Note 4 - Other Long-term Assets (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Schedule of Other Assets, Noncurrent [Table Text Block]

	June 30,		December 31,
	2021		2020
Advanced coal royalties	$	6,573	$	6,449
Other		1,752		1,809
Total other assets	$	8,325	$	8,258