Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Edison Mission Energy	Sep. 30, 2013 Edison Mission Energy	Sep. 30, 2013 Edison Mission Energy Pension Plans	Sep. 30, 2013 Plan Support Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense from discontinued operations		$ 25			$ 25	$ 1
Operating revenues from discontinued operations	461		1,310
Loss from discontinued operation before income taxes	262		645
Pensions and benefits		2,237		2,614			80
Joint tax liability					192	192
Receivables from EME					238	238
Deconsolidated charges recorded in accumulated other comprehensive income							34
Net receivable under plan support agreement								46
Retirement liabilities assumed under plan support agreement								104
Estimated loss under plan support agreement								$ 150