Quarterly report pursuant to Section 13 or 15(d)

Fair value of financial instruments (Details)

v3.19.2
Fair value of financial instruments (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Jun. 30, 2019
Assets, Fair Value   $ 215,000
Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Convertible Notes Receivable [Member]    
Warrants And Rights Outstanding Measurement Inputs Monte Carlo Simulation  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Convertible Notes Receivable [Member]    
Assets, Fair Value $ 837,817  
Investment in Warrants [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member]    
Warrants And Rights Outstanding Measurement Inputs Black-Scholes Option Pricing Model  
Investment in Warrants [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, Fair Value $ 67,000  
Measurement Input, Price Volatility [Member] | Fair Value, Measurements, Recurring [Member] | Convertible Notes Receivable [Member]    
Warrants And Rights Outstanding Measurement Inputs Probability of conversion and interest rates on comparable financial instruments  
Measurement Input, Price Volatility [Member] | Investment in Warrants [Member] | Fair Value, Measurements, Recurring [Member]    
Warrants And Rights Outstanding Measurement Inputs Common stock volatility and discount