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Stock-based Compensation Expense Activity in Non-Performance Based Restricted Stock Awards (Details) - Restricted Stock And Restricted Stock Units
12 Months Ended
Dec. 31, 2020
$ / shares
shares
Shares  
Nonvested, beginning of period (in shares) | shares 272,560
Granted (in shares) | shares 185,261
Vested (in shares) | shares (107,215)
Forfeited (in shares) | shares (23,862)
Nonvested, end of period (in shares) | shares 326,744
Weighted Average Grant Date Fair Value  
Nonvested, beginning of period (in dollars per share) | $ / shares $ 85.98
Granted (in dollars per share) | $ / shares 71.70
Vested (in dollars per share) | $ / shares 80.59
Forfeited (in dollars per share) | $ / shares 89.31
Nonvested, end of period (in dollars per share) | $ / shares $ 79.48