Derivatives (Schedule of Price Risk Derivatives) (Details) - 2021 T in Thousands	3 Months Ended
Mar. 31, 2021 T
Coal sales
Derivative [Line Items]
Derivatives held (in tons)	320
Coal purchases
Derivative [Line Items]
Derivatives held (in tons)	62

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.

No definition available.

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