Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009	Dec. 31, 2008
Assets at Fair Value
Money market funds	$ 1,300		$ 1,100
Nuclear decommissioning trusts	3,592		3,480		3,140	2,524
Liabilities at Fair Value
Percentage of equity investments located in the United States (as a percent)	70.00%		67.00%
Collateralized mortgage obligations and other asset backed securities	22		27
Receivables (payables) net related to investments	25		(5)
Cash surrender value of life insurance	31
Total realized/unrealized gains (losses):
Unrealized gain loss related to Level 3 financial instruments reported within competitive power generation revenue	16		13
Stocks
Assets at Fair Value
Nuclear decommissioning trusts	1,899		2,029
Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	756		790
U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	580		288
Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	317		346
Level 3
Fair Value Disclosures Level 3
Fair value, net asset (liabilities) at beginning of period	97		62
Total realized/unrealized gains (losses):
Included in earnings	(19)	[1]	64	[1]
Included in regulatory assets and liabilities	(458)	[2],[3]	58	[2]
Included in accumulated other comprehensive income	1		2
Purchases	81		66
Settlements	(23)		(166)
Transfers in or out of Level 3	(2)		11
Fair value, net asset (liabilities) at end of period	(323)		97
Change during the period in unrealized gains (losses) related to assets and liabilities held at the end of the period	(644)	[4]	143	[4]
Fair Value, Measurements, Recurring [Member] | Level 1
Assets at Fair Value
Money market funds	1,321		1,100	[5]
Long-term disability plan	8		9
Nuclear decommissioning trusts	2,332		2,245
Total assets	3,669		3,363	[6]
Liabilities at Fair Value
Total liabilities	0
Net assets (liabilities)	3,669		3,363
Fair Value, Measurements, Recurring [Member] | Level 1 | Commodity Contracts
Assets at Fair Value
Derivative contracts	8		9
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Natural Gas
Assets at Fair Value
Derivative contracts	4		1
Fair Value, Measurements, Recurring [Member] | Level 1 | Fuel Oil
Assets at Fair Value
Derivative contracts	4		8
Fair Value, Measurements, Recurring [Member] | Level 1 | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	1,899		2,029	[7]
Fair Value, Measurements, Recurring [Member] | Level 1 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	433		215
Fair Value, Measurements, Recurring [Member] | Level 1 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	0		1	[8]
Fair Value, Measurements, Recurring [Member] | Level 2
Assets at Fair Value
Nuclear decommissioning trusts	1,235		1,240
Total assets	1,306		1,379	[6]
Liabilities at Fair Value
Total liabilities	337		316
Net assets (liabilities)	969		1,063
Fair Value, Measurements, Recurring [Member] | Level 2 | Commodity Contracts
Assets at Fair Value
Derivative contracts	71		139
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	247		300
Fair Value, Measurements, Recurring [Member] | Level 2 | Electricity
Assets at Fair Value
Derivative contracts	66		70
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	13		13
Fair Value, Measurements, Recurring [Member] | Level 2 | Natural Gas
Assets at Fair Value
Derivative contracts	5		69
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	234		286
Fair Value, Measurements, Recurring [Member] | Level 2 | Coal
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure			1
Fair Value, Measurements, Recurring [Member] | Level 2 | Interest rate contracts
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	90		16
Fair Value, Measurements, Recurring [Member] | Level 2 | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	756		790
Fair Value, Measurements, Recurring [Member] | Level 2 | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	147		73
Fair Value, Measurements, Recurring [Member] | Level 2 | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	317		346	[9]
Fair Value, Measurements, Recurring [Member] | Level 2 | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	15		31	[8]
Fair Value, Measurements, Recurring [Member] | Level 3
Assets at Fair Value
Total assets	228		492	[6]
Liabilities at Fair Value
Total liabilities	551		395
Net assets (liabilities)	(323)		97
Fair Value, Measurements, Recurring [Member] | Level 3 | Commodity Contracts
Assets at Fair Value
Derivative contracts	228		492
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	551		395
Fair Value, Measurements, Recurring [Member] | Level 3 | Electricity
Assets at Fair Value
Derivative contracts	218		363
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	77		40
