Other Income (Schedule of Other Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other income:
MSHA reimbursement	$ 503	$ 386
Other	195	381
Other income	77	998
Savoy [Member]
Other income:
Equity income (loss)		212
Loss on disposal of equity method investment	(538)
Sunrise Energy [Member]
Other income:
Equity income (loss)	$ (83)	$ 19