Retirement benefits (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Staff Pension Plans Contribution Matched To Participating Employee Salary	$ 104,400
Pension Expense	$ 376,086	$ 328,084	$ 325,576
Cayman Islands [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	5.00%
Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	6.00%