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Note 7 - Commitments and Contingencies (Details) - USD ($) $ in Millions					3 Months Ended
	Jul. 20, 2023	Mar. 04, 2022	Jul. 16, 2021	Jul. 15, 2021	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
COMMITMENTS AND CONTINGENCIES
Royalty expense					$ 6.8	$ 9.0
Compensatory damages	$ 7.7	$ 1.8	$ 25.0	$ 7.7
Award to cover inconvenience and aggravation	$ 25.0
Accrued amount					1.4		$ 0.8
Surety Bond
COMMITMENTS AND CONTINGENCIES
Asset Retirement Obligation					30.2
Take-or-pay Purchase Commitments
COMMITMENTS AND CONTINGENCIES
Commitment					19.4
Total commitment					$ 30.7
Commitment term					4 years
Environmental
COMMITMENTS AND CONTINGENCIES
Environmental liabilities					$ 0.0