Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Assets	$ 6,104	$ 3,245
Derivative Liabilities	(2,203)	(2,399)
Effect of counterparty netting in derivative assets	(1,890)	(2,392)
Effect of counterparty netting in derivative liabilities	1,890	2,392
Derivative Asset	4,214	853
Derivative Liability	(313)	(7)
Net derivatives as classified in the balance sheets	3,901	846
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	6,104	3,245
Derivative Liabilities	(2,203)	(2,399)
Not Designated as Hedging Instrument | Coal held for trading purposes, exchange traded swaps and futures
Derivative [Line Items]
Derivative Assets		1,914
Derivative Liabilities	0	(1,595)
Coal | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liabilities	0
Coal | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	4,885	1,094
Derivative Liabilities	(2,203)	(804)
Heating oil - diesel purchases | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	1,219	$ 237
Derivative Liabilities	$ 0