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Compensation Plans (Details)
$ in Millions
3 Months Ended
Mar. 31, 2019
USD ($)
Dec. 31, 2018
Mar. 31, 2019
USD ($)
shares
Mar. 31, 2018
USD ($)
Performance Shares (PSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, award vesting period   3 years    
Stock-based compensation expense     $ 2.8 $ 2.4
Unrecognized stock based compensation expense $ 15.9   15.9  
Restricted Stock Units (RSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, award vesting period 3 years      
Stock-based compensation expense     2.7 $ 2.7
Unrecognized stock based compensation expense $ 16.4   $ 16.4  
Number of shares represented by each RSU | shares     1  
Minimum [Member] | Performance Shares (PSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Multiplier applied to PSU awards at settlement   0    
Maximum [Member] | Performance Shares (PSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Multiplier applied to PSU awards at settlement   2