Fair Value Measurements (Fair Value by Level) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Assets at Fair Value
Money market funds	$ 58		$ 107		$ 107
Nuclear decommissioning trusts	4,246		4,048
Level 3
Assets at Fair Value
Total assets	203		221
Liabilities at Fair Value
Total liabilities	1,085		1,012
Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Money market funds	5		5
Derivative contracts	0		0
Long-term disability plan	8		8
Nuclear decommissioning trusts	3,120		2,869
Total assets	3,133		2,882
Liabilities at Fair Value
Derivative contracts	0		0
Total liabilities	0		0
Net assets (liabilities)	3,133		2,882
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
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	2,468	[1]	2,271	[1]
Fair Value, Measurements, Recurring | Level 1 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	571		477
Fair Value, Measurements, Recurring | Level 1 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0		0
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	81	[3]	121	[3]
Fair Value, Measurements, Recurring | Level 2
Assets at Fair Value
Money market funds	0		0
Derivative contracts	3		8
Long-term disability plan	0		0
Nuclear decommissioning trusts	1,114		1,180
Total assets	1,117		1,188
Liabilities at Fair Value
Derivative contracts	77		115
Total liabilities	77		115
Net assets (liabilities)	1,040		1,073
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	3		0
Liabilities at Fair Value
Derivative contracts	0		2
Fair Value, Measurements, Recurring | Level 2 | Natural Gas
Assets at Fair Value
Derivative contracts			8
Liabilities at Fair Value
Derivative contracts	77		113
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 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	75		126
Fair Value, Measurements, Recurring | Level 2 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	631		644
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	408	[2]	410	[2]
Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[3]	0	[3]
Fair Value, Measurements, Recurring | Level 3
Assets at Fair Value
Money market funds	0		0
Derivative contracts	203		221
Long-term disability plan	0		0
Nuclear decommissioning trusts	0		0
Total assets	203		221
Liabilities at Fair Value
Derivative contracts	1,085		1,012
Total liabilities	1,085		1,012
Net assets (liabilities)	(882)		(791)
Fair Value, Measurements, Recurring | Level 3 | CRRs
Assets at Fair Value
Derivative contracts	170		186
Fair Value, Measurements, Recurring | Level 3 | Electricity
Assets at Fair Value
Derivative contracts	29		31
Liabilities at Fair Value
Derivative contracts	1		5
Fair Value, Measurements, Recurring | Level 3 | Natural Gas
Assets at Fair Value
Derivative contracts			0
Liabilities at Fair Value
Derivative contracts	0		2
Fair Value, Measurements, Recurring | Level 3 | Tolling
Assets at Fair Value
Derivative contracts	4		4
Liabilities at Fair Value
Derivative contracts	1,084		1,005
Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1]	0	[1]
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 | Municipal bonds
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	(14)	[4]	(15)	[4]
Long-term disability plan	0	[4]	0	[4]
Nuclear decommissioning trusts	0	[4]	0	[4]
Total assets	(14)	[4]	(15)	[4]
Liabilities at Fair Value
Derivative contracts	(41)	[4]	(62)	[4]
Total liabilities	(41)	[4]	(62)	[4]
Net assets (liabilities)	27	[4]	47	[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	(14)	[4]	(13)	[4]
Liabilities at Fair Value
Derivative contracts	0	[4]	(2)	[4]
Fair Value, Measurements, Recurring | Netting and Collateral | Natural Gas
Assets at Fair Value
Derivative contracts			(2)	[4]
Liabilities at Fair Value
Derivative contracts	(41)	[4]	(60)	[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 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]	0	[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 | 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		5
Derivative contracts	192		214
Long-term disability plan	8		8
Nuclear decommissioning trusts	4,234		4,049
Total assets	4,439		4,276
Liabilities at Fair Value
Derivative contracts	1,121		1,065
Total liabilities	1,121		1,065
Net assets (liabilities)	3,318		3,211
Fair Value, Measurements, Recurring | Total | CRRs
Assets at Fair Value
Derivative contracts	170		186
Fair Value, Measurements, Recurring | Total | Electricity
Assets at Fair Value
Derivative contracts	18		18
Liabilities at Fair Value
Derivative contracts	1		5
Fair Value, Measurements, Recurring | Total | Natural Gas
Assets at Fair Value
Derivative contracts			6
Liabilities at Fair Value
Derivative contracts	36		55
Fair Value, Measurements, Recurring | Total | Tolling
Assets at Fair Value
Derivative contracts	4		4
Liabilities at Fair Value
Derivative contracts	1,084		1,005
Fair Value, Measurements, Recurring | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,468	[1]	2,271	[1]
Fair Value, Measurements, Recurring | Total | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	646		603
Fair Value, Measurements, Recurring | Total | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	631		644
Fair Value, Measurements, Recurring | Total | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	408	[2]	410	[2]
Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	81	[3]	121	[3]
Southern California Edison
Assets at Fair Value
Money market funds	5				5
Nuclear decommissioning trusts	4,246		4,048		3,853	3,592
Liabilities at Fair Value
Percentage of equity investments located in the United States (as a percent)	67.00%				66.00%
Collateralized mortgage obligations and other asset backed securities	62				56
Receivables (payables) net related to investments	12				(1)
Southern California Edison | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,468		2,271
Southern California Edison | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	646		603
Southern California Edison | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	631		644
Southern California Edison | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	$ 408		$ 410

[1] Approximately 67% and 66% of SCE's equity investments were located in the United States at March 31, 2013 and December 31, 2012, respectively.

[2] At March 31, 2013 and December 31, 2012, SCE's corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $62 million and $56 million, respectively.

[3] Excludes net receivables of $12 million and net payables of $1 million at March 31, 2013 and December 31, 2012, respectively, 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.