Derivative Instruments and Hedging Activities - Offsetting Assets (Details) - Commodity Derivative Instruments - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Gross Amounts of Recognized Assets	$ 218,036	$ 208,646
Gross Amounts Offset in the Balance Sheet	(527)	(72)
Net Amounts of Assets Presented in the Balance Sheet	217,509	208,574
Net Amount	$ 217,509	$ 208,574

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 50
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

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