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Related party transactions (Tables) | 12 Months Ended
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Dec. 31, 2017
Related Party Transactions [Abstract] |
Schedule of related party transactions | A summary of the aforementioned significant related party transactions for the years ended December 31, 2017, 2016 and 2015 is as follows:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015
Net sales to Glencore | $ | 1,198,076 |  |  | $ | 1,178,631 |  |  | $ | 1,867,711 |
Purchases from Glencore | 253,044 |  |  | 231,850 |  |  | 393,158 |
Purchases from BHH | 15,763 |  |  | 10,127 |  |  | 46,592 |

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- Definition Tabular disclosure of related party transactions. Examples of related party transactions include, but are not limited to, transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners and (d) affiliates. + References No definition available. + Details
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