Derivative Instruments and Hedging Activities (Details 2) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Effect of derivative instruments on the Consolidated Balance Sheet
Fair values of derivative instruments	$ 76,178	$ 137,603
Derivatives Not Designated as Hedges \| Commodity contracts \| Derivative instruments (current assets)
Effect of derivative instruments on the Consolidated Balance Sheet
Fair values of derivative instruments	$ 76,178	$ 137,603

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.

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Balance Type:	debit
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