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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, 2019
$ / shares
shares
Shares  
Nonvested, beginning of period (in shares) | shares 257,518
Granted (in shares) | shares 131,365
Vested (in shares) | shares (89,548)
Forfeited (in shares) | shares (26,775)
Nonvested, end of period (in shares) | shares 272,560
Weighted Average Grant Date Fair Value  
Nonvested, beginning of period (in dollars per share) | $ / shares $ 85.44
Granted (in dollars per share) | $ / shares 79.27
Vested (in dollars per share) | $ / shares 73.61
Forfeited (in dollars per share) | $ / shares 89.23
Nonvested, end of period (in dollars per share) | $ / shares $ 85.98