Fair Value Measurements (Schedule Of Commodity Derivatives) (Details) (Commodity [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of commodity derivatives	$ (93)
Unobservable Inputs	Discount for inactive markets and/or illiquid locations (2)	[1]
Market Approach [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Market approach (1)	[2]

[1] Significant increases or decreases in any of these inputs in isolation would have a limited impact on fair value measurement. Generally, a change in the fair value measurement is linearly based on changes in these inputs.

[2] The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities. The commodity derivatives are valued using quoted prices or internally developed models with observable inputs, adjusted for certain contracts that are traded in inactive markets and/or at illiquid locations. The unobservable inputs used in the Companies' models do not have a significant impact on the valuation.