Fair Value Measurements - Additional Information (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate notional amount of outstanding foreign currency hedges	$ 1,200,000,000	$ 1,700,000,000
Aggregate notional amount of outstanding interest rate swaps	494,000,000	450,000,000
Estimated fair values of debt instruments	8,300,000,000	7,800,000,000
Carrying values of debt instruments	$ 6,500,000,000	$ 6,500,000,000