Inventories, Net - Schedule of Inventories, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory [Line Items]
Parts and supplies	$ 17,386	$ 16,665
Total inventories	63,625	56,524
Raw coal
Inventory [Line Items]
Coal	11,276	6,919
Clean coal
Inventory [Line Items]
Coal	$ 34,963	$ 32,940

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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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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