Other Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other income: [Abstract]
Equity income (loss)	$ 55	$ (34)
MSHA reimbursement	100	150
Gain on sale of royalty interests in oil properties		2,500
Miscellaneous	451	1,462
Total Other Income	$ 606	$ 4,078