Summary of Significant Accounting Policies (Changes in Allowance for Uncollectible Accounts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 75	$ 35
Included in operation and maintenance expenses	11	39
Deferred to regulatory assets	43	64
Less: write-offs, net of recoveries	5	14
Ending balance	124	124
All others
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	15	14
Included in operation and maintenance expenses	4	11
Deferred to regulatory assets	0	0
Less: write-offs, net of recoveries	2	8
Ending balance	$ 17	$ 17