Cash and cash equivalents (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash and Cash Equivalents [Line Items]
Bank accounts	$ 22,058,252	$ 33,523,679
Short term deposits	11,568,264	368,976
Total cash and cash equivalents	33,626,516	33,892,655	37,624,179	46,130,237
United States dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	10,484,207	7,139,591
Short term deposits	527,580	368,976
Cayman Islands dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	5,275,615	10,907,483
Bahamian dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	3,090,021	13,308,338
Short term deposits	11,040,684	0
Belize dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	3,055,990	2,007,243
Bermudian dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	6,759	11,930
Mexican Peso [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	11,227	14,198
Euro [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	22,731	14,264
Singapore dollar [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	27,644	8,190
Indonesian Rupiah [Member]
Cash and Cash Equivalents [Line Items]
Bank accounts	$ 84,058	$ 112,442