Note 6 - Equity - Common Stock (Details)			3 Months Ended
	Jun. 21, 2023 USD ($)	Jun. 12, 2023 D Vote	Jun. 30, 2022 $ / T
Equity
Percent of royalty fee income			3.00%
Price per ton of coal processed at preparation plants			5
Price per ton of loaded coal at rail load-out facilities			2.5
Threshold trading days volume weighted average price | D		20
Class A Common Stock
Equity
Number of votes per common share | Vote		1
Class B Common Stock
Equity
Distribution ratio	0.2
Number of votes per common share	1	1
Percentage dividend from financial performance of carbon			20