Derivatives - Disclosure of fair Value of derivatives (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative Assets	$ 998	$ 2,707
Derivative Liabilities	(165)
Effect of counterparty netting in derivative liabilities	0
Derivative Asset	$ 998	$ 2,707
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets, Current	Other Assets, Current
Derivative Liability	$ (165)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Accrued Liabilities, Current	Accrued Liabilities, Current
Net derivatives as classified in the balance sheets	$ 833	$ 2,707
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	998	2,707
Derivative Liabilities	(165)
Coal | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets		1,407
Derivative Liabilities	(165)
Heating oil - diesel purchases | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	998	$ 1,300
Derivative Liabilities	$ 0