Inventories (Schedule of Inventory Components) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Coal	$ 4,642	$ 11,411
Supplies	44,004	42,009
Total Inventories	$ 48,646	$ 53,420

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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-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-02.6(a))
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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section 45
-Paragraph 1
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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of products used directly or indirectly in the manufacturing or production process, which may or may not become part of the final product. May also include items used in the storage, presentation or transportation of physical goods.

+ References

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-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section S99
-Paragraph 2
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