Regulatory Assets and Liabilities (Regulatory Balancing Accounts) (Details) - SCE - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Regulatory balancing accounts | Energy resource recovery account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	$ (20)	$ (439)
Regulatory balancing accounts | New system generation balancing account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(6)	(171)
Refunds of excess revenue | Significant components
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(1,715)	(2,002)
Refunds of excess revenue | Public purpose programs and energy efficiency programs
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(992)	(683)
Refunds of excess revenue | Base revenue requirement balancing account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(426)	(319)
Refunds of excess revenue | Tax accounting memorandum account and pole loading
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(142)	(248)
Refunds of excess revenue | Department of Energy litigation memorandum account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(122)	0
Refunds of excess revenue | Greenhouse gas auction revenue
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	31	(75)
Refunds of excess revenue | FERC balancing accounts
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(69)	74
Refunds of excess revenue | Other
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	$ 31	$ (141)