Segment information (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Retail [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 587,726	$ 590,040
Bulk [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	827,389	794,725
Services [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization	$ 239,707	$ 22,474

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Name:	us-gaap_DepreciationDepletionAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration