Derivatives and Other Financial Instruments (Schedule Of Carrying Values And Fair Values Of Other Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Short-Term Borrowings [Member]
Derivative [Line Items]
Carrying value	$ 62	$ 92
Fair value	62	92
Commercial Paper [Member]
Derivative [Line Items]
Carrying value	224
Fair value	224
Long-Term Debt Due Within One Year [Member]
Derivative [Line Items]
Carrying value	445	231
Fair value	445	231
Long-Term Debt, Less Amount Due Within One Year [Member]
Derivative [Line Items]
Carrying value	8,640	8,842
Fair value	9,274	9,882
Cash And Cash Equivalents [Member]
Derivative [Line Items]
Carrying value	1,939	1,543
Fair value	1,939	1,543
Restricted Cash [Member]
Derivative [Line Items]
Carrying value	25	1
Fair value	25	1
Noncurrent Receivables [Member]
Derivative [Line Items]
Carrying value	30	23
Fair value	30	23
Available-For-Sale Securities [Member]
Derivative [Line Items]
Carrying value	92	93
Fair value	$ 92	$ 93