XML 33 R22.htm IDEA: XBRL DOCUMENT v3.20.2
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - STOCK OPTIONS AND EMPLOYEE STOCK PURCHASE PLAN (Details)
6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Stock Options    
Stock-Based Compensation    
Vesting period of awards 4 years  
Assumptions used to estimate fair value of awards    
Dividend yield (as a percent) 0.00% 0.00%
Expected volatility range, minimum (as a percent) 78.10% 80.20%
Expected volatility range, maximum (as a percent) 79.00% 98.00%
Risk-free interest rate range, minimum (as a percent) 0.37% 1.79%
Risk-free interest rate range, maximum (as a percent) 1.62% 2.56%
Expected term range 5 years 3 months  
Stock Options | Minimum    
Assumptions used to estimate fair value of awards    
Expected term range   5 years 3 months
Stock Options | Maximum    
Assumptions used to estimate fair value of awards    
Expected term range   6 years 5 months 8 days
Employee Stock Purchase Plan    
Assumptions used to estimate fair value of awards    
Dividend yield (as a percent) 0.00% 0.00%
Expected volatility range, minimum (as a percent) 47.80% 133.30%
Expected volatility range, maximum (as a percent) 56.40% 165.30%
Risk-free interest rate range, minimum (as a percent) 1.56% 2.56%
Risk-free interest rate range, maximum (as a percent) 1.57% 2.63%
Employee Stock Purchase Plan | Minimum    
Assumptions used to estimate fair value of awards    
Expected term range 6 months 6 months
Employee Stock Purchase Plan | Maximum    
Assumptions used to estimate fair value of awards    
Expected term range 12 months 12 months