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v3.3.1.900

Commitments and contingencies (Details) $ in Thousands | Dec. 18, 2015 source | Dec. 31, 2015 USD ($) MW labor_union
--- | --- | ---
OR Power Purchase Agreement Abstract] |  |
Power prepayments | $ |  | $ 1,477
Power currently available under the power purchase agreement (in megawatts) | MW |  | 47.5
Labor Commitments [Abstract] |  |
Percentage of Company's work force represented by a union |  | 63.00%
Percentage of Grundartangi work force represented by the labor unions |  | 84.00%
Number of labor unions under new agreement | labor_union |  | 5
Percentage of Vlissingen work force represented by the labor union |  | 100.00%
Percentage of U.S. based work force represented by a union |  | 53.00%
South Carolina Public Service Authority [Member] |  |
Short-term Agreement for Power Supply [Line Items] |  |
Operating capacity under agreement, percentage | 50.00% |
Number of power sources | source | 2 |
Power agreement, power supply from source one, percentage | 25.00% |
Power agreement, power supply from source two, percentage | 75.00% |
Agreement termination notice period | 60 days |

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