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Stock-Based Compensation Long-Term Performance Restricted Stock Unit Award Monte Carlo Pricing Model Assumptions (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted, weighted average grant date fair value (in dollars per share) $ 98.94 $ 85.97
Long Term Performance Restricted Stock Award [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 50.50% 37.60%
Risk-free interest rate 0.20% 1.50%
Expected term (years) 2 years 10 months 24 days 1 year 9 months 18 days
Granted, weighted average grant date fair value (in dollars per share) $ 113.75 $ 94.28