Note 4 - Miscellaneous Other (Loss) Income (Details Textual) T in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) T $ / T	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) T	Jun. 30, 2020 USD ($)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts, Total	$ (20,437,000)	$ 0	$ (20,437,000)	$ (0)
Coal Contract [Member]
Derivative, Nonmonetary Notional Amount, Mass (US Ton) | T	2		2
Underlying, Derivative Volume (in USD per US Ton) | $ / T	79.34
Unrealized Gain (Loss) on Derivatives and Commodity Contracts, Total	$ (20,437)