Derivative Instruments - Offsetting Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commodity Contract
Offsetting Liabilities [Line Items]
Gross Liabilities	$ (12,051)	$ (36,579)
Gross Amounts Offset	4,233	14,475
Net Liabilities	(7,818)	(22,104)
Cash Collateral Offset	86	1,666
Net Amount Presented	(7,732)	(20,438)
Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(11,213)	(34,628)
Gross Amounts Offset	3,622	13,053
Net Liabilities	(7,591)	(21,575)
Cash Collateral Offset	86	1,632
Net Amount Presented	(7,505)	(19,943)
Non-trading Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(11,139)	(34,434)
Gross Amounts Offset	3,620	12,859
Net Liabilities	(7,519)	(21,575)
Cash Collateral Offset	86	1,632
Net Amount Presented	(7,433)	(19,943)
Trading Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(74)	(194)
Gross Amounts Offset	2	194
Net Liabilities	(72)	0
Cash Collateral Offset	0	0
Net Amount Presented	(72)	0
Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	(838)	(1,951)
Gross Amounts Offset	611	1,422
Net Liabilities	(227)	(529)
Cash Collateral Offset	0	34
Net Amount Presented	(227)	(495)
Non-trading Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	(838)	(1,951)
Gross Amounts Offset	611	1,422
Net Liabilities	(227)	(529)
Cash Collateral Offset	0	34
Net Amount Presented	(227)	(495)
Trading Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	0	0
Gross Amounts Offset	0	0
Net Liabilities	0	0
Cash Collateral Offset	0	0
Net Amount Presented	$ 0	$ 0

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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Fair value, after offset of derivative asset, of 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, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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Fair value of asset associated with 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.

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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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