Summary of Significant Accounting Policies (Goodwill) (Details) - Edison Energy Group - USD ($)	3 Months Ended
Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Goodwill [Line Items]
Goodwill impairment	$ 34,000,000	$ 25,000,000	$ 19,000,000
Goodwill impairment after-tax	$ 25,000,000	18,000,000	$ 13,000,000
Goodwill		$ 34,000,000		$ 0

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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