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Other - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Aug. 04, 2017
May 15, 2017
Feb. 15, 2017
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Other [Line Items]              
Cash dividend paid           $ 1,235,000 $ 1,198,000
Quarterly dividend declared       $ 0.0425 $ 0.0425 $ 0.0850 $ 0.0850
Dividend Paid              
Other [Line Items]              
Cash dividend paid   $ 613,000 $ 613,000        
Dividend declared, date of record   May 01, 2017 Feb. 01, 2017        
Dividend payable       $ 639,000   $ 639,000  
Dividend payable date       Aug. 15, 2017      
Dividend Declared | Subsequent Event              
Other [Line Items]              
Dividend declared, date of record Nov. 01, 2017            
Dividend payable date Nov. 15, 2017            
Dividend declaration date Aug. 04, 2017            
Quarterly dividend declared $ 0.0425