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Shareholders' Equity - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Jun. 10, 2017
Jan. 31, 2017
Dec. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
May 16, 2017
Aug. 13, 2012
Dec. 28, 2006
Class of Stock [Line Items]                  
Issuance of common stock Dividend Reinvestment Plan       100,000,000 100,000,000        
Number of stock option granted         128,000 105,000      
Share-based compensation expense       $ 3,100,000 $ 1,700,000 $ 2,200,000      
Tax benefit related to stock based compensation expense       $ 500,000 0 200,000      
Discount from market price       15.00%          
Employees offering dates intervals       6 months          
Number of shares authorized in employee stock purchase plan       1,500,000          
Employee stock purchase plan period       10 years          
Employee stock purchase plan number of shares remain available for future issuance       1,300,000          
Employee stock purchase plan expense       $ 90,000 $ 83,000 $ 71,000      
Estimated weighted-average fair value of stock options granted         $ 2.68 $ 2.07      
Expected volatility rate         39.00% 39.00%      
Expected term period         6 years 3 months 18 days 6 years 6 months      
Risk-free interest rate         2.20% 2.10%      
Expected dividend rate         3.30% 3.60%      
Cash received from employee stock option exercised       100,000 $ 1,100,000 $ 1,300,000      
Intrinsic value of option exercised       $ 24,000,000 $ 2,600,000 $ 1,000,000      
Warrants issued to acquire Icarus Share                 250,000
Warrants exercise price                 $ 9.07
Warrants expiration date       Dec. 26, 2016          
Common stock, shares issued       34,953,825 34,707,924        
Warrant outstanding     0     0      
Aggregate value transaction value of share purchased           $ 1,238,000      
Common Stock [Member]                  
Class of Stock [Line Items]                  
Common stock, shares issued     89,640     89,640      
Shares issued, price per share     $ 9.07     $ 9.07      
Share purchased           105,000      
Aggregate value transaction value of share purchased           $ 1,000      
Common Stock [Member] | Former Owner of Subsidiary Acquired [Member]                  
Class of Stock [Line Items]                  
Share purchased           30,000      
Aggregate value transaction value of share purchased           $ 200,000      
Common Stock [Member] | Current Segment President [Member]                  
Class of Stock [Line Items]                  
Share purchased     75,000     75,000      
Aggregate value transaction value of share purchased   $ 1,100,000              
Performance Units [Member]                  
Class of Stock [Line Items]                  
Maximum shares of common stock participant could receive upon vesting 77,778                
Common stock price threshold consecutive trading days 30 days                
Period to earn units based on stock price during thirty consecutive trading days 2 years                
Performance Units [Member] | Chief Executive Officer [Member]                  
Class of Stock [Line Items]                  
2017 stock options or stock awards, vesting period 3 years                
Number of stock awards granted 700,000                
Fair value of stock awards granted $ 175,000                
Restricted Stock and Performance Units [Member]                  
Class of Stock [Line Items]                  
Unrecognized compensation expense related to stock options and restricted stock       $ 6,300,000          
Weighted average vesting period       2 years 3 months 18 days          
Dividend Reinvestment Plan [Member]                  
Class of Stock [Line Items]                  
Issuance of common stock Dividend Reinvestment Plan               750,000  
2017 Plan [Member]                  
Class of Stock [Line Items]                  
Shares available for future grant       1,300,000          
2017 Plan [Member] | Common Stock [Member]                  
Class of Stock [Line Items]                  
Number of shares reserved for issuance             1,900,000    
2017 Plan [Member] | Minimum [Member]                  
Class of Stock [Line Items]                  
2017 stock options or stock awards, vesting period       3 years          
2017 Plan [Member] | Maximum [Member]                  
Class of Stock [Line Items]                  
2017 stock options or stock awards, vesting period       4 years          
2017 Plan [Member] | Employee Stock Option [Member]                  
Class of Stock [Line Items]                  
2017 stock options or stock awards, vesting period       4 years          
2007 Plan [Member]                  
Class of Stock [Line Items]                  
Number of stock option granted       0