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Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) - Not Designated as Hedging Instrument - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Coal Contract | Change in fair value of coal derivatives and coal trading activities, net        
Derivative Instruments, Gain (Loss) [Line Items]        
Unrealized Gain (Loss) on Derivatives $ (1,877) $ (8,762) $ (17,396) $ (9,290)
Coal Contract | Other operating (income) expense, net        
Derivative Instruments, Gain (Loss) [Line Items]        
Realized Gain (Loss) on Derivatives (17,385) $ (651) (26,459) $ (513)
Heating oil - diesel purchases | Other operating (income) expense, net        
Derivative Instruments, Gain (Loss) [Line Items]        
Heating oil realized and unrealized gains and losses $ 6,704   $ 13,532