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Stock Incentive Plans - Summary of Stock Options Exercised and Outstanding (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]        
Intrinsic value of options exercised in the period $ 1,105 $ 1,025    
Stock options:        
Number of options, outstanding stock options 360,100 367,533 400,399 538,697
Number of options, exercisable stock options 208,227      
Weighted average exercise price, outstanding stock option $ 17.35      
Weighted average exercise price, exercisable stock options $ 14.71      
Weighted average contractual term of outstanding stock options 5 years 5 months 1 day      
Weighted average contractual term of exercisable stock options 4 years 7 months 10 days      
Aggregate intrinsic value, outstanding stock option $ 9,430      
Aggregate intrinsic value, exercisable stock option $ 6,003