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Stock-based compensation - Summary of incentive plan for members of management (Details) - Performance Based Shares - $ / shares
6 Months Ended 12 Months Ended
Jun. 30, 2022
Dec. 31, 2021
Restricted Stock    
Non-vested at beginning of period 321,883 358,512
Granted 192,903 191,479
Performance Shares Quantity Adjustment 9,255 54,306
Vested (234,158) (273,974)
Forfeited (295) (8,440)
Non-vested at end of period 289,588 321,883
Weighted-Average Grant Date Fair Value    
Non-vested at beginning of period $ 47.98 $ 41.23
Granted 84.34 69.38
Performance Shares Quantity Adjustment 55.51 54.21
Vested 67.23 55.11
Forfeited 76.85 43.48
Non-vested at end of period $ 56.89 $ 47.98