Summary of Significant Accounting Policies (Goodwill) (Details) $ in Millions	Sep. 30, 2018 USD ($)
Edison Energy
Goodwill [Line Items]
Goodwill	$ 78
Edison Energy
Goodwill [Line Items]
Investment	$ 104

Amount of Equity in net profit and loss for the period. Give totals for each group. If operations of any controlled companies are different in character from those of the company, group such affiliates (1) within divisions and (2) by type of activities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(Column C))
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(2))
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(6))
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant