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Share-Based Compensation - Performance Share Unit Activity (Details) - Performance Shares Units - $ / shares
6 Months Ended 12 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Shares    
Unvested, Beginning balance (in shares) 58,695  
Granted (in shares) 29,020 24,305
Vested (in shares) 0  
Forfeited (in shares) (5,850)  
Unvested, Ending balance (in shares) 81,865 58,695
Weighted-Average Grant Date Fair Value    
Unvested, Beginning balance (in dollars per share) $ 218.16  
Granted (in dollars per share) 247.49  
Vested (in dollars per share) 0  
Forfeited (in dollars per share) 212.44  
Unvested, Ending balance (in dollars per share) $ 227.90 $ 218.16