Summary of Significant Accounting Policies (Changes in Allowance for Uncollectible Accounts) (Details) - SCE $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 35
Included in operation and maintenance expenses	36
Deferred to regulatory assets	120
Less: write-offs, net of recoveries	16
Ending balance	175
All others
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	14
Included in operation and maintenance expenses	9
Deferred to regulatory assets	0
Less: write-offs, net of recoveries	10
Ending balance	$ 13