Derivative Instruments (Balance Sheet Disclosures) (Details) - Southern California Edison Company - Commodity derivative contracts - Electric Utility - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Assets
Gross amounts recognized	$ 87	$ 111
Gross amounts offset in the consolidated balance sheets	(8)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	79	110
Derivative Liabilities
Gross amounts recognized	28	3
Gross amounts offset in the consolidated balance sheets	(8)	(1)
Cash collateral posted	(12)	(1)
Net amounts presented in the consolidated balance sheets	8	1
Net Assets
Gross amounts recognized	59	108
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	12	1
Net amounts presented in the consolidated balance sheets	71	109
Derivative Assets, Short-Term
Derivative Assets
Gross amounts recognized	85	106
Gross amounts offset in the consolidated balance sheets	(8)	(1)
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	77	105
Derivative Assets, Long-Term
Derivative Assets
Gross amounts recognized	2	5
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	2	5
Derivative Liability, Short-Term
Derivative Liabilities
Gross amounts recognized	28	3
Gross amounts offset in the consolidated balance sheets	(8)	(1)
Cash collateral posted	(12)	(1)
Net amounts presented in the consolidated balance sheets	8	1
Derivative Liability, Long-Term
Derivative Liabilities
Gross amounts recognized	0	0
Gross amounts offset in the consolidated balance sheets	0	0
Cash collateral posted	0	0
Net amounts presented in the consolidated balance sheets	$ 0	$ 0

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