Fair Value, Measurements, Recurring [Member] | Level 3 | Natural Gas
Assets at Fair Value
Derivative contracts	0		11
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	23		11
Fair Value, Measurements, Recurring [Member] | Level 3 | Tolling
Assets at Fair Value
Derivative contracts	10		118
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	451		344
Fair Value, Measurements, Recurring [Member] | Netting and Collateral
Assets at Fair Value
Total assets	(73)		(70)	[10],[6]
Liabilities at Fair Value
Total liabilities	(73)		(26)	[10]
Net assets (liabilities)	0		(44)	[10]
Fair Value, Measurements, Recurring [Member] | Netting and Collateral | Commodity Contracts
Assets at Fair Value
Derivative contracts	(73)		(70)	[10]
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(73)		(26)	[10]
Fair Value, Measurements, Recurring [Member] | Netting and Collateral | Electricity
Assets at Fair Value
Derivative contracts	(62)		(61)	[10]
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(21)		(21)	[10]
Fair Value, Measurements, Recurring [Member] | Netting and Collateral | Natural Gas
Assets at Fair Value
Derivative contracts	(7)		(1)	[10]
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(52)		(4)	[10]
Fair Value, Measurements, Recurring [Member] | Netting and Collateral | Fuel Oil
Assets at Fair Value
Derivative contracts	(4)		(8)	[10]
Fair Value, Measurements, Recurring [Member] | Netting and Collateral | Coal
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure			(1)	[10]
Fair Value, Measurements, Recurring [Member] | Total
Assets at Fair Value
Money market funds	1,321		1,100	[5]
Long-term disability plan	8		9
Nuclear decommissioning trusts	3,567		3,485
Total assets	5,130		5,164	[6]
Liabilities at Fair Value
Total liabilities	815		685
Net assets (liabilities)	4,315		4,479
Fair Value, Measurements, Recurring [Member] | Total | Commodity Contracts
Assets at Fair Value
Derivative contracts	234		570
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	725		669
Fair Value, Measurements, Recurring [Member] | Total | Electricity
Assets at Fair Value
Derivative contracts	222		372
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	69		32
Fair Value, Measurements, Recurring [Member] | Total | Natural Gas
Assets at Fair Value
Derivative contracts	2		80
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	205		293
Fair Value, Measurements, Recurring [Member] | Total | Tolling
Assets at Fair Value
Derivative contracts	10		118
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	451		344
Fair Value, Measurements, Recurring [Member] | Total | Interest rate contracts
Liabilities at Fair Value
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	90		16
Fair Value, Measurements, Recurring [Member] | Total | Stocks
Assets at Fair Value
Nuclear decommissioning trusts	1,899		2,029	[7]
Fair Value, Measurements, Recurring [Member] | Total | Municipal bonds
Assets at Fair Value
Nuclear decommissioning trusts	756		790
Fair Value, Measurements, Recurring [Member] | Total | U.S. government and agency securities
Assets at Fair Value
Nuclear decommissioning trusts	580		288
Fair Value, Measurements, Recurring [Member] | Total | Corporate bonds
Assets at Fair Value
Nuclear decommissioning trusts	317		346	[9]
Fair Value, Measurements, Recurring [Member] | Total | Short-term investments, primarily cash equivalents
Assets at Fair Value
Nuclear decommissioning trusts	$ 15		$ 32	[8]

[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] Amounts reported in "Competitive power generation" revenue on Edison International's consolidated statements of income were $16 million and $13 million for the years ended December 31, 2011 and 2010, respectively. The remainder of the unrealized losses relate to SCE. See 2 above.

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

[6] Excludes $31 million at both December 31, 2011 and 2010, of cash surrender value of life insurance investments for deferred compensation.

[7] Approximately 70% and 67% of the equity investments were located in the United States at December 31, 2011 and 2010, respectively.

[8] Excludes net receivables of $25 million and net liabilities of $5 million at December 31, 2011 and 2010, respectively, of interest and dividend receivables and receivables related to pending securities sales and payables related to pending securities purchases.

[9] At December 31, 2011 and 2010, corporate bonds were diversified and included collateralized mortgage obligations and other asset backed securities of $22 million and $27 million, respectively.

[10] 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.