Summary of Significant Accounting Policies (Uncollectible Allowance) (Details) - SCE - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 175	$ 35
Included in operation and maintenance expenses	6	16
Deferred to regulatory assets	34
Less: write-offs, net of recoveries	5	4
Ending balance	210	47
All others
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13	14
Included in operation and maintenance expenses	4	2
Deferred to regulatory assets		0
Less: write-offs, net of recoveries	1	3
Ending balance	$ 16	$ 13