Energy Related Inventory, Coal, Historical Annual Delivery

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Maximum Contingent Annual Payment to Acquire Mineral Rights

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Maximum Contingent Total Payment to Acquire Mineral Rights

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Number Of Gross Acres Acquired

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Number Of Net Royalty Acres Acquired

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Possible Additional Payment Received From Contract Termination

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Amount of investment in equity security without readily determinable fair value.

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Gain (loss) related to the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one party, or a failure to perform.

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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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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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The cash outflow from the acquisition of a mineral right which is the right to extract a mineral from the earth or to receive payment, in the form of royalty, for the extraction of minerals.

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Nature of Operations and Basis of Presentation (Narrative) (Details) $ in Thousands, T in Millions		3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 17, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($) a	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) operatingSegment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 T
Long-term Purchase Commitment [Line Items]
Number of operating segments \| operatingSegment					3
Contract termination settlement		$ 10,333		$ 0	$ 10,333	$ 0
Coal Mining \| Midwest AgEnergy
Long-term Purchase Commitment [Line Items]
Investment		5,000			5,000
Coal Mining \| Falkirk
Long-term Purchase Commitment [Line Items]
Contract termination settlement	$ 14,000
Coal Mining \| Falkirk \| Maximum
Long-term Purchase Commitment [Line Items]
Possible additional payment from cancelation of agreement		8,000			8,000
Coal Mining \| Falkirk \| Minimum
Long-term Purchase Commitment [Line Items]
Possible additional payment from cancelation of agreement		$ 2,000			2,000
Coal Mining \| Falkirk \| Long-term Contract with Customer
Long-term Purchase Commitment [Line Items]
Historical lignite coal annual delivery \| T							0.3
Coal Mining \| Bisti
Long-term Purchase Commitment [Line Items]
Contract termination settlement					$ 10,300
Minerals Management \| Eagle Ford Basin
Long-term Purchase Commitment [Line Items]
Gross acres acquired \| a			14,100
Net royalty acres acquired \| a			1,700
Payments to acquire royalty interests			$ 4,700
Additional payment to acquire assets			600
Total additional payment to acquire assets			1,200
Minerals Management \| Delaware Basin
Long-term Purchase Commitment [Line Items]
Payments to acquire royalty interests			$ 300