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Stockholders' Equity - Additional Information (Details) - USD ($)
 12 Months Ended
Feb. 19, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Nov. 30, 2014
Apr. 30, 2014
Class of Stock [Line Items]            
Common stock, shares authorized   90,000,000 90,000,000      
Common stock, par value (usd per share)   $ 1 $ 1      
Common stock, shares issued   66,100,000 65,400,000      
Common stock, shares outstanding   60,000,000 59,600,000      
Preference stock, shares authorized   800,000        
Preference stock, par value (usd per share)   $ 1        
Cash dividends declared per common share (usd per share)   $ 0.28 $ 0.28 $ 0.25    
Share repurchase program, authorized amount           $ 15,000,000
Shares acquired       724,792    
Stock repurchase program, amount acquired     $ 37,800,000 $ 10,600,000    
Cash dividends paid to stockholders   $ 16,800,000 $ 16,900,000 $ 15,600,000    
Subsequent Event            
Class of Stock [Line Items]            
Cash dividends declared per common share (usd per share) $ 0.07          
November 2014 Repurchase Program [Member]            
Class of Stock [Line Items]            
Share repurchase program, authorized amount         $ 75,000,000  
Shares acquired   0 2,961,007      
Stock repurchase program, amount acquired     $ 37,800,000