| 
           Major customers 
         | 
        3 Months Ended | 
|---|---|
| 
           Mar. 31, 2014 
         | 
      |
| Major customers | |
| Major customers | 
 9. The Company had one major vendor that accounted for 10.3% of total purchases during the three months ended March 31, 2014. The Company had one major vendor that accounted for 10.4% of total purchases during the three months ended March 31, 2013. The Company had three major customers that accounted for 15.7%, 15.6% and 10.5%, respectively, of its total net sales during the three months ended March 31, 2014. These same customers accounted for 14.2%, 14.1% and 9.3%, respectively, of total net accounts receivable as of March 31, 2014. The Company had three major customers that accounted for 14.5%, 14.4% and 11.3%, respectively, of its total net sales during the three months ended March 31, 2013.  |