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Stockholders' Equity - Stock Option Activities of Stock Option Plans (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Stockholders Equity [Line Items]      
Shares outstanding at beginning of year 955,848    
Granted, Shares 135,000    
Exercised, Shares (159,348)    
Cancelled, forfeited or expired, Shares (88,720)    
Shares outstanding at end of year 842,780 955,848  
Shares exercisable at end of year 252,925    
Outstanding at beginning of year, Weighted-Average Exercise Price $ 27.09    
Granted, Weighted-Average Exercise Price 38.73    
Exercised, Weighted-Average Exercise Price 11.20    
Forfeited or expired, Weighted-Average Exercise Price 27.29    
Outstanding at end of year, Weighted-Average Exercise Price 31.93 $ 27.09  
Exercisable at end of year, Weighted-Average Exercise Price 28.13    
Weighted-average fair value per option granted during year $ 14.19 $ 14.85  
Total intrinsic value of options exercised during the year $ 4,292,000 $ 3,461,000 $ 2,970,000
Total fair value of options vested during the year $ 2,411,000 $ 1,502,000 $ 1,565,000
2008 Plan [Member]      
Stockholders Equity [Line Items]      
Maximum number of securities for issuance 1,975,000 1,975,000  
Number of awards available to be granted 797,890    
Shares outstanding at end of year 802,780    
Shares exercisable at end of year 232,925    
Outside Director Plan [Member]      
Stockholders Equity [Line Items]      
Maximum number of securities for issuance 400,000    
Number of awards available to be granted 278,456