Accumulated Other Comprehensive Loss (Schedule Of Income Tax Expense (Benefit) Allocated To Accumulated Other Comprehensive Income Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ 6		$ 11
Tax expense for losses reclassified to income	5		11
Commodity Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	5	[1]	11	[1]
Prior Service Cost [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense related to other comprehensive income	$ 1	[2]

[1] Includes tax expense for losses reclassified to income during the three months ended March 31, 2012 and 2011, of $5 million and $11 million, respectively.

[2] No material income tax effect of losses reclassified to income in the current period.