Fair Value Measurements (Fair Value by Level) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2012		Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Assets at Fair Value
Money market funds	$ 72			$ 107
Nuclear decommissioning trusts	4,181			4,048
Liabilities at Fair Value
Receivables (payables) net related to investments	(148)			(1)
Level 3
Assets at Fair Value
Total assets	162			221
Liabilities at Fair Value
Total liabilities	1,129			1,012
Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Money market funds	10
Southern California Edison
Assets at Fair Value
Money market funds	10			5
Nuclear decommissioning trusts	4,181		4,246	4,048		3,810	3,853	3,592
Liabilities at Fair Value
Percentage of equity investments located in the United States (as a percent)	70.00%					66.00%
Collateralized mortgage obligations and other asset backed securities	58					56
Receivables (payables) net related to investments	(148)					(1)
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Money market funds				5
Alternative Investments, Fair Value Disclosure	28
Derivative contracts	0			0
Long-term disability plan	8			8
Nuclear decommissioning trusts	3,134			2,869
Total assets	3,180			2,882
Liabilities at Fair Value
Derivative contracts	0			0
Total liabilities	0			0
Net assets (liabilities)	3,180			2,882
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Congestion Revenue Rights
Assets at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Electricity
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Natural Gas
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Tolling
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,085	[1]		2,271	[1]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	881			477
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]		0	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	168	[3]		121	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at Fair Value
Money market funds	0			0
Alternative Investments, Fair Value Disclosure	0
Derivative contracts	13			8
Long-term disability plan	0			0
Nuclear decommissioning trusts	1,195			1,180
Total assets	1,208			1,188
Liabilities at Fair Value
Derivative contracts	70			115
Total liabilities	70			115
Net assets (liabilities)	1,138			1,073
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Congestion Revenue Rights
Assets at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Electricity
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	2			2
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Natural Gas
Assets at Fair Value
Derivative contracts	13			8
Liabilities at Fair Value
Derivative contracts	68			113
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Tolling
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1]		0	[1]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	144			126
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	592			644
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	347	[2]		410	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	112	[3]		0	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at Fair Value
Money market funds	0			0
Alternative Investments, Fair Value Disclosure	0
Derivative contracts	162			221
Long-term disability plan	0			0
Nuclear decommissioning trusts	0			0
Total assets	162			221
Liabilities at Fair Value
Derivative contracts	1,129			1,012
Total liabilities	1,129			1,012
Net assets (liabilities)	(967)			(791)
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Congestion Revenue Rights
Assets at Fair Value
Derivative contracts	137			186
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Electricity
Assets at Fair Value
Derivative contracts	17			31
Liabilities at Fair Value
Derivative contracts	6			5
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Natural Gas
Assets at Fair Value
Derivative contracts	0			0
Liabilities at Fair Value
Derivative contracts	0			2
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Tolling
Assets at Fair Value
Derivative contracts	8			4
Liabilities at Fair Value
Derivative contracts	1,123			1,005
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1]		0	[1]
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0			0
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2]		0	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[3]		0	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral
Assets at Fair Value
Money market funds	0	[4]		0	[4]
Alternative Investments, Fair Value Disclosure	0
Derivative contracts	(11)	[4]		(15)	[4]
Long-term disability plan	0	[4]		0	[4]
Nuclear decommissioning trusts	0	[4]		0	[4]
Total assets	(11)	[4]		(15)	[4]
Liabilities at Fair Value
Derivative contracts	(32)	[4]		(62)	[4]
Total liabilities	(32)	[4]		(62)	[4]
Net assets (liabilities)	21	[4]		47	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Congestion Revenue Rights
Assets at Fair Value
Derivative contracts	0	[4]		0	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Electricity
Assets at Fair Value
Derivative contracts	(10)	[4]		(13)	[4]
Liabilities at Fair Value
Derivative contracts	(1)	[4]		(2)	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Natural Gas
Assets at Fair Value
Derivative contracts	(1)	[4]		(2)	[4]
Liabilities at Fair Value
Derivative contracts	(31)	[4]		(60)	[4]
Southern California Edison | 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]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[1],[4]		0	[1],[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]		0	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[4]		0	[4]
Southern California Edison | Fair Value, Measurements, Recurring | Netting and Collateral | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[2],[4]		0	[2],[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	[3],[4]		0	[3],[4]
Southern California Edison | Fair Value, Measurements, Recurring | Total
Assets at Fair Value
Money market funds	10			5
Alternative Investments, Fair Value Disclosure	28
Derivative contracts	164			214
Long-term disability plan	8			8
Nuclear decommissioning trusts	4,329			4,049
Total assets	4,539			4,276
Liabilities at Fair Value
Derivative contracts	1,167			1,065
Total liabilities	1,167			1,065
Net assets (liabilities)	3,372			3,211
Southern California Edison | Fair Value, Measurements, Recurring | Total | Congestion Revenue Rights
Assets at Fair Value
Derivative contracts	137			186
Southern California Edison | Fair Value, Measurements, Recurring | Total | Electricity
Assets at Fair Value
Derivative contracts	7			18
Liabilities at Fair Value
Derivative contracts	7			5
Southern California Edison | Fair Value, Measurements, Recurring | Total | Natural Gas
Assets at Fair Value
Derivative contracts	12			6
Liabilities at Fair Value
Derivative contracts	37			55
Southern California Edison | Fair Value, Measurements, Recurring | Total | Tolling
Assets at Fair Value
Derivative contracts	8			4
Liabilities at Fair Value
Derivative contracts	1,123			1,005
Southern California Edison | Fair Value, Measurements, Recurring | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,085	[1]		2,271	[1]
Southern California Edison | Fair Value, Measurements, Recurring | Total | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	1,025			603
Southern California Edison | Fair Value, Measurements, Recurring | Total | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	592			644
Southern California Edison | Fair Value, Measurements, Recurring | Total | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	347	[2]		410	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	$ 280	[3]		$ 121	[3]

[1] Approximately 70% and 66% of SCE's equity investments were located in the United States at June 30, 2013 and December 31, 2012, respectively.

[2] At June 30, 2013 and December 31, 2012, SCE's corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $58 million and $56 million, respectively.

[3] Excludes net payables of $148 million and $1 million at June 30, 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.