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Stockholders' Equity - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Dec. 31, 2014
Stockholders Equity [Line Items]      
Common stock, shares issued 92,889,547 92,637,403  
Treasury stock, shares 6,519,773 6,519,773  
Dividends payable $ 136,000 $ 470,000  
Share Repurchase Program, authorized amount     $ 250,000,000
Share Repurchase Program [Member]      
Stockholders Equity [Line Items]      
Share Repurchase Program, remaining authorized repurchase amount $ 190,000,000    
Stock Repurchase Program, number of shares repurchased 0    
Common Stock [Member]      
Stockholders Equity [Line Items]      
Common stock, shares issued 92,889,547 92,637,403  
Number of unvested shares 2,202,672    
Restricted Stock Units [Member]      
Stockholders Equity [Line Items]      
Number of unvested shares 1,850,070