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Summary of Significant Accounting Policies (Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2017
SoCore Energy
Goodwill [Line Items]
Goodwill impairment			$ 17
Goodwill impairment after-tax			$ 10
Edison Energy Group
Goodwill [Line Items]
Goodwill impairment	$ 25	$ 19
Goodwill impairment after-tax	18	13
Goodwill	34	$ 59
Edison Energy
Goodwill [Line Items]
Investment	$ 57