Consolidated Statement Of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Net income	$ 112		$ 80		$ 242		$ 238
Gain (losses) on commodity derivatives designated as cash flow hedges:
Gains arising during period							2
Amount of losses reclassified into income	6		16		31		62
Net gains on commodity derivatives	6		16		31		64
Losses on treasury rate locks reclassified into income	1		1		1		1
Pension and other postretirement benefit plans	1		(2)		(4)		(6)
Other comprehensive income, before income taxes	8		15		28		59
Income tax expense related to other comprehensive income	4	[1]	6	[1]	12	[2]	24	[2]
Other comprehensive income, net of income taxes	4		9		16		35
Comprehensive Income	$ 116		$ 89		$ 258		$ 273

[1] Includes tax expense for losses reclassified to income during the three months ended September 30, 2012 and 2011 of $2 million and $7 million, respectively.

[2] Includes tax expense for losses reclassified to income during the nine months ended September 30, 2012 and 2011 of $13 million and $25 million, respectively.