Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Assets	$ 11,001	$ 3,245
Derivative Liabilities	(39,562)	(2,399)
Effect of counterparty netting in derivative assets	(11,001)	(2,392)
Effect of counterparty netting in derivative liabilities	11,001	2,392
Derivative Asset		853
Derivative Liability	(28,561)	(7)
Net derivatives as classified in the balance sheets	(28,561)	846
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	11,001	3,245
Derivative Liabilities	(39,562)	(2,399)
Not Designated as Hedging Instrument \| Coal Contract
Derivative [Line Items]
Derivative Assets	7,768	1,914
Derivative Liabilities	(7,688)	(1,595)
Coal Contract \| Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liabilities		0
Coal Contract \| Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	3,233	1,094
Derivative Liabilities	$ (31,874)	(804)
Heating oil - diesel purchases \| Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets		237
Derivative Liabilities		$ 0

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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 values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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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 the 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 not subject to a master netting arrangement and not elected to be offset.

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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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