Quarterly report pursuant to Section 13 or 15(d)

Note 12 - Summary of Stock Options - Valuation Assumption for Employee Stock Purchase Plan (Details)

v3.20.2
Note 12 - Summary of Stock Options - Valuation Assumption for Employee Stock Purchase Plan (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Expected term (Year)   5 years 5 years 5 years
Average volatility   75.00% 73.00% 73.00%
Risk-free interest rate   2.03% 0.45% 2.49%
Dividend yield   0.00% 0.00% 0.00%
2017 Employee Stock Purchase Plan [Member]        
Expected term (Year) 91 days 91 days 91 days 91 days
Average volatility 110.00% 87.00% 117.00% 81.00%
Risk-free interest rate 0.09% 2.43% 0.84% 2.44%
Dividend yield 0.00% 0.00% 0.00% 0.00%