Segment information (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Retail [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 567,833	$ 583,551	$ 1,714,928	$ 1,755,123
Bulk [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	811,741	815,994	2,480,314	2,419,509
Services [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 451,267	$ 28,976	$ 1,213,282	$ 73,924