Note 4 - Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Property, plant and equipment, net	$ 243,870	$ 218,646
Computer Equipment [Member]
Property, plant and equipment, gross	778	780
Furniture and Fixtures [Member]
Property, plant and equipment, gross	610	610
Leasehold Improvements [Member]
Property, plant and equipment, gross	101	101
Excluding Construction in Progress [Member]
Property, plant and equipment, gross	1,489	1,491
Less: accumulated depreciation	(1,044)	(1,006)
Property, plant and equipment, net	445	485
Construction in Progress [Member]
Property, plant and equipment, gross	243,425	218,161
Construction in Progress [Member] | Rio Grande [Member]
Property, plant and equipment, gross	222,408	197,144
Construction in Progress [Member] | Rio Bravo [Member]
Property, plant and equipment, gross	$ 21,017	$ 21,017