Income taxes (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Summary of reconciliation of the provision for income taxes at the statutory rate to the reported provision for income taxes
Income Tax computed at statutory rate	$ 765,367	$ 1,016,323
State tax, net of federal benefit	12,344	21,637
Loss attributable to noncontrolling interest	8,746	9,581
Share based compensation	85,109	66,600
Other, permanent adjustments	(59,247)	(86,666)
Tax credits and prior year tax adj.	3,493	27,603
Provision for income taxes	$ 815,812	$ 1,055,078
Income Tax computed at statutory rate, percentage	34.00%	34.00%
State tax, net of federal benefit, percentage	0.50%	0.70%
Loss attributable to noncontrolling interest, percentage	0.40%	0.30%
Share based compensation, percentage	3.70%	2.20%
Other, permanent adjustments, percentage	(2.60%)	(2.90%)
Tax credits and prior year tax adj., percentage	0.20%	1.00%
Provision for income taxes, percentage	36.20%	35.30%