XML 58 R45.htm IDEA: XBRL DOCUMENT v3.19.1
Note 10 - Summary of Stock Options - Valuation Assumption for Employee Stock Purchase Plan (Details)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Expected term (Year) 5 years 5 years
Average volatility 73.00% 76.00%
Risk-free interest rate 2.53% 2.48%
Dividend yield 0.00% 0.00%
2017 Employee Stock Purchase Plan [Member]    
Expected term (Year) 91 days 91 days
Average volatility 74.00% 59.00%
Risk-free interest rate 2.45% 1.39%
Dividend yield 0.00% 0.00%