Cost of revenues and general and administrative expenses (Details 1) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 19,072,979	$ 18,677,584	$ 14,840,156
Employee costs [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	8,118,231	7,598,829	6,841,274
Insurance [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	761,115	782,013	802,386
Professional fees [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	1,362,332	1,101,938	941,193
Directors' fees and expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	814,208	774,769	754,145
Depreciation [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	167,135	384,045	218,032
NSC project expenses [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	3,011,710	3,011,989	1,976,408
Amortization of intangibles [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	1,363,849	1,410,143	89,896
Other [Member]
Cost of revenues and general and administrative expenses [Line Items]
General and Administrative Expense	$ 3,474,399	$ 3,613,858	$ 3,216,822