Basis of presentation, summary of significant accounting policies (Schedule of Antidilutive Securities) (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares not included in the computation of EPS	4,588,349	3,829,373
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	3,354,257	3,574,257
Option 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
Escrow shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares not included in the computation of EPS		200,000
Unvested restricted stock awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares not included in the computation of EPS	1,217,893	38,917
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	4,199	4,199