Quarterly report pursuant to Section 13 or 15(d)

Basis of presentation, summary of significant accounting policies (Schedule of Antidilutive Securities) (Details)

v3.21.2
Basis of presentation, summary of significant accounting policies (Schedule of Antidilutive Securities) (Details) - shares
 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares not included in the computation of EPS 650,044 4,883,911
Warrants to purchase common stock [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares not included in the computation of EPS 3,554,257
Options to purchase common stock [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares not included in the computation of EPS 12,000 12,000
Unvested restricted stock awards [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares not included in the computation of EPS 635,845 1,313,455
Convertible Series B Preferred Shares [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares not included in the computation of EPS 2,199 4,199