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Earnings per Share (Narrative) (Details) - USD ($)
3 Months Ended 12 Months Ended
Apr. 26, 2016
Jun. 30, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Earnings per Share [Line Items]          
Total anti-dilutive shares excluded from the calculation (in shares)     250 503 0
Stock repurchase program, period 24 months        
Stock repurchase program, remaining authorized amount     $ 54,000,000    
Maximum [Member]          
Earnings per Share [Line Items]          
Stock repurchase program, authorized amount $ 60,000,000        
Common Stock [Member]          
Earnings per Share [Line Items]          
Common stock repurchased and retired, shares   169,625      
Common stock repurchased and retired, average price per share   $ 35.08      
Common stock repurchased, shares     0 169,625