Derivative Instruments - Offsetting Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commodity Contract
Offsetting Assets [Line Items]
Gross Assets	$ 420	$ 1,073
Gross Amounts Offset	(109)	(503)
Net Assets	311	570
Cash Collateral Offset	0	0
Net Amount Presented	311	570
Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	420	740
Gross Amounts Offset	(109)	(276)
Net Assets	311	464
Cash Collateral Offset	0	0
Net Amount Presented	311	464
Non-trading Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	308	570
Gross Amounts Offset	(105)	(275)
Net Assets	203	295
Cash Collateral Offset	0	0
Net Amount Presented	203	295
Trading Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	112	170
Gross Amounts Offset	(4)	(1)
Net Assets	108	169
Cash Collateral Offset	0	0
Net Amount Presented	108	169
Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	0	333
Gross Amounts Offset	0	(227)
Net Assets	0	106
Cash Collateral Offset	0	0
Net Amount Presented	0	106
Non-trading Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	0	333
Gross Amounts Offset	0	(227)
Net Assets	0	106
Cash Collateral Offset	0	0
Net Amount Presented	0	106
Trading Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	0	0
Gross Amounts Offset	0	0
Net Assets	0	0
Cash Collateral Offset	0	0
Net Amount Presented	$ 0	$ 0

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Fair value of liability associated with 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.

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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, after offset of derivative liability, of 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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