Fair Value Measurements - Additional Information (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
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	$ 1,300,000,000
Aggregate notional amount of outstanding interest rate swaps	968,000,000	503,000,000
Estimated fair values of debt instruments	7,900,000,000	8,200,000,000
Outstanding principal amount of debt instrument	7,200,000,000	7,200,000,000
Unamortized discount on long-term debt	$ 890,000,000	$ 892,000,000