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Share-based Compensation - Fair Values of Employee Stock Options for Option Grants Issued Valuation Assumptions Using Black-Scholes Option Model (Detail) (USD $)
9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Equity [Abstract]    
Dividend yield 1.80% 1.80%
Volatility 45.20% 57.90%
Risk-free interest rate 2.00% 1.60%
Weighted average expected option term (in years) 5 years 6 months 5 years 7 months 6 days
Weighted average fair value per share of options granted $ 2.81 $ 3.00