Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011		Dec. 31, 2010
Assets at Fair Value
Money market funds	$ 1,200				$ 1,300
Nuclear decommissioning trusts	3,853		3,619		3,592		3,480
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	38				22
Receivables (payables) net related to investments	(14)				25
Cash surrender value of life insurance	30				31
Total realized/unrealized gains (losses):
Unrealized gain (loss) related to Level 3 financial instruments reported within competitive power generation revenue	(7)		(6)
Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,124				1,899
Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	696				756
U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	642				580
Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	369				317
Level 3
Fair Value Disclosures Level 3
Fair value of net asset (liabilities) at beginning of period	(323)		97		97
Total realized/unrealized gains (losses):
Included in earnings	(15)	[1]	0	[1]
Included in regulatory assets and liabilities	(293)	[2],[3]	(134)	[2]
Included in accumulated other comprehensive income	2	[4]	1	[4]
Purchases	27		5
Settlements	(9)		(11)
Transfers out of Level 3	(51)	[5]	(2)	[5]
Fair value of net liabilities at end of period	(662)		(44)
Change during the period in unrealized losses related to assets and liabilities held at the end of the period	(295)	[6]	(139)	[6]
Fair Value, Measurements, Recurring | Level 1
Assets at Fair Value
Money market funds	1,222	[7]			1,321	[7]
Derivative contracts	13				8
Long-term disability plan	8				8
Nuclear decommissioning trusts	2,607				2,332
Total assets	3,850	[8]			3,669	[8]
Liabilities at Fair Value
Derivative contracts	0				0
Total liabilities	0				0
Net assets (liabilities)	3,850				3,669
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	6				4
Liabilities at Fair Value
Derivative contracts	0				0
Fair Value, Measurements, Recurring | Level 1 | Fuel Oil
Assets at Fair Value
Derivative contracts	7				4
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 | Interest rate contracts
Liabilities at Fair Value
Derivative contracts	0				0
Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,124	[9]			1,899	[9]
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	481				433
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[10]			0	[10]
Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	2	[11]			0	[11]
Fair Value, Measurements, Recurring | Level 2
Assets at Fair Value
Money market funds	0	[7]			0	[7]
Derivative contracts	148				71
Long-term disability plan	0				0
Nuclear decommissioning trusts	1,260				1,235
Total assets	1,408	[8]			1,306	[8]
Liabilities at Fair Value
Derivative contracts	271				247
Total liabilities	349				337
Net assets (liabilities)	1,059				969
Fair Value, Measurements, Recurring | Level 2 | Electricity
Assets at Fair Value
Derivative contracts	144				66
Liabilities at Fair Value
Derivative contracts	13				13
Fair Value, Measurements, Recurring | Level 2 | Natural Gas
Assets at Fair Value
Derivative contracts	4				5
Liabilities at Fair Value
Derivative contracts	258				234
Fair Value, Measurements, Recurring | Level 2 | Fuel Oil
Assets at Fair Value
Derivative contracts	0				0
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 | Interest rate contracts
Liabilities at Fair Value
Derivative contracts	78				90
Fair Value, Measurements, Recurring | Level 2 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[9]			0	[9]
Fair Value, Measurements, Recurring | Level 2 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	696				756
Fair Value, Measurements, Recurring | Level 2 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	161				147
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	369	[10]			317	[10]
Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	34	[11]			15	[11]
Fair Value, Measurements, Recurring | Level 3
Assets at Fair Value
Money market funds	0	[7]			0	[7]
Derivative contracts	156				228
Long-term disability plan	0				0
Nuclear decommissioning trusts	0				0
Total assets	156	[8]			228	[8]
Liabilities at Fair Value
Derivative contracts	818				551
Total liabilities	818				551
Net assets (liabilities)	(662)				(323)
Fair Value, Measurements, Recurring | Level 3 | Electricity
Assets at Fair Value
Derivative contracts	143				218
Liabilities at Fair Value
Derivative contracts	99				77
Fair Value, Measurements, Recurring | Level 3 | Natural Gas
Assets at Fair Value
Derivative contracts	0				0
Liabilities at Fair Value
Derivative contracts	48				23
Fair Value, Measurements, Recurring | Level 3 | Fuel Oil
Assets at Fair Value
Derivative contracts	0				0
Fair Value, Measurements, Recurring | Level 3 | Tolling
Assets at Fair Value
Derivative contracts	13				10
Liabilities at Fair Value
Derivative contracts	671				451
Fair Value, Measurements, Recurring | Level 3 | Interest rate contracts
Liabilities at Fair Value
Derivative contracts	0				0
Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[9]			0	[9]
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	[10]			0	[10]
Fair Value, Measurements, Recurring | Level 3 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[11]			0	[11]
Fair Value, Measurements, Recurring | Netting and Collateral
Assets at Fair Value
Money market funds	0	[12],[7]			0	[12],[7]
Derivative contracts	(110)	[12]			(73)	[12]
Long-term disability plan	0	[12]			0	[12]
Nuclear decommissioning trusts	0	[12]			0	[12]
Total assets	(110)	[12],[8]			(73)	[12],[8]
Liabilities at Fair Value
Derivative contracts	(109)	[12]			(73)	[12]
Total liabilities	(109)	[12]			(73)	[12]
Net assets (liabilities)	(1)	[12]			0	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Electricity
Assets at Fair Value
Derivative contracts	(93)	[12]			(62)	[12]
Liabilities at Fair Value
Derivative contracts	(28)	[12]			(21)	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Natural Gas
Assets at Fair Value
Derivative contracts	(10)	[12]			(7)	[12]
Liabilities at Fair Value
Derivative contracts	(81)	[12]			(52)	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Fuel Oil
Assets at Fair Value
Derivative contracts	(7)	[12]			(4)	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Tolling
Assets at Fair Value
Derivative contracts	0	[12]			0	[12]
Liabilities at Fair Value
Derivative contracts	0	[12]			0	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Interest rate contracts
Liabilities at Fair Value
Derivative contracts	0	[12]			0	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	0	[12],[9]			0	[12],[9]
Fair Value, Measurements, Recurring | Netting and Collateral | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[12]			0	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	0	[12]			0	[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	0	[10],[12]			0	[10],[12]
Fair Value, Measurements, Recurring | Netting and Collateral | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0	[11],[12]			0	[11],[12]
Fair Value, Measurements, Recurring | Total
Assets at Fair Value
Money market funds	1,222	[7]			1,321	[7]
Derivative contracts	207				234
Long-term disability plan	8				8
Nuclear decommissioning trusts	3,867				3,567
Total assets	5,304	[8]			5,130	[8]
Liabilities at Fair Value
Derivative contracts	980				725
Total liabilities	1,058				815
Net assets (liabilities)	4,246				4,315
Fair Value, Measurements, Recurring | Total | Electricity
Assets at Fair Value
Derivative contracts	194				222
Liabilities at Fair Value
Derivative contracts	84				69
Fair Value, Measurements, Recurring | Total | Natural Gas
Assets at Fair Value
Derivative contracts	0				2
Liabilities at Fair Value
Derivative contracts	225				205
Fair Value, Measurements, Recurring | Total | Fuel Oil
Assets at Fair Value
Derivative contracts	0				0
Fair Value, Measurements, Recurring | Total | Tolling
Assets at Fair Value
Derivative contracts	13				10
Liabilities at Fair Value
Derivative contracts	671				451
Fair Value, Measurements, Recurring | Total | Interest rate contracts
Liabilities at Fair Value
Derivative contracts	78				90
Fair Value, Measurements, Recurring | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	2,124	[9]			1,899	[9]
Fair Value, Measurements, Recurring | Total | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	696				756
Fair Value, Measurements, Recurring | Total | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	642				580
Fair Value, Measurements, Recurring | Total | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	369	[10]			317	[10]
Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	$ 36	[11]			$ 15	[11]

