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Earnings Per Share (Details) - $ / shares
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Earnings Per Share [Abstract]    
Weighted average number of common shares outstanding, basic (in shares) 53,515,000 53,315,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted average number of common shares outstanding, diluted (in shares) 53,682,000 53,535,000
Effect of dilutive shares on earnings per share (usd per share) $ 0.00 $ (0.01)
Antidilutive shares excluded from computation of earnings per share (in shares) 0 0
Restricted Share Units    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dilutive securities (in shares) 82,000 78,000
Performance Share Units    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dilutive securities (in shares) 66,000 121,000
Purchase Match Units    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dilutive securities (in shares) 19,000 21,000