Fair Value - Unobservable Inputs Related to our Level 3 Liabilities (Details) - Level 3 - Natural gas forward contract $ in Thousands	Jun. 30, 2020 USD ($) usdPerMMBtu	Dec. 31, 2019 USD ($) usdPerMMBtu
Derivatives, Fair Value [Line Items]
Derivative liabilities \| $	$ 5,185	$ 6,968
Weighted Average \| Measurement Input, Commodity Forward Price \| Valuation Technique, Discounted Cash Flow
Derivatives, Fair Value [Line Items]
Derivative measurement input	3.07	3.23
Minimum \| Measurement Input, Commodity Forward Price \| Valuation Technique, Discounted Cash Flow
Derivatives, Fair Value [Line Items]
Derivative measurement input	2.25	2.39
Maximum \| Measurement Input, Commodity Forward Price \| Valuation Technique, Discounted Cash Flow
Derivatives, Fair Value [Line Items]
Derivative measurement input	4.62	5.65

Fair value, before effects of master netting arrangements, of a financial liability or 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 liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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