Fair Value Measurements (Fair Value by Level) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014	Dec. 31, 2013
Assets at fair value
Nuclear decommissioning trusts	$ 4,896		$ 4,799
Liabilities at fair value
Money market funds	35		35
Southern California Edison
Assets at fair value
Nuclear decommissioning trusts	4,896		4,799		4,587	4,494
Liabilities at fair value
Percentage of equity investments located in the United States (as a percent)	72.00%		73.00%
Collateralized mortgage obligations and other asset backed securities	161		49
Receivables (payables) net related to investments	2		(57)
Money market funds	5		5
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at fair value
Derivative contracts	0		0
Other	34		33
Nuclear decommissioning trusts	3,145	[1]	3,340	[1]
Total assets	3,179		3,373
Liabilities at fair value
Derivative contracts	0		0
Total liabilities	0		0
Net assets (liabilities)	3,179		3,373
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at fair value
Nuclear decommissioning trusts	2,074	[2]	2,031	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Fixed income
Assets at fair value
Nuclear decommissioning trusts	1,027	[3]	703	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	44		606
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at fair value
Derivative contracts	0		0
Other	0		0
Nuclear decommissioning trusts	1,749	[1]	1,516	[1]
Total assets	1,749		1,516
Liabilities at fair value
Derivative contracts	81		86
Total liabilities	81		86
Net assets (liabilities)	1,668		1,430
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	1,651	[3]	1,350	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	98		166
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at fair value
Derivative contracts	306		321
Other	0		0
Nuclear decommissioning trusts	0	[1]	0	[1]
Total assets	306		321
Liabilities at fair value
Derivative contracts	1,282		1,223
Total liabilities	1,282		1,223
Net assets (liabilities)	(976)		(902)
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]	0	[4]
Other	0	[4]	0	[4]
Nuclear decommissioning trusts	0	[1],[4]	0	[1],[4]
Total assets	0	[4]	0	[4]
Liabilities at fair value
Derivative contracts	(71)	[4]	(61)	[4]
Total liabilities	(71)	[4]	(61)	[4]
Net assets (liabilities)	71	[4]	61	[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	306		321
Other	34		33
Nuclear decommissioning trusts	4,894	[1]	4,856	[1]
Total assets	5,234		5,210
Liabilities at fair value
Derivative contracts	1,292		1,248
Total liabilities	1,292		1,248
Net assets (liabilities)	3,942		3,962
Southern California Edison | Fair Value, Measurements, Recurring | Total | Stocks
Assets at fair value
Nuclear decommissioning trusts	2,074	[2]	2,031	[2]
Southern California Edison | Fair Value, Measurements, Recurring | Total | Fixed income
Assets at fair value
Nuclear decommissioning trusts	2,678	[3]	2,053	[3]
Southern California Edison | Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	$ 142		$ 772

[1] Excludes net receivables of $2 million and net payables of $57 million at March 31, 2015 and December 31, 2014, which consist of interest and dividend receivables as well as receivables and payables related to SCE's pending securities sales and purchases.

[2] Approximately 72% and 73% of SCE's equity investments were located in the United States at March 31, 2015 and December 31, 2014, respectively.

[3] Includes corporate bonds, which were diversified and included collateralized mortgage obligations and other asset backed securities of $161 million and $49 million at March 31, 2015 and December 31, 2014, 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.