XML 15 R39.htm IDEA: XBRL DOCUMENT v2.4.0.6
Weighted Average Assumptions of Options Granted (Detail)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Stock Options
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 29.37% 29.59% 31.99%
Risk-free interest rate 0.75% 2.04% 1.97%
Dividend yield 0.00% 0.00% 0.00%
Expected term (years) 5 years 6 months 29 days 5 years 10 months 2 days 5 years 8 months 16 days
Employee Stock
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 32.04% 23.94% 20.20%
Risk-free interest rate 0.09% 0.14% 0.16%
Dividend yield 0.00% 0.00% 0.00%
Expected term (years) 6 months 6 months 6 months