Self Insurance	12 Months Ended
Dec. 31, 2019
Self Insurance [Abstract]
Self Insurance	(13) SELF INSURANCE We self-insure our underground mining equipment. Such equipment is allocated among 10 mining units dispersed over 22 miles. The historical cost of such equipment was approximately $273 million and $255 million as of December 31, 2019 and December 31, 2018, respectively. As of February 29, with the closure of the Carlisle Mine, we are now operating seven mining units dispersed over 10 miles. Restricted cash of $4.5 million and $4.6 million as of December 31, 2019, and December 31, 2018, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.

(13) SELF INSURANCE

We self-insure our underground mining equipment. Such equipment is allocated among 10 mining units dispersed over 22 miles. The historical cost of such equipment was approximately $273 million and $255 million as of December 31, 2019 and December 31, 2018, respectively. As of February 29, with the closure of the Carlisle Mine, we are now operating seven mining units dispersed over 10 miles.

Restricted cash of $4.5 million and $4.6 million as of December 31, 2019, and December 31, 2018, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments.