Accumulated Other Comprehensive Loss (Schedule Of Income Tax Expense (Benefit) Allocated To Accumulated Other Comprehensive Income Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ 10	$ 28	$ 21
Commodity Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	16	32	14
Treasury Lock [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income			7
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ (6)	$ (4)