Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements Of Comprehensive Income [Abstract]
Net Income	$ 68	$ 64
Gains (losses) on commodity derivatives designated as cash flow hedges:
Losses arising during period		(1)
Amount of losses reclassified into income	13	27
Net gains on commodity derivatives	13	26
Amortization of gains for prior service costs	1	1
Other comprehensive income, before income taxes	14	27
Income tax expense related to other comprehensive income	6	11
Other comprehensive income, net of income taxes	8	16
Comprehensive Income	$ 76	$ 80