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Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Dec. 31, 2015
Dec. 31, 2014
Income Taxes [Line Items]            
Income before income taxes $ 3,679,000 $ 2,254,000 $ 12,229,000 $ 10,896,000    
Income tax provision $ 1,141,000 $ 788,000 $ 3,149,000 $ 2,327,000    
Effective tax rate 31.00%   25.80% 21.40%   22.10%
Increase in uncertain tax positions $ 201,000   $ 201,000      
Generated between 2010 and 2011 | Research and Development Credit            
Income Taxes [Line Items]            
Provision for open audit matters,impact of interest, penalties and other factors     $ 141,000      
Scenario, Forecast            
Income Taxes [Line Items]            
Effective tax rate 24.30%   24.30%   22.01%  
Maximum            
Income Taxes [Line Items]            
Net operating loss and business tax credit carry forwards expiration date     At various dates through December 2032.      
Available to Reduce Future Federal Income Taxes            
Income Taxes [Line Items]            
Net operating loss carry forwards $ 43,387,000   $ 43,387,000      
Business tax credit carry forwards $ 1,782,000   $ 1,782,000