Regulatory Assets and Liabilities (Regulatory Balancing Accounts) (Details) - SCE - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory balancing accounts | Energy resource recovery account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	$ (89)	$ (23)
Regulatory balancing accounts | Portfolio allocation balancing account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	497	537
Regulatory balancing accounts | New system generation balancing account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	(10)	85
Revenue subject to refund | Significant components
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	1,388	(365)
Revenue subject to refund | Public purpose programs and energy efficiency programs
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	(1,130)	(1,244)
Revenue subject to refund | Base revenue requirement balancing account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	622	(328)
Revenue subject to refund | Greenhouse gas auction revenue and low carbon fuel standard revenue
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	(125)	(196)
Revenue subject to refund | FERC balancing accounts
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	12	(127)
Revenue subject to refund | Wildfire and drought restoration account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	361	120
Revenue subject to refund | Wildfire expense memorandum account
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	1,104	748
Revenue subject to refund | COVID-19-related memorandum accounts
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	176	0
Revenue subject to refund | Other
Regulatory Assets and Liabilities
Net regulatory assets (liabilities) pertaining to balancing accounts	$ (30)	$ 63