Income taxes (Details 4) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Operating loss carryforwards
Valuation allowance	$ 29,238,264	$ 26,452,590
Federal
Operating loss carryforwards
Net operating loss carryforwards	70,500,000
State, primarily New York State
Operating loss carryforwards
Net operating loss carryforwards	$ 24,800,000