Derivative Instruments - Fair value (Details) $ in Thousands	Sep. 30, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Fair value of derivative instruments
Current portion of fair value of derivative assets	$ 299,796	$ 73,022
Noncurrent portion of fair value of derivative assets	876,293	1,731,063
Total asset derivatives	1,176,089	1,804,085
Current portion of fair value of derivative liabilities	4,285	203,635
Noncurrent portion of fair value of derivative liabilities	427	234
Total liability derivatives	4,712	203,869
Derivatives not designated as hedges for accounting purposes \| Net fair value of commodity derivative assets position
Fair value of derivative instruments
Current portion of fair value of derivative assets	299,796	73,022
Noncurrent portion of fair value of derivative assets	876,293	1,731,063
Total asset derivatives	1,176,089	1,804,085
Current portion of fair value of derivative liabilities	4,285	203,635
Noncurrent portion of fair value of derivative liabilities	427	234
Total liability derivatives	4,712	203,869
Net derivatives	$ 1,171,377	$ 1,600,216
Derivatives designated as hedges for accounting purposes
Fair value of derivative instruments
Number of derivative instruments held designated as hedges \| item	0	0

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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