Derivative Instruments and Hedging Activities - Fair Values of Derivative Instruments Recorded in Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 3	$ 33
Total Liabilities	216	116
Derivative Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current Assets: Derivative instruments	3	31
Current Liabilities: Derivative instruments	205	116
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
Other Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent Liabilities: Other	$ 11