | 16
Long-term regulatory assets | 36 | 51
Southern California Edison | Deferred income taxes, net of liabilities |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | 3,202 | 3,143
Southern California Edison | Pensions and other postretirement benefits |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | 268 | 271
Southern California Edison | Unamortized investments, net of accumulated amortization |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | 116 | 123
Southern California Edison | San Onofre |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | 72 | 72
Southern California Edison | Unamortized loss on reacquired debt |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | 164 | 168
Southern California Edison | Environmental remediation |  |
Regulatory Assets [Line Items] |  |
Long-term regulatory assets | $ 140 | $ 144

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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