XML 44 R41.htm IDEA: XBRL DOCUMENT v3.19.3
Stockholders' Equity (Schedule of Fair Value of Employee Stock Purchase Plan) (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected volatility       65.00%
Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected volatility       67.00%
ESPP [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Expected volatility   65.00%    
Risk-free interest rate, minimum   1.30%   1.30%
Risk-free interest rate, maximum   2.70%   2.70%
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