Inventories, net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Coal	$ 87,684	$ 69,064
Raw materials, parts, supplies and other, net	29,879	28,837
Total inventories, net	$ 117,563	$ 97,901

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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