Derivatives - Disclosure of fair Value of derivatives (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative Assets	$ 3,970	$ 2,707
Derivative Liabilities		0
Effect of counterparty netting in derivative liabilities		0
Derivative Asset	$ 3,970	$ 2,707
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets, Current	Other Assets, Current
Derivative Liability		$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Accrued Liabilities, Current	Accrued Liabilities, Current
Net derivatives as classified in the balance sheets	$ 3,970	$ 2,707
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	3,970	2,707
Derivative Liabilities		0
Coal Contract | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	2,869	1,407
Derivative Liabilities		0
Heating oil - diesel purchases | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	$ 1,101	1,300
Derivative Liabilities		$ 0