Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Inventories
Coal	$ 99,776	$ 99,174
Repair parts and supplies	150,089	145,087
Inventories	249,865	244,261
Allowance for slow-moving and obsolete inventories	$ 1,600	$ 1,600

Carrying amount as of the balance sheet date of coal, which is a combustible rock or minerals which are extracted from the ground and used as fuel.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date for elements of machinery or equipment held for the purpose of replacing similar parts in the course of repair or maintenance.

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Amount of valuation reserve for inventory.

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