Cost of revenues and general and administrative expenses (Details 1) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 18,709,419	$ 18,682,399
Employee costs [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	8,400,729	8,061,686
Insurance [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	751,541	734,003
Professional fees [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	1,250,634	1,375,965
Directors' fees and expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	845,891	804,110
Depreciation [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	158,404	164,025
NSC project expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	2,884,213	3,011,710
Amortization of intangibles [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	1,340,000	1,363,849
Other [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 3,078,007	$ 3,167,051