Summary of Significant Accounting Policies - (Changes in Allowance for Uncollectible Accounts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 47	$ 35
Included in operation and maintenance expenses	12	28
Deferred to regulatory assets	21	21
Less: write-offs, net of recoveries	5	9
Ending balance	75	75
All others
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13	14
Included in operation and maintenance expenses	5	7
Deferred to regulatory assets	0	0
Less: write-offs, net of recoveries	3	6
Ending balance	$ 15	$ 15