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Shares Repurchased - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Apr. 27, 2016
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Apr. 11, 2018
Oct. 29, 2014
Maximum [Member]              
Class of Stock [Line Items]              
Total Leverage Ratio           175.00%  
Three-Year Share Repurchase Program [Member]              
Class of Stock [Line Items]              
Common stock purchase authorized amount             $ 100,000,000
Share repurchase program, increase in authorized amount $ 60,000,000            
Share repurchase program, extended term date Apr. 27, 2019            
Repurchased common stock, shares   47,816 47,317 135,041 401,813    
Repurchased common stock, value   $ 424,000 $ 484,000 $ 1,430,000 $ 4,178,000    
Dollar amount remaining available for future share repurchases   $ 87,184,000   $ 87,184,000