Cost of revenues and general and administrative expenses - General and administrative expenses (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 19,348,958	$ 18,709,419
Employee costs [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	9,335,247	8,400,729
Insurance [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	866,457	751,541
Professional fees [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	1,178,621	1,250,634
Directors' fees and expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	969,279	845,891
Depreciation [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	139,817	186,790
NSC project expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	2,343,249	2,855,827
Amortization of intangible assets [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	841,667	1,340,000
Other [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 3,674,621	$ 3,078,007