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Employee Benefits and Share-Based Compensation - Assumptions Used to Value ESPP Shares (Details) - ESPP shares available for future issuance - 1997 Plan
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility (minimum) 28.80% 27.40%
Expected volatility (maximum) 45.60% 53.50%
Risk-free interest rate (minimum) 0.10% 0.10%
Risk-free interest rate (maximum) 1.50% 2.60%
Dividend yield 0.00% 0.00%
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 6 months 6 months
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 2 years 2 years