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Commitments and contingencies (Details) (USD $) In Thousands, unless otherwise specified	159 Months Ended		12 Months Ended	45 Months Ended
	Sep. 30, 2014 MW	Dec. 31, 2013	Dec. 31, 2013 PBGC Agreement [Member]	Dec. 31, 2016 PBGC Forecast [Member] PBGC Agreement [Member]
Environmental Contingencies [Abstract]
Environmental-related accrued liabilities	$ 1,340	$ 999
Environmental remediation expense for Hydrocarbon Recovery Plan	1,033
PBCG Settlement [Abstract]
Pension contributions above required minimum, total				17,400
Pension contributions			6,700
OR Power Agreement [Abstract]
Power currently available under the power purchase agreement (in megawatts)	47.5
Power prepayments	$ 2,267
Labor Commitments [Abstract]
Percentage of U.S. based work force represented by a union (in hundredths)	73.00%
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with	5
Percentage of Grundartangi work force represented by the labor unions (in hundredths)	82.00%
Percentage of Vlissingen work force represented by the labor union (in hundredths)	77.00%

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The number of labor unions representing a group of employees.

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Pursuant to the terms of the settlement agreement with the Pension Benefit Guaranty Corporation, we will make additional contributions (above any minimum required contributions) to our defined benefit pension plans.

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The percentage of a Company's work force, based in the country of domicile, that are subject to collective bargaining agreements.

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The percentage of a Company's Netherlands work force that are subject to collective bargaining agreements

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The percentage of a Company's Icelandic work force that are subject to collective bargaining agreements.

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The power currently available under the power purchase agreement.

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

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The amount of cash or cash equivalents contributed by the entity to fund its pension plans.

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Sum of the carrying amounts as of the balance sheet date of amounts paid in advance for expenses which will be charged against earnings in periods after one year or beyond the operating cycle, if longer.

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