Derivative Instruments and Hedging Activities - Fair Values of Derivative Instruments Recorded in Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 33	$ 332
Total Liabilities	116	154
Derivative Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current Assets: Derivative instruments	31	304
Current Liabilities: Derivative instruments	116	113
Deferred Charges And Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets: Deferred charges and other	2	28
Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent Liabilities: Other		$ 41