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Stockholders' Equity - Narrative - Restricted Stock Awards and Stock Option Grants (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Class of Stock [Line Items]      
Number of securities called to be received (in shares) 1    
Award vesting period 4 years    
Deferred and Matching Restricted Stock Units      
Class of Stock [Line Items]      
Stock issued during period, MSPP (in shares) 0    
Restricted Stock Awards      
Class of Stock [Line Items]      
Options vested in period, fair value $ 3.8 $ 3.7 $ 3.3
Grants in period, weighted average grant date fair value (USD per share) $ 16.97 $ 17.43 $ 17.47
Compensation not yet recognized, share-based awards other than options $ 7.1 $ 6.3  
Compensation cost not yet recognized, period for recognition 1 year 8 months 4 days 1 year 8 months 8 days  
Award vesting period 4 years    
Performance Restricted Stock Units      
Class of Stock [Line Items]      
Grants in period, weighted average grant date fair value (USD per share) $ 19.73 $ 17.00 $ 17.34
Compensation not yet recognized, share-based awards other than options $ 1.0 $ 0.9  
Compensation cost not yet recognized, period for recognition 1 year 9 months 1 year 8 months 26 days  
Award vesting period 3 years    
Total unrecognized compensation costs related to stock option awards (in years) $ 0.9 $ 0.8 $ 0.8
Stock Option Awards      
Class of Stock [Line Items]      
Compensation cost not yet recognized, period for recognition 1 year 8 months 4 days 1 year 8 months 8 days  
Weighted average grant price (in dollars per share) $ 6.30 $ 5.98 $ 6.30
Total unrecognized compensation costs related to stock option awards $ 2.8 $ 2.7