Derivative Instruments - Narrative (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2020 USD ($) Bcf	Sep. 30, 2020 USD ($) MMBbls	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) Bcf
Derivative Instruments, Gain (Loss)
Maximum additional collateral as percentage of derivative liability			100.00%
Aggregate fair value of derivative instruments with credit-risk related contingencies	$ 228,800,000	$ 228,800,000	$ 228,800,000	$ 0
Collateral posted	142,000,000.0	142,000,000.0	142,000,000.0	0
Asset derivative instruments, at fair value	503,648,000	503,648,000	503,648,000	812,664,000
Liability derivative instrument, at fair value	894,618,000	894,618,000	894,618,000	312,696,000
Natural Gas Liquid Instrument
Derivative Instruments, Gain (Loss)
Aggregate fair value of derivative instruments with credit-risk related contingencies	0	0	0	0
Asset derivative instruments, at fair value	102,500,000	102,500,000	102,500,000	12,600,000
Commodity derivatives
Derivative Instruments, Gain (Loss)
Asset derivative instruments, at fair value	503,648,000	503,648,000	503,648,000	812,664,000
Liability derivative instrument, at fair value	$ 894,618,000	$ 894,618,000	$ 894,618,000	$ 312,696,000
Cash flow hedging \| Commodity derivatives
Derivative Instruments, Gain (Loss)
Volume of derivative instruments (in Bcf, Mbbls)	1,659	1,723		1,644

The upper limit of the percentage of derivative liability that the entity may be required to post with counterparties.

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Fair value, before 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 elected not to be offset. Excludes assets not subject to a master netting arrangement.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Nominal volume used to calculate payments on a derivative instrument.

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No definition available.

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