Quarterly report pursuant to Section 13 or 15(d)

Fair value of financial instruments - Balances and levels of the assets measured at fair value (Details)

v3.19.3
Fair value of financial instruments - Balances and levels of the assets measured at fair value (Details) - Fair Value, Measurements, Nonrecurring
Dec. 31, 2018
USD ($)
Fair Value, Inputs, Level 1  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value $ 0
Fair Value, Inputs, Level 1 | Investment in Warrants [Member]  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 0
Fair Value, Inputs, Level 1 | Convertible Notes Receivable  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 0
Fair Value, Inputs, Level 2  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 0
Fair Value, Inputs, Level 2 | Investment in Warrants [Member]  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 0
Fair Value, Inputs, Level 2 | Convertible Notes Receivable  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 0
Fair Value, Inputs, Level 3  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 904,317
Fair Value, Inputs, Level 3 | Investment in Warrants [Member]  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value 67,000
Fair Value, Inputs, Level 3 | Convertible Notes Receivable  
Investments, Fair Value Disclosure [Abstract]  
Assets, Fair Value $ 837,317