Derivatives and Other Financial Instruments - Schedule of Carrying Values and Fair Values of Other Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Cash and Cash Equivalents [Member]
Derivative [Line Items]
Carrying value	$ 1,432	$ 1,939
Fair value	1,432	1,939
Restricted Cash [Member]
Derivative [Line Items]
Carrying value	224	25
Fair value	224	25
Noncurrent Receivables [Member]
Derivative [Line Items]
Carrying value	21	30
Fair value	21	30
Available-for-sale securities [Member]
Derivative [Line Items]
Carrying value	89	92
Fair value	89	92
Short-term Debt [Member]
Derivative [Line Items]
Carrying value	591	62
Fair value	591	62
Commercial Paper [Member]
Derivative [Line Items]
Carrying value	43	224
Fair value	43	224
Long Term Debt Due Within One Year [Member]
Derivative [Line Items]
Carrying value	540	445
Fair value	540	445
Long-Term Debt, Less Amount Due Within One Year [Member]
Derivative [Line Items]
Carrying value	8,350	8,640
Fair value	$ 9,253	$ 9,274