Derivative Instruments - Fair value (Details) $ in Thousands	Jun. 30, 2020 USD ($) item	Dec. 31, 2019 USD ($) item
Fair value of derivative instruments
Current portion of fair value of derivative assets	$ 521,459	$ 422,849
Noncurrent portion of fair value of derivative assets	103,514	333,174
Current portion of fair value of derivative liabilities	3,652	6,721
Noncurrent portion of fair value of derivative liabilities	2,558	3,519
Commodity derivative
Fair value of derivative instruments
Total asset derivatives	624,973	756,023
Total liability derivatives	6,210	10,240
Derivatives not designated as hedges for accounting purposes
Fair value of derivative instruments
Total asset derivatives	624,973	756,023
Total liability derivatives	6,210	10,240
Net derivatives	618,763	745,783
Derivatives not designated as hedges for accounting purposes \| Commodity derivative
Fair value of derivative instruments
Current portion of fair value of derivative assets	521,459	422,849
Noncurrent portion of fair value of derivative assets	103,514	333,174
Current portion of fair value of derivative liabilities	3,652	6,721
Noncurrent portion of fair value of derivative liabilities	2,558	$ 3,519
Derivatives not designated as hedges for accounting purposes \| Commodity derivative \| VIE, Martica
Fair value of derivative instruments
Total liability derivatives	$ 2,000
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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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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