Self-Insurance	3 Months Ended
Mar. 31, 2018
Self-Insurance [Abstract]
Self-Insurance	(8)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 was approximately $261 million and $258 million for the periods ended March 31, 2018 and December 31, 2017, respectively. Restricted cash of $4.1 million and $3.8 million for the periods ended March 31, 2018 and December 31, 2017, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.

(8)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 was approximately $261 million and $258 million for the periods ended March 31, 2018 and December 31, 2017, respectively.

Restricted cash of $4.1 million and $3.8 million for the periods ended March 31, 2018 and December 31, 2017, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.