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Equity Transactions - Additional Information (Detail) - USD ($)
shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Stockholders Equity [Line Items]      
Preferred stock authorized but unissued and undesignated 10,000 10,000  
Expiration date on repurchase authorizations Dec. 31, 2019    
Aggregate cost shares of common stock $ 9,606 $ 1,510 $ 15,367
Common stock acquired, shares 91    
Maximum      
Stockholders Equity [Line Items]      
Authorization amount for repurchase of common stock $ 175,000    
Common Stock [Member]      
Stockholders Equity [Line Items]      
Cumulative common stock acquired, shares 3,600    
Since Initial Approval of Share Repurchase Plan in 2011 [Member]      
Stockholders Equity [Line Items]      
Aggregate cost shares of common stock $ 86,898    
Remaining authorized repurchase amount $ 88,102