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Other - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 08, 2018
Feb. 15, 2018
Mar. 31, 2018
Mar. 31, 2017
Other [Line Items]        
Quarterly dividend declared     $ 0.0425 $ 0.0425
Cash dividend paid     $ 652,000 $ 613,000
Dividend Declared        
Other [Line Items]        
Dividend declaration date Mar. 08, 2018      
Quarterly dividend declared $ 0.0425      
Dividend payable date Mar. 15, 2018      
Dividend declared, date of record May 01, 2018      
Dividend payable     $ 900,000  
Dividend Paid        
Other [Line Items]        
Dividend declared, date of record   Feb. 01, 2018    
Cash dividend paid   $ 624,000