Derivative Instruments - Assets and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Commodity derivative assets
Gross amounts on balance sheet	$ 2,578,640	$ 3,163,639
Gross amounts offset on balance sheet	(145,945)	(46,159)
Total asset derivatives	2,432,695	$ 3,117,480
Commodity derivative liabilities
Gross amounts on balance sheet	(3,183)
Gross amounts offset on balance sheet	33
Total liability derivatives	$ (3,150)

Fair value of liability associated with 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.

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