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Derivative Instruments (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Energy contracts and options [Member] | Cost of revenues [Member]
Effects of derivative instruments on the consolidated statements of operations
Amount of Gain (Loss) Recognized on Derivatives	$ (1,248)	$ 361

X

- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

+ Details

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- References

No definition available.

+ Details

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- Details

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