Derivative Instruments (Balance Sheet Disclosures) (Details) - Southern California Edison Company - Commodity derivative contracts - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Other current liabilities
Net Asset
Collateral received	$ 1	$ 2
Electric Utility
Derivative Assets
Gross amounts recognized	39	75
Gross amounts offset in the consolidated balance sheets	(1)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	38	74
Derivative Liabilities
Gross amounts recognized	4	1,158
Gross amounts offset in the consolidated balance sheets	(1)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	3	1,157
Net Asset
Gross amounts recognized	35	1,083
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	35	1,083
Electric Utility | Derivative Assets, Short-Term
Derivative Assets
Gross amounts recognized	37	74
Gross amounts offset in the consolidated balance sheets	(1)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	36	73
Electric Utility | Derivative Assets, Long-Term
Derivative Assets
Gross amounts recognized	2	1
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	2	1
Electric Utility | Derivative Liability, Short-Term
Derivative Liabilities
Gross amounts recognized	4	217
Gross amounts offset in the consolidated balance sheets	(1)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	3	216
Electric Utility | Derivative Liability, Long-Term
Derivative Liabilities
Gross amounts recognized	0	941
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	0	$ 941
Electric Utility | Derivative liabilities
Derivative Liabilities
Gross amounts recognized	$ (1,000)