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Self Insurance	3 Months Ended
Self Insurance	Mar. 31, 2017
Self Insurance [Abstract]
Self Insurance	(5)Self-Insurance We self-insure our underground mining equipment. Such equipment is allocated among ten mining units spread out over 18 miles. The historical cost of such equipment is approximately $247 million. Restricted cash of $3.1 million represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.