Fair Value Measurements (Schedule Of Carrying Value And Fair Value Measurement Information For Financial Assets And Liabilities) (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Short-Term Investments [Member] | Carrying Amount [Member]
Investments	$ 3,367	$ 145
Short-Term Investments [Member] | Total Fair Value [Member]
Investments	3,367	145
Short-Term Investments [Member] | Level 1 Inputs [Member]
Investments	3,367	145
Long-Term Investments [Member]
Investments	93	94	97	115
Long-Term Investments [Member] | Carrying Amount [Member]
Investments	93	94
Long-Term Investments [Member] | Total Fair Value [Member]
Investments	93	94
Long-Term Investments [Member] | Level 3 Inputs [Member]
Investments	93	94
Carrying Amount [Member]
Commodity derivatives	321	249
Commodity derivatives	(161)	(192)
Interest rate derivatives	111	140
Debt	(7,930)	(5,630)
Total Fair Value [Member]
Commodity derivatives	321	249
Commodity derivatives	(161)	(192)
Interest rate derivatives	111	140
Debt	(8,867)	(6,629)
Level 1 Inputs [Member]
Debt	(2,340)
Level 2 Inputs [Member]
Commodity derivatives	321	249
Commodity derivatives	(161)	(192)
Interest rate derivatives	111	140
Debt	(6,423)	(6,485)
Level 3 Inputs [Member]
Debt	$ (104)	$ (144)