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Stock-Based Compensation - Stock Option Activity (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Stock-Based Compensation      
Stock-based compensation expense $ 10.6 $ 6.9 $ 5.9
Income tax benefit $ 2.2 $ 1.5 1.3
Minimum      
Stock-Based Compensation      
Sum of age and years of service for accelerated vesting on retirement of certain stock options and restricted stock awards 75 years    
Stock Options      
Stock-Based Compensation      
Vesting period 3 years    
Shares      
Outstanding at beginning of year (in shares) 268,000    
Exercised (in shares) (198,000)    
Outstanding at end of year (in shares) 70,000 268,000  
Options exercisable at end of year (in shares) 70,000    
Weighted-Average Exercise Price      
Outstanding at beginning of year (in dollars per share) $ 30.53    
Exercised (in dollars per share) 28.95    
Outstanding at end of year (in dollars per share) $ 34.97 $ 30.53  
Other information      
Intrinsic value of options exercised $ 10.8 $ 3.2 $ 3.5
Weighted-average remaining contractual term of options exercisable 5 years    
Aggregate intrinsic value of options exercisable $ 4.5    
Number of options that are vested and expected to vest (in shares) 100,000    
Weighted average exercise price of options that are vested and expected to vest (in dollars per share) $ 34.97    
Unrecognized compensation cost $ 0.0    
Nonvested at end of year (in shares) 0