Derivatives (Details 3) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gain (loss) on derivative
Gains or losses that were excluded from the assessment of the effectiveness of fair value hedges	$ 0	$ 0	$ 0
Derivative, credit-risk related contingent features
Net liability position	111,700,000
Collateral posted	89,400,000
Additional assets required to be posted should credit-risk contingent feature be triggered	22,300,000
Derivatives designated as hedging instruments \| Fair value hedges
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Hedge	132,199,000	2,685,000	(20,869,000)
Realized and Unrealized Gain (Loss) on Hedged Item	(150,943,000)	3,059,000	24,510,000
Derivatives designated as hedging instruments \| Fair value hedges \| Commodity contracts \| Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Hedge			265,000
Realized and Unrealized Gain (Loss) on Hedged Item			(201,000)
Derivatives designated as hedging instruments \| Fair value hedges \| Commodity contracts one \| Cost of revenue.
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Hedge			(1,417,000)
Realized and Unrealized Gain (Loss) on Hedged Item			739,000
Derivatives designated as hedging instruments \| Fair value hedges \| Commodity contracts two \| Cost of revenue.
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Hedge	132,199,000	2,685,000	(19,717,000)
Realized and Unrealized Gain (Loss) on Hedged Item	(150,943,000)	3,059,000	23,972,000
Derivatives not designated as hedging instruments
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	83,641,000	15,976,000	13,645,000
Derivatives not designated as hedging instruments \| Commodity contracts \| Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	64,485,000	25,420,000	14,967,000
Derivatives not designated as hedging instruments \| Commodity contracts \| Cost of revenue.
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	2,239,000	(5,391,000)	3,333,000
Derivatives not designated as hedging instruments \| Foreign currency contracts \| Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	4,286,000	(55,000)	(2,384,000)
Derivatives not designated as hedging instruments \| Foreign currency contracts \| Other income (expense), net
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	$ 12,631,000	$ (3,998,000)	$ (2,271,000)

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

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Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

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-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

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-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (c)

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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Section 50

-Paragraph 1

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