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Other - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Nov. 03, 2015
Aug. 14, 2015
May. 15, 2015
Feb. 13, 2015
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Other [Line Items]                
Cash dividend paid   $ 523,000 $ 520,000 $ 514,000     $ 1,557,000 $ 1,517,000
Dividend payable         $ 596,000   $ 596,000  
Dividend payable date         Nov. 13, 2015      
Quarterly dividend declared         $ 0.0425 $ 0.0375 $ 0.1175 $ 0.1125
Subsequent Event | Dividend Declared                
Other [Line Items]                
Dividend payable date Feb. 15, 2016              
Dividend declaration date Nov. 03, 2015              
Quarterly dividend declared $ 0.0425              
Dividend declared, date of record Feb. 01, 2016