Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Warrant activities (Details)

v3.20.1
Stockholders' Equity - Warrant activities (Details) - Warrants [Member] - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Subsidiary or Equity Method Investee [Line Items]    
Number of shares, Outstanding 2,741,180  
Number of shares, Outstanding 2,741,180 2,741,180
Number of shares, Exercisable 2,656,180  
Weighted average exercise price, Outstanding $ 3.19  
Weighted average exercise price, Outstanding 3.19 $ 3.19
Weighted average exercise price, Exercisable $ 2.79  
Total intrinsic value, Outstanding $ 31,200 $ 111,000
Total intrinsic value, Exercisable $ 31,200  
Weighted average remaining contractual life (years), Outstanding 2 years 5 months 23 days 2 years 8 months 23 days
Weighted average remaining contractual life, Exercisable (years) 1 year 11 months 27 days