Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Comprehensive Income [Abstract]
Net Income	$ 257	$ 32	$ 235
Gain (losses) from continuing operations on commodity derivatives designated as cash flow hedges:
Losses arising during period		(100)	(129)
Amount of losses reclassified into income	81	135	166
Net gains on commodity derivatives	81	35	37
Losses on treasury rate locks reclassified into income	1	18	5
Amortization of losses for prior service cost	(7)		(13)
Prior service costs arising during period	(4)
Other comprehensive income from continuing operations, before income taxes	71	53	29
Income tax expense related to other comprehensive income from continuing operations	28	21	12
Other comprehensive income from continuing operations, net of income taxes	43	32	17
Other Comprehensive Income from Discontinued Operations, Net of Income Taxes		103	4
Comprehensive Income	$ 300	$ 167	$ 256