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Estimated Fair Value of Options Granted using Black-Scholes Option-Pricing Model with Weighted-Average Assumptions (Detail)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Expected life (years) 6 years 2 months 12 days 6 years 2 months 12 days 5 years 10 months 24 days
Risk-free interest rate 1.60% 0.80% 1.40%
Expected volatility 46.00% 51.40% 50.60%
Expected dividend yield