Note 6 - Equity - Common Stock (Details)		3 Months Ended
	Jun. 12, 2023 Vote D	Jun. 30, 2022 $ / T	Jun. 21, 2023
Class of Stock [Line Items]
Percent of royalty fee income		3.00%
Price per ton of coal processed at preparation plants | $ / T		5.00
Price per ton of loaded coal at rail load-out facilities | $ / T		2.50
Percentage dividend from financial performance of carbon		20
Threshold trading days volume weighted average price | D	20
Class A Common Stock
Class of Stock [Line Items]
Number of votes per common share | Vote	1
Class B Common Stock
Class of Stock [Line Items]
Distribution ratio			0.2
Number of votes per common share | Vote	1