Derivative Instruments and Hedging Activities - Effect of Derivative Instruments on the Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative instruments and hedging activities
Gain (loss) on derivative instruments	$ (27,184)	$ (6,819)	$ (8,190)	$ 27,304
Non-cash gain (loss) on derivative instruments			(8,190)	27,304
Gain (loss) on derivative instruments	(27,184)	(6,819)	(8,190)	27,304
Derivatives Not Designated as Hedges \| Gain (loss) on derivative instruments
Derivative instruments and hedging activities
Gain (loss) on derivative instruments	11,305	51,045	11,305	88,730
Non-cash gain (loss) on derivative instruments	$ (38,489)	$ (57,864)	$ (19,495)	$ (61,426)

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No definition available.

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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

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- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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