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Stock-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2021
Share-based Payment Arrangement [Abstract]  
Summary of Stock Option Activity A summary of stock option activity is as follows:
OptionsNumber of SharesWeighted Average Exercise Price Weighted Average Remaining Contractual Life (Years)Aggregate Intrinsic Value as of December 31, 2021
Outstanding at December 31, 2018417,581 $31.58 
Exercised(211,057)14.65 
Outstanding at December 31, 2019206,524 $48.88 
Exercised(134,930)35.26 
Outstanding at December 31, 202071,594 $74.54 
Exercised(62,322)73.36 
Outstanding at December 31, 20219,272 $82.47 3.98$1,338
Vested9,272 $82.47 3.98$1,338
Ending Exercisable9,272 $82.47 3.98$1,338
Schedule of Stock Options Outstanding and Exercisable
A summary of stock options outstanding and exercisable as of December 31, 2021, is as follows:
 Options OutstandingOptions Exercisable
Exercise PriceSharesWeighted Average Remaining Contractual LifeWeighted Average Exercise PriceSharesWeighted Average Exercise Price
$65.36 - $65.36
1,582 3.15$65.36 1,582 $65.36 
$85.99 - $85.99
7,690 4.1585.99 7,690 85.99 
Summary of Company's Employee and Director Share Grant Activity A summary of the Company’s employee and director share grant activity is as follows:
Restricted Stock GrantsSharesWeighted-Average Grant-Date Fair Value
Unreleased at December 31, 2018223,114 $80.02 
Granted109,081 101.52 
Released(110,724)79.58 
Cancelled(8,863)90.11 
Unreleased at December 31, 2019212,608 $91.62 
Granted95,671 98.81 
Released(94,164)89.43 
Cancelled(5,083)93.16 
Unreleased at December 31, 2020209,032 $95.86 
Granted99,802 132.75 
Released(96,248)91.65 
Cancelled(12,808)113.89 
Unreleased at December 31, 2021199,778 $115.16 
Schedule of Nonvested Performance-based Units Activity A summary of the PSU activity is as follows:
Performance-Based Stock UnitsUnitsWeighted-Average Grant-Date Fair Value
Unvested at December 31, 201858,806 $89.87 
Granted49,334 103.18 
Unvested at December 31, 2019108,140 $95.94 
Granted45,242 129.38 
Released(30,071)$112.16 
Unvested at December 31, 2020123,311 $104.25 
Granted 40,832 138.04 
Released(28,735)$117.19 
Unvested at December 31, 2021135,408 $111.69 
Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Awards A Monte Carlo simulation model was used to calculate the fair value of the TSR Target portion of the PSUs, using the following assumptions:
For the Year Ended December 31,
202120202019
Intrinsic value$30,701$12,266$6,211
Risk-free rate0.22%1.42%2.53%
Volatility28.5%18.4%20.7%
Expected term (in years)2.92.92.8
Dividend yield—%—%—%
Unrecognized compensation cost$8,859$6,406$4,315
Term over which compensation cost recognized (in years)333