Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Activity (Details)

v3.21.2
Share-Based Compensation - Activity (Details) - USD ($)
3 Months Ended 6 Months Ended
Feb. 16, 2021
Feb. 17, 2020
Feb. 18, 2019
Mar. 31, 2021
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Stock Options, Number of Shares              
Converted/Exercised (in shares)       (51,915)      
Stock options, additional disclosures              
Weighted average remaining contractual term for vested stock options         6 years 3 months 18 days    
Unrecognized share-based compensation expense              
Restricted stock awards, Unrecognized compensation expense         $ 12,153,000    
Restricted stock awards, Weighted average remaining vesting period         1 year 3 months 18 days    
Stock options, Unrecognized compensation expense         $ 2,479,000    
Stock options, Weighted average remaining vesting period         1 year 2 months 12 days    
Total unrecognized compensation expense related to unvested awards         $ 14,632,000    
Restricted Stock Awards              
Restricted Stock Awards, Number of Shares              
Balance at beginning of period (in shares)       324,800 324,800    
Granted (in shares)         60,100    
Converted/Exercised (in shares)         (143,100)    
Forfeited/Expired (in shares)         (9,000.0)    
Balance at end of period (in shares)         232,800    
Restricted Stock Awards, Weighted Average Grant Date Fair Value Per Share              
Balance at beginning of period (in dollars per share)       $ 87.79 $ 87.79    
Granted (in dollars per share)         246.26    
Converted/Exercised (in dollars per share)         81.34    
Forfeited/Expired (in dollars per share)         89.62    
Balance at end of period (in dollars per share)         $ 113.04    
Assumptions used to estimate the fair values of the awards granted:              
Measurement period (years)         2 years 10 months 13 days 2 years 10 months 17 days  
Risk free interest rate (as a percent)         0.22% 1.40%  
Dividend yield (as a percent)         0.00% 0.00%  
Estimated fair value of market-based RSAs at grant date (in dollars per share)         $ 298.66 $ 158.24  
Restricted Stock Awards | Performance-based conditions              
Restricted stock awards, additional disclosures              
Grant date fair value $ 2,564,000 $ 2,665,000 $ 2,138,000        
Restricted Stock Awards | Performance-based conditions | Payout Range-0%              
Restricted stock awards, additional disclosures              
Payout range (as a percent) 0.00% 0.00% 0.00%        
Restricted Stock Awards | Performance-based conditions | Payout Range-25%              
Restricted stock awards, additional disclosures              
Payout range (as a percent) 25.00% 25.00% 25.00%        
Related expenses $ 641,000 $ 666,000 $ 535,000        
Restricted Stock Awards | Performance-based conditions | Payout Range-100%              
Restricted stock awards, additional disclosures              
Payout range (as a percent) 100.00% 100.00% 100.00%        
Related expenses $ 2,564,000 $ 2,665,000 $ 2,138,000        
Restricted Stock Awards | Performance-based conditions | Payout Range-200%              
Restricted stock awards, additional disclosures              
Payout range (as a percent) 200.00% 200.00% 200.00%        
Related expenses $ 5,128,000 $ 5,330,000 $ 4,276,000        
RSAs granted February 19, 2018 | Performance-based conditions              
Restricted stock awards, additional disclosures              
Cumulative period of achievement       3 years      
Cumulative achievement percentage       200.00%      
Total compensation expense recognized over the performance period, net of forfeitures       $ 3,700,000      
Stock Options              
Stock Options, Number of Shares              
Balance at beginning of period (in shares)       239,700 239,700    
Granted (in shares)         24,100    
Converted/Exercised (in shares)         (51,900)    
Balance at end of period (in shares)         211,900    
Stock Options, Weighted Average Grant Date Fair Value Per Share              
Balance at beginning of period (in dollars per share)       $ 24.33 $ 24.33    
Granted (in dollars per share)         89.59    
Converted/Exercised (in dollars per share)         21.97    
Balance at end of period (in dollars per share)         32.33    
Stock Options, Weighted Average Exercise Price Per Share              
Balance at beginning of period (in dollars per share)       $ 68.86 68.86    
Granted (in dollars per share)         214.58    
Converted/Exercised (in dollars per share)         61.30    
Balance at end of period (in dollars per share)         $ 87.28    
Stock options, additional disclosures              
Aggregate intrinsic value         $ 23,809,900   $ 27,612,100
Converted/Exercised aggregate intrinsic value         $ 7,039,900    
Exercisable, Number of shares         115,700    
Exercisable, Weighted Average Grant Date Fair Value Per Share         $ 20.97    
Exercisable Weighted Average Exercise Price Per Share         $ 57.86    
Exercisable, Aggregate Intrinsic Value         $ 16,187,500    
Assumptions used to estimate the fair values of the awards granted:              
Risk free interest rate (as a percent)         0.76% 1.53%  
Expected volatility using historical return volatility and implied volatility (as a percent)         43.29% 31.50%  
Expected life (in years)         6 years 6 years  
Dividend yield (as a percent)         0.00% 0.00%  
Estimated fair value of market-based RSAs at grant date (in dollars per share)         $ 89.59 $ 39.49