Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax benefit from discontinued operations	$ 12
Operating revenues from discontinued operations		441
Loss from discontinued operation before income taxes		175
Pensions and benefits	2,610		2,614
Edison Mission Energy
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of days after bankruptcy filing for settlement transaction (days)	150 days
Number of days for completion of settlement transaction agreement from petition date (days)	210 days
Joint tax liability	185
Receivables from EME	231
Edison Mission Energy | Pension Plans
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pensions and benefits	80
Deconsolidated charges recorded in other comprehensive income	34
Plan Support Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net receivable under plan support agreement	46
Retirement liabilities assumed under plan support agreement	104
Estimated loss under plan support agreement	$ 150