Note 10 - Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

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

			Coal Lease
			and
	Operating		Royalty
Year Ending December 31,	Leases		Obligations
2018	$	158,618	$	2,016,378
2019		117,148		3,656,564
2020		74,623		3,155,064
2021		60,448		3,115,064
2022		15,112		3,012,064
Thereafter		—		21,145,220
Total minimum payments	$	425,949	$	36,100,354