[1] Reported in "Competitive power generation" revenue on Edison International's consolidated statements of income.

[2] Due to regulatory mechanisms, SCE's realized and unrealized gains and losses are recorded as regulatory assets and liabilities.

[3] Includes the elimination of the fair value of derivatives with SCE's consolidated affiliates.

[4] Included in reclassification adjustments in Edison International's consolidated statements of other comprehensive income.

[5] Transfers out of Level 3 into Level 2 occurred due to significant observable inputs becoming available as the transactions near maturity.

[6] Amounts reported in "Competitive power generation" revenue on Edison International's consolidated statements of income were $(7) million and $(6) million for the years ended March 31, 2012 and 2011, respectively. The remainder of the unrealized losses relate to SCE. See 2 above.

[7] Money market funds are included in cash and cash equivalents and restricted cash and cash equivalents on Edison International's consolidated balance sheets.

[8] Excludes $30 million and $31 million at March 31, 2012 and December 31, 2011, respectively, of cash surrender value of life insurance investments for deferred compensation.

[9] Approximately 69% and 70% of the equity investments were located in the United States at March 31, 2012 and December 31, 2011, respectively.

[10] At March 31, 2012 and December 31, 2011, corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $38 million and $22 million, respectively.

[11] Excludes net payables of $14 million and net receivables of $25 million at March 31, 2012 and December 31, 2011, respectively, of interest and dividend receivables as well as receivables and payables related to pending securities sales and purchases.

[12] 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.