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Incentive Plan - Summary of Option Activity (Details) - $ / shares
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Number of Shares      
Number of shares, outstanding at beginning of year (in shares) 2,424,032 2,340,842 2,489,314
Number of shares, granted (in shares) 699,651 461,407 135,107
Number of shares, assumed in acquisition (in shares) 0 0 491,248
Number of shares, exercised (in shares) (213,506) (227,189) (765,624)
Number of shares, forfeited (in shares) (6,357) (149,158) (9,203)
Number of shares, expired (in shares) (64,953) (1,870) 0
Number of shares, outstanding at end of year (in shares) 2,838,867 2,424,032 2,340,842
Number of shares, options exercisable at end of year (in shares) 1,596,927 1,612,946 1,604,576
Weighted Average Exercise Price      
Weighted average exercise price, outstanding at beginning of year (in dollars per share) $ 19.80 $ 18.25 $ 16.91
Weighted average exercise price, granted (in dollars per share) 20.44 25.20 27.39
Weighted average exercise price, assumed in acquisition (in dollars per share) 0 0 21.92
Weighted average exercise price, exercised (in dollars per share) 9.50 11.24 17.69
Weighted average exercise price, forfeited (in dollars per share) 21.26 24.71 28.42
Weighted average exercise price, expired (in dollars per share) 22.51 29.59 0
Weighted average exercise price, outstanding at end of year (in dollars per share) $ 20.67 $ 19.80 $ 18.25