Fair values of Derivative Instruments Recorded in Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative asset designated as hedging instruments	$ 1	$ 78
Derivative liabilities designated as hedging instruments	62	76
Current Other Assets [Member] | Electricity commodity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative asset designated as hedging instruments	1	5
Long-term other assets [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative asset designated as hedging instruments		73
Current accrued liabilities [Member] | Electricity commodity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities designated as hedging instruments	4
Current accrued liabilities [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities designated as hedging instruments		42
Long-term accrued liabilities [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities designated as hedging instruments	42	32
Long-term accrued liabilities [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities designated as hedging instruments	$ 16	$ 2