Concentration of credit (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member] | Company A [Member]
Concentration Risk [Line Items]
Concentration of credit	0.00%	0.00%
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member] | Company B [Member]
Concentration Risk [Line Items]
Concentration of credit	0.00%	0.00%
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Company A [Member]
Concentration Risk [Line Items]
Concentration of credit	0.00%	0.00%
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Company B [Member]
Concentration Risk [Line Items]
Concentration of credit	0.00%	0.00%