v2.4.0.6
Weighted-Average Assumptions used to Estimate the Fair Values of the Stock Options Granted (Detail) (USD $)
12 Months Ended
Dec. 31, 2011
Year
Dec. 31, 2010
Year
Dec. 31, 2009
Year
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]      
Risk-free interest rate 2.30% 1.90% 2.60%
Expected volatility 33.00% 35.00% 37.00%
Expected life (in years) 5.9 5.4 5.8
Dividend yield 0.00% 0.00% 0.00%
Weighted-average estimated fair value of options granted during the year $ 210.07 $ 216.43 $ 160.63