Regulatory Assets and Liabilities (Schedule of Net Regulatory Balancing Accounts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
IRS | Tax accounting method changes
Regulatory Assets and Liabilities
Incremental tax benefits related to repair deductions, before tax	$ 118
Regulatory balancing accounts | Energy resource recovery account
Regulatory Assets and Liabilities
Asset (liability)	190	$ (20)
Regulatory balancing accounts | New system generation balancing account
Regulatory Assets and Liabilities
Asset (liability)	(99)	(6)
Refunds of excess revenue | Net regulatory balancing accounts
Regulatory Assets and Liabilities
Asset (liability)	(2,230)	(1,715)
Refunds of excess revenue | Public purpose programs and energy efficiency programs
Regulatory Assets and Liabilities
Asset (liability)	(1,178)	(992)
Refunds of excess revenue | Tax accounting memorandum account and pole loading balancing account
Regulatory Assets and Liabilities
Asset (liability)	(461)	(142)
Refunds of excess revenue | Base rate recovery balancing account
Regulatory Assets and Liabilities
Asset (liability)	(265)	(426)
Refunds of excess revenue | Department of Energy litigation memorandum account
Regulatory Assets and Liabilities
Asset (liability)	(156)	(122)
Refunds of excess revenue | Greenhouse gas auction revenue
Regulatory Assets and Liabilities
Asset (liability)	(63)	31
Refunds of excess revenue | FERC balancing accounts
Regulatory Assets and Liabilities
Asset (liability)	(209)	(69)
Refunds of excess revenue | Other
Regulatory Assets and Liabilities
Asset (liability)	$ 11	$ 31