Derivative Instruments and Hedging Activities (Additional Disclosures) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Collateral provided to counterparties:
Offset against derivative liabilities	$ 54				$ 54				$ 53
Reflected in margin and collateral deposits	88				88				58
Collateral received from counterparties:
Offset against derivative assets	39				39				53
Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Unrealized derivative gains (losses) after taxes recorded in accumulated other comprehensive income	7		10		7		10
Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Unrealized derivative gains (losses) after taxes recorded in accumulated other comprehensive income	(79)		(49)		(79)		(49)
Cash flow hedges | Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Beginning of period derivative gains (losses)					35	[1]	43	[1]
Effective portion of changes in fair value					3	[1]	2	[1]
End of period derivative gains (losses)	7	[1]	16	[1]	7	[1]	16	[1]
Cash flow hedges | Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Beginning of period derivative gains (losses)					(90)	[1]	(16)	[1]
Effective portion of changes in fair value					(35)	[1]	(64)	[1]
End of period derivative gains (losses)	(125)	[1]	(80)	[1]	(125)	[1]	(80)	[1]
Cash flow hedges | Competitive power generation revenues | Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Reclassification to earnings					(31)	[1]	(29)	[1]
Cash flow hedges | Competitive power generation revenues | Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Reclassification to earnings					0	[1]	0	[1]
Cash flow hedges | Operating revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Amount of gains (losses) for cash flow hedge ineffectiveness	(2)		2
Economic hedges | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	8		(3)		25		5
Economic hedges | Fuel
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	3		(3)		2		1
Trading activities | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	22		11		72		68
Edison Mission Energy | Cash flow hedges | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Amount of gains (losses) for cash flow hedge ineffectiveness					0		2
Electric Utility | Southern California Edison | Economic hedges
Derivatives
Realized losses	(77)		(58)		(199)		(132)
Unrealized losses	(91)		(110)		(29)		(433)
Collateral already posted, fair value	0				0				0
Additional collateral, aggregate fair value	25				25
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Aggregate fair value of all derivative liabilities with credit-risk-related contingent features	$ 113				$ 113				$ 216

[1] Unrealized derivative gains (losses) are before income taxes. The after-tax amounts recorded in accumulated other comprehensive loss at September 30, 2012 and 2011 for commodity and interest rate contracts were $7 million and $(79) million, and $10 million and $(49) million, respectively.