Accumulated Other Comprehensive Loss (Schedule Of Income Tax Expense (Benefit) Allocated To Accumulated Other Comprehensive Income Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ 2	[1]	$ 7	[1]	$ 8	[2]	$ 18	[2]
Tax expense for losses reclassified to income	6		9		11		20
Commodity Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	6	[1]	9	[1]	11	[2]	19	[2]
Pension And Other Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ (4)	[1],[3]	$ (2)	[1],[3]	$ (3)	[2],[3]	$ (1)	[2],[3]

[1] Includes tax expense for losses reclassified to income during the three months ended June 30, 2012 and 2011 of $6 million and $9 million, respectively.

[2] Includes tax expense for losses reclassified to income during the six months ended June 30, 2012 and 2011 of $11 million and $20 million, respectively.

[3] No material income tax effect of losses reclassified to income in the current periods.