Investments (Amortized Cost and Fair Value of Nuclear Decommissioning Trusts) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Nuclear Decommissioning Trusts Disclosures
Fair Value	$ 4,334	$ 4,440
Southern California Edison
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	2,583	2,803
Fair Value	4,334	4,440
Fair Value, Measurements, Recurring \| Southern California Edison
Nuclear Decommissioning Trusts Disclosures
Fair Value	4,402	4,499
Fair Value, Measurements, Recurring \| Southern California Edison \| Stocks
Nuclear Decommissioning Trusts Disclosures
Amortized Cost		236
Fair Value	1,520	1,596
Fair Value, Measurements, Recurring \| Southern California Edison \| Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	636	643
Fair Value	740	768
Fair Value, Measurements, Recurring \| Southern California Edison \| U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	1,259	1,235
Fair Value	1,331	1,319
Fair Value, Measurements, Recurring \| Southern California Edison \| Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	593	579
Fair Value	644	643
Fair Value, Measurements, Recurring \| Southern California Edison \| Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	95	110
Fair Value	99	114
Repurchase agreements payable	$ 37	$ 29

The amount of decommissioning trust assets at amortized cost as of the balance sheet date.

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- References

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- Definition

The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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- Definition

The carrying value of securities purchased to be resold in reverse repurchase transactions as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(2)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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