• Filing Date: 2018-03-07
  • Form Type: 10-K
  • Description: Annual report
v3.8.0.1
Stockholders' Equity (Common Stock) - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Class of Stock [Line Items]      
Stock repurchased and retired, total costs $ 21,318,000 $ 464,000 $ 792,000
Common Stock [Member]      
Class of Stock [Line Items]      
Repurchase and retirement of common stock, shares 437,240 14,934 17,493
2017 Plan [Member]      
Class of Stock [Line Items]      
Common stock repurchase authorized amount $ 20,000,000    
Time through the company is allowed to repurchase shares Dec. 31, 2018    
Share Repurchase Plan [Member]      
Class of Stock [Line Items]      
Stock repurchased and retired, total costs $ 15,154,000 $ 20,026,000 $ 1,610,000
Share Repurchase Plan [Member] | Common Stock [Member]      
Class of Stock [Line Items]      
Repurchase and retirement of common stock, shares 433,175 643,703 37,869
Share Repurchase Plan [Member] | 2016 and 2015 Plan [Member]      
Class of Stock [Line Items]      
Common stock repurchase authorized amount   $ 20,000,000 $ 20,000,000
Common stock repurchased and retired, weighted average price $ 34.94 $ 31.07  
Stock repurchased and retired, total costs $ 15,155,000 $ 20,026,000  
Fees and commissions average price repurchase common stock $ 34.98 $ 31.11  
Share Repurchase Plan [Member] | 2016 and 2015 Plan [Member] | Common Stock [Member]      
Class of Stock [Line Items]      
Repurchase and retirement of common stock, shares 433,175 643,703