Note 8 - Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Future Minimum Rental Payments for Operating Leases and Royalty Payments [Table Text Block]

			Coal Lease
			and
(In thousands)	Operating		Royalty
Year Ending December 31,	Leases		Obligations
2019	$	155	$	3,598
2020		117		3,798
2021		99		4,360
2022		41		4,361
2023		—		4,372
Thereafter		—		15,653
Total minimum payments	$	412	$	36,142