Self Insurance	6 Months Ended
Jun. 30, 2019
Self Insurance [Abstract]
Self Insurance	(8)SELF-INSURANCE We self-insure our underground mining equipment. Such equipment is allocated among ten mining units dispersed over 22 miles. The historical cost of such equipment was approximately $266 million and $255 million as of June 30, 2019 and December 31, 2018, respectively. Restricted cash of $4.6 million and $4.6 million as of June 30, 2019 and December 31, 2018, 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 dispersed over 22 miles. The historical cost of such equipment was approximately $266 million and $255 million as of June 30, 2019 and December 31, 2018, respectively.

Restricted cash of $4.6 million and $4.6 million as of June 30, 2019 and December 31, 2018, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.