Regulatory Assets and Liabilities (Schedule of Net Regulatory Balancing and Memorandum Accounts) (Details) - Southern California Edison - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Regulatory balancing and memorandum accounts | Energy resource recovery account
Regulatory Assets and Liabilities
Asset (liability)	$ (264)	$ (23)
Regulatory balancing and memorandum accounts | Portfolio allocation balancing account
Regulatory Assets and Liabilities
Asset (liability)	684	537
Regulatory balancing and memorandum accounts | New system generation balancing account
Regulatory Assets and Liabilities
Asset (liability)	25	85
Refunds of excess revenue | Net regulatory balancing accounts
Regulatory Assets and Liabilities
Asset (liability)	657	(365)
Refunds of excess revenue | Public purpose programs and energy efficiency programs
Regulatory Assets and Liabilities
Asset (liability)	(1,221)	(1,244)
Refunds of excess revenue | Base revenue requirement balancing account
Regulatory Assets and Liabilities
Asset (liability)	420	(328)
Refunds of excess revenue | Greenhouse gas auction revenue and low carbon fuel standard revenue
Regulatory Assets and Liabilities
Asset (liability)	(104)	(196)
Refunds of excess revenue | FERC balancing accounts
Regulatory Assets and Liabilities
Asset (liability)	(33)	(127)
Refunds of excess revenue | Wildfire-related memorandum accounts
Regulatory Assets and Liabilities
Asset (liability)	1,061	868
Refunds of excess revenue | COVID 19-related memorandum accounts
Regulatory Assets and Liabilities
Asset (liability)	107	0
Refunds of excess revenue | Other
Regulatory Assets and Liabilities
Asset (liability)	$ (18)	$ 63