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Stockholders' Equity (Schedule of Fair Value of Employee Stock Purchase Plan) (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected term in years     5 years 1 month 6 days  
ESPP [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected volatility 0.60%   0.60%
Risk-free interest rate      
Risk-free interest rate, minimum 0.80%   0.80%  
Risk-free interest rate, maximum 1.00%   1.00%  
Dividend yield
ESPP [Member] | Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected term in years 6 months   6 months  
ESPP [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected term in years 2 years   2 years