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Stock-Based Compensation - Restricted Stock Units (Details)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2021
USD ($)
$ / shares
shares
Dec. 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Stock-based compensation      
Stock-based compensation expense | $ $ 13.1 $ 10.0 $ 7.8
Period for recognition of unrecognized compensation expense 7 months 6 days    
Restricted Stock Units      
Stock-based compensation      
Ratio of common stock for each vested award 1    
Number of Shares      
Unvested as of beginning of period (in shares) | shares 43,550 44,783 48,761
Granted (in shares) | shares 198,771 28,783 20,418
Vested (in shares) | shares (49,519) (30,016) (22,452)
Forfeited (in shares) | shares (7,473)   (1,944)
Unvested as of end of period (in shares) | shares 185,329 43,550 44,783
Weighted Average Grant Date Fair Value      
Unvested as of beginning of period (in dollars per share) | $ / shares $ 21.93 $ 27.82 $ 28.60
Granted (in dollars per share) | $ / shares 27.13 15.86 26.50
Vested (in dollars per share) | $ / shares 23.08 27.47 28.37
Forfeited (in dollars per share) | $ / shares 26.37   28.29
Unvested as of end of period (in dollars per share) | $ / shares $ 27.09 $ 21.93 $ 27.82
Stock-based compensation      
Total fair value of vested shares (in dollars) | $ $ 1.0 $ 0.8 $ 0.6
Unrecognized compensation expense | $ $ 3.3 $ 0.4 $ 0.9
Period for recognition of unrecognized compensation expense 1 year 10 months 24 days    
Restricted Stock Units | Directors      
Number of Shares      
Granted (in shares) | shares 21,839 28,783 15,918
Weighted Average Grant Date Fair Value      
Granted (in dollars per share) | $ / shares $ 27.36 $ 15.86 $ 26.38
Restricted Stock Units | Employees      
Number of Shares      
Granted (in shares) | shares 176,932 0 4,500
Weighted Average Grant Date Fair Value      
Granted (in dollars per share) | $ / shares $ 27.10   $ 26.92