Regulatory Assets and Liabilities (Regulatory Balancing Accounts) (Details) - Regulatory balancing accounts - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Energy resource recovery account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	$ (439)	$ 1,028
New system generation balancing account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(171)	35
Public purpose programs and energy efficiency programs
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(683)	(874)
Base rate recovery balancing account
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(319)	(5)
Greenhouse gas auction revenue
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(75)	(182)
FERC balancing accounts
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	74	(32)
Tax accounting memorandum account and pole loading
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(248)	0
Other
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(137)	(104)
Liability
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	(2,002)	(331)
Southern California Edison | Generator settlements
Regulatory Assets and Liabilities
Net Regulatory Assets Pertaining to Balancing Accounts	$ (4)	$ (197)