Concentrations of credit risk (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Concentrations of credit risk Details
One customer net revenue	89.00%	7.00%
Two customers of net revenue	64.00%	35.00%
Company's net revenue from Customer A	8.00%	8.00%
Two vendor purchased of merchandise	88.00%	7.00%
One vendor sold of merchandise	73.00%	18.00%