Regulatory Assets and Liabilities (Schedule of Regulatory Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Current regulatory liabilities	$ 1,347	$ 1,121
Long-term regulatory liabilities	8,683	8,614
Southern California Edison
Regulatory Liabilities [Line Items]
Current regulatory liabilities	1,347	1,121
Long-term regulatory liabilities	8,683	8,614
Total regulatory liabilities	10,030	9,735
Southern California Edison | Regulatory balancing accounts
Regulatory Liabilities [Line Items]
Current regulatory liabilities	1,124	1,009
Long-term regulatory liabilities	1,482	1,316
Southern California Edison | Energy derivatives
Regulatory Liabilities [Line Items]
Current regulatory liabilities	61	74
Southern California Edison | San Onofre
Regulatory Liabilities [Line Items]
Current regulatory liabilities	47	5
Long-term regulatory liabilities	26	26
Southern California Edison | Other
Regulatory Liabilities [Line Items]
Current regulatory liabilities	115	33
Long-term regulatory liabilities	73	64
Southern California Edison | Costs of removal
Regulatory Liabilities [Line Items]
Long-term regulatory liabilities	2,772	2,741
Southern California Edison | Re-measurement Of Deferred Taxes [Member]
Regulatory Liabilities [Line Items]
Long-term regulatory liabilities	2,834	2,892
Southern California Edison | Recoveries in excess of ARO liabilities
Regulatory Liabilities [Line Items]
Long-term regulatory liabilities	$ 1,496	$ 1,575