Fair Value Measurements (Fair Value by Level) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Assets at Fair Value
Money market funds	$ 107		$ 114
Nuclear decommissioning trusts	4,048		3,592
Level 3
Assets at Fair Value
Total assets	221
Liabilities at Fair Value
Total liabilities	1,012
Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Money market funds	5		21
Derivative contracts	0		0
Long-term disability plan	8		8
Nuclear decommissioning trusts	2,869		2,332
Total assets	2,882		2,361
Liabilities at Fair Value
Derivative contracts	0		0
Total liabilities	0		0
Net assets (liabilities)	2,882		2,361
Fair Value, Measurements, Recurring | Level 1 | CRRs
Assets at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 1 | Electricity
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 1 | Natural Gas
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 1 | Tolling
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,271	[1]	1,899	[1]
Fair Value, Measurements, Recurring | Level 1 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0		0
Fair Value, Measurements, Recurring | Level 1 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	477		433
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]	0	[2]
Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	121	[3]	0	[3]
Fair Value, Measurements, Recurring | Level 2
Assets at Fair Value
Money market funds	0		0
Derivative contracts	8		5
Long-term disability plan	0		0
Nuclear decommissioning trusts	1,180		1,235
Total assets	1,188		1,240
Liabilities at Fair Value
Derivative contracts	115		239
Total liabilities	115		239
Net assets (liabilities)	1,073		1,001
Fair Value, Measurements, Recurring | Level 2 | CRRs
Assets at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 2 | Electricity
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	2		5
Fair Value, Measurements, Recurring | Level 2 | Natural Gas
Assets at Fair Value
Derivative contracts	8		5
Liabilities at Fair Value
Derivative contracts	113		234
Fair Value, Measurements, Recurring | Level 2 | Tolling
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	0		0
Fair Value, Measurements, Recurring | Level 2 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1]	0	[1]
Fair Value, Measurements, Recurring | Level 2 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	644		756
Fair Value, Measurements, Recurring | Level 2 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	126		147
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	410	[2]	317	[2]
Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[3]	15	[3]
Fair Value, Measurements, Recurring | Level 3
Assets at Fair Value
Money market funds	0		0
Derivative contracts	221		133
Long-term disability plan	0		0
Nuclear decommissioning trusts	0		0
Total assets	221		133
Liabilities at Fair Value
Derivative contracts	1,012		887
Total liabilities	1,012		887
Net assets (liabilities)	(791)		(754)
Fair Value, Measurements, Recurring | Level 3 | CRRs
Assets at Fair Value
Derivative contracts	186		122
Fair Value, Measurements, Recurring | Level 3 | Electricity
Assets at Fair Value
Derivative contracts	31		1
Liabilities at Fair Value
Derivative contracts	5		65
Fair Value, Measurements, Recurring | Level 3 | Natural Gas
Assets at Fair Value
Derivative contracts	0		0
Liabilities at Fair Value
Derivative contracts	2		23
Fair Value, Measurements, Recurring | Level 3 | Tolling
Assets at Fair Value
Derivative contracts	4		10
Liabilities at Fair Value
Derivative contracts	1,005		799
Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1]	0	[1]
Fair Value, Measurements, Recurring | Level 3 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0		0
Fair Value, Measurements, Recurring | Level 3 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0		0
Fair Value, Measurements, Recurring | Level 3 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]	0	[2]
Fair Value, Measurements, Recurring | Level 3 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[3]	0	[3]
Fair Value, Measurements, Recurring | Netting and Collateral
Assets at Fair Value
Money market funds	0	[4]	0	[4]
Derivative contracts	(15)	[4]	(3)	[4]
Long-term disability plan	0	[4]	0	[4]
Nuclear decommissioning trusts	0	[4]	0	[4]
Total assets	(15)	[4]	(3)	[4]
Liabilities at Fair Value
Derivative contracts	(62)	[4]	(55)	[4]
Total liabilities	(62)	[4]	(55)	[4]
Net assets (liabilities)	47	[4]	52	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | CRRs
Assets at Fair Value
Derivative contracts	0	[4]	0	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Electricity
Assets at Fair Value
Derivative contracts	(13)	[4]	0	[4]
Liabilities at Fair Value
Derivative contracts	(2)	[4]	(2)	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Natural Gas
Assets at Fair Value
Derivative contracts	(2)	[4]	(3)	[4]
Liabilities at Fair Value
Derivative contracts	(60)	[4]	(53)	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Tolling
Assets at Fair Value
Derivative contracts	0	[4]	0	[4]
Liabilities at Fair Value
Derivative contracts	0	[4]	0	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1],[4]	0	[1],[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]	0	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]	0	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2],[4]	0	[2],[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[3],[4]	0	[3],[4]
Fair Value, Measurements, Recurring | Total
Assets at Fair Value
Money market funds	5		21
Derivative contracts	214		135
Long-term disability plan	8		8
Nuclear decommissioning trusts	4,049		3,567
Total assets	4,276		3,731
Liabilities at Fair Value
Derivative contracts	1,065		1,071
Total liabilities	1,065		1,071
Net assets (liabilities)	3,211		2,660
Fair Value, Measurements, Recurring | Total | CRRs
Assets at Fair Value
Derivative contracts	186		122
Fair Value, Measurements, Recurring | Total | Electricity
Assets at Fair Value
Derivative contracts	18		1
Liabilities at Fair Value
Derivative contracts	5		68
Fair Value, Measurements, Recurring | Total | Natural Gas
Assets at Fair Value
Derivative contracts	6		2
Liabilities at Fair Value
Derivative contracts	55		204
Fair Value, Measurements, Recurring | Total | Tolling
Assets at Fair Value
Derivative contracts	4		10
Liabilities at Fair Value
Derivative contracts	1,005		799
Fair Value, Measurements, Recurring | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,271	[1]	1,899	[1]
Fair Value, Measurements, Recurring | Total | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	644		756
Fair Value, Measurements, Recurring | Total | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	603		580
Fair Value, Measurements, Recurring | Total | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	410	[2]	317	[2]
Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	121	[3]	15	[3]
Southern California Edison
Assets at Fair Value
Money market funds	5		21
Nuclear decommissioning trusts	4,048		3,592		3,480	3,140
Liabilities at Fair Value
Percentage of equity investments located in the United States (as a percent)	66.00%		70.00%
Collateralized mortgage obligations and other asset backed securities	56		22
Receivables (payables) net related to investments	(1)		25
Southern California Edison | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,271		1,899
Southern California Edison | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	644		756
Southern California Edison | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	603		580
Southern California Edison | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	$ 410		$ 317

[1] Approximately 66% and 70% of SCE's equity investments were located in the United States at December 31, 2012 and 2011, respectively.

[2] At December 31, 2012 and 2011, SCE's corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $56 million and $22 million, respectively.

[3] Excludes net payables of $1 million at December 31, 2012 ;and net receivables of $25 million at December 31, 2011, of interest and dividend receivables as well as receivables and payables related to SCE's pending securities sales and purchases.

[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.