Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total operating expenses					$ 8,458	$ 7,512	$ 7,437
Disposal Group, Income tax expense (benefit)					0	29	1
Discontinued Operations Income (Loss), net of tax	(56)	1	(1)	0	0	(56)	(3)
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Operating Revenues						55	39
Disposal Group, Operation and maintenance						24	16
Disposal Group, Depreciation, Depletion and Amortization						23	18
Disposal Group, Taxes Other than Income						4	3
Disposal Group, Assets (Gains) and Losses, Net						83	0
Total operating expenses						134	37
Disposal Group, Operating Income (Loss)						(79)	2
Disposal Group, Other (income) and deductions						6	6
Disposal Group, Income (Loss) from Discontinued Operation, before Income Tax						(85)	(4)
Disposal Group, Income tax expense (benefit)						(29)	(1)
Discontinued Operations Income (Loss), net of tax						$ (56)	$ (3)