Note 14 - Merom Acquisition (Details Textual) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended	9 Months Ended
	Feb. 14, 2022	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022
Operating Expenses		$ 23,803		$ 5,395		$ 75,280	$ (4,098)
Merom Acquisition [Member]
Capacity Payment Reductions	$ 15,000
Purchase Obligation, Total	7,200
Business Acquisition, Purchase of Coal Inventory	17,000
Business Acquisition, Purchase of Coal Inventory, Initial Payment	5,400
Business Acquisition, Transaction Costs	2,900
Contract with Customer, Liability	184,500	98,000				98,000
Contract with Customer, Liability, Revenue Recognized		$ 10,300				$ 63,200
Contract with Customer, Asset, after Allowance for Credit Loss	$ 34,300
Operating Expenses			$ 13,000		$ 30,700
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory			$ 6,800		$ 11,200