Segment information (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Retail [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 606,589	$ 633,273
Bulk [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	778,177	785,901
Services [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 22,474	$ 34,974