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Capital Stock - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Capital Unit [Line Items]        
Preferred stock, par value (dollars per share) $ 50 $ 50    
Cumulative preferred nonvoting stock (as a percent) 4.50% 4.50%    
Preferred stock included in Treasury shares at cost line of the Consolidated Balance Sheet $ 289,254,000 $ 295,070,000    
Common stock, shares authorized 180,000,000 180,000,000    
Common stock, par value (dollars per share) $ 0 $ 0    
Common stock, shares outstanding 37,736,578 37,372,474    
4 1/2% Cumulative Preferred Nonvoting Stock        
Capital Unit [Line Items]        
Preferred stock, shares authorized 100,000      
Preferred stock, par value (dollars per share) $ 50      
Cumulative preferred nonvoting stock (as a percent) 4.50%      
Preferred stock, callable price per share (dollars per share) $ 52.50      
Preferred stock, shares issued 71,340      
Shares held in treasury (in shares) 52,878      
Preferred stock repurchased and subsequently canceled (in shares) 33      
Preferred stock included in Treasury shares at cost line of the Consolidated Balance Sheet $ 1,800,000      
Treasury purchases (in shares)   0 0  
Second Cumulative Preferred Voting Stock        
Capital Unit [Line Items]        
Preferred stock, shares authorized 1,000,000      
Preferred stock, par value (dollars per share) $ 10      
Preferred stock, shares issued 0 0    
Common Stock        
Capital Unit [Line Items]        
Treasury purchases (in shares) 0 0 0  
Common stock, shares outstanding 62,081,391 62,081,391 62,081,391 62,081,391
Treasury Stock        
Capital Unit [Line Items]        
Treasury purchases (in shares) 40,429 59,056 107,096  
Common stock, shares outstanding 24,344,813 24,708,917 24,633,081 24,575,624
Share Repurchase Program, May 2015 | Common Stock        
Capital Unit [Line Items]        
Treasury purchases (in shares) 0 0    
Stock repurchased program, authorized amount (up to) $ 100,000,000      
Share Repurchase Program, May 2015 | Treasury Stock        
Capital Unit [Line Items]        
Treasury purchases (in shares)   150,000