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Stock-based Compensation Plans (Details)
shares in Thousands, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
USD ($)
Mar. 31, 2021
USD ($)
Jun. 30, 2020
USD ($)
Mar. 31, 2020
USD ($)
Jun. 30, 2021
USD ($)
performanceCondition
shares
Jun. 30, 2020
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation | $ $ 7.1 $ 5.5 $ 6.1 $ 4.3    
Stock-based compensation expense | $ 7.1   6.1   $ 12.6 $ 10.4
Common Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation | $ $ 7.1 $ 5.5 $ 6.1 $ 4.3    
Performance Shares            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Service period vested         3 years  
Number of performance conditions | performanceCondition         2  
Number of Units Awarded (in shares) | shares         27  
Share-based Compensation Award, Tranche One | Restricted Stock Units (RSUs)            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of Units Awarded (in shares) | shares         63  
Award vesting period         3 years  
Share-based Compensation Award, Tranche Two | Restricted Stock Units (RSUs)            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Service period vested         1 year  
Number of Units Awarded (in shares) | shares         5