Fair Value Measurements (Fair Value by Level) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Assets at Fair Value
Nuclear decommissioning trusts	$ 4,741			$ 4,494
Liabilities at Fair Value
Money market funds	40			68
Southern California Edison
Assets at Fair Value
Nuclear decommissioning trusts	4,741		4,740	4,494		4,332	4,182	4,048
Liabilities at Fair Value
Percentage of equity investments located in the United States (as a percent)	69.00%			70.00%
Collateralized mortgage obligations and other asset backed securities	58			47
Receivables (payables) net related to investments	5			12
Money market funds	8			8
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Derivative contracts	0			0
Other	35			39
Nuclear decommissioning trusts	3,379	[1]		3,380	[1]
Total assets	3,414			3,419
Liabilities at Fair Value
Derivative contracts	0			0
Total liabilities	0			0
Net assets (liabilities)	3,414			3,419
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	1,970	[2]		2,208	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Fixed income
Assets at Fair Value
Nuclear decommissioning trusts	744	[3]		841	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	665			331
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at Fair Value
Derivative contracts	5			11
Other	0			0
Nuclear decommissioning trusts	1,357	[1]		1,102	[1]
Total assets	1,362			1,113
Liabilities at Fair Value
Derivative contracts	6			37
Total liabilities	6			37
Net assets (liabilities)	1,356			1,076
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]		0	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Fixed income
Assets at Fair Value
Nuclear decommissioning trusts	1,336	[3]		1,102	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	21			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at Fair Value
Derivative contracts	343			372
Other	0			0
Nuclear decommissioning trusts	0	[1]		0	[1]
Total assets	343			372
Liabilities at Fair Value
Derivative contracts	1,101			1,177
Total liabilities	1,101			1,177
Net assets (liabilities)	(758)			(805)
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]		0	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Fixed income
Assets at Fair Value
Nuclear decommissioning trusts	0	[3]		0	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral
Assets at Fair Value
Derivative contracts	0	[4]		(10)	[4]
Other	0	[4]		0	[4]
Nuclear decommissioning trusts	0	[1],[4]		0	[1],[4]
Total assets	0	[4]		(10)	[4]
Liabilities at Fair Value
Derivative contracts	(6)	[4]		(20)	[4]
Total liabilities	(6)	[4]		(20)	[4]
Net assets (liabilities)	6	[4]		10	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[2],[4]		0	[2],[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Fixed income
Assets at Fair Value
Nuclear decommissioning trusts	0	[3],[4]		0	[3],[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]		0	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Total
Assets at Fair Value
Derivative contracts	348			373
Other	35			39
Nuclear decommissioning trusts	4,736	[1]		4,482	[1]
Total assets	5,119			4,894
Liabilities at Fair Value
Derivative contracts	1,101			1,194
Total liabilities	1,101			1,194
Net assets (liabilities)	4,018			3,700
Southern California Edison | Fair Value, Measurements, Recurring | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	1,970	[2]		2,208	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Total | Fixed income
Assets at Fair Value
Nuclear decommissioning trusts	2,080	[3]		1,943	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	$ 686			$ 331

[1] Excludes net receivables of $5 million and net receivables of $12 million at September 30, 2014 and December 31, 2013, respectively, of interest and dividend receivables as well as receivables and payables related to SCE's pending securities sales and purchases.

[2] Approximately 69% and 70% of SCE's equity investments were located in the United States at September 30, 2014 and December 31, 2013, respectively.

[3] At September 30, 2014 and December 31, 2013, SCE's corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $58 million and $47 million, respectively.

[4] Represents the netting of assets and liabilities under master netting agreements and cash collateral across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.