Note 8 - Property, Plant and Equipment and Construction-in-process - Activity in Construction and Development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Balance	$ 893,198
Write off of unsuccessful exploration costs	(3,733)	$ (828)	$ 0
Balance	814,967	893,198
Projects Under Exploration and Development [Member]
Balance	95,268	50,702	51,528
Cost incurred during the year	70,667	44,566	2,680
Transfer of projects under exploration and development to projects under construction			(3,506)
Write off of unsuccessful exploration costs	(3,459)
Balance	162,476	95,268	50,702
Projects Under Exploration and Development [Member] | Up-front Bonus Lease Costs [Member]
Balance	5,335	5,335	5,347
Cost incurred during the year	0	0	0
Transfer of projects under exploration and development to projects under construction			(12)
Write off of unsuccessful exploration costs	0
Balance	5,335	5,335	5,335
Projects Under Exploration and Development [Member] | Exploration and Development Costs [Member]
Balance	89,230	44,664	45,478
Cost incurred during the year	70,667	44,566	2,680
Transfer of projects under exploration and development to projects under construction			(3,494)
Write off of unsuccessful exploration costs	(3,459)
Balance	156,438	89,230	44,664
Projects Under Exploration and Development [Member] | Interest Capitalized [Member]
Balance	703	703	703
Cost incurred during the year	0	0	0
Transfer of projects under exploration and development to projects under construction			0
Write off of unsuccessful exploration costs	0
Balance	703	703	703
Construction in Progress [Member]
Balance	797,930	670,781	427,787
Cost incurred during the year	488,603	495,526	413,842
Transfer of projects under exploration and development to projects under construction			3,506
Write off of unsuccessful exploration costs	(993)
Balance	652,491	797,930	670,781
Transfer of completed projects to property, plant and equipment	(633,049)	(368,377)	(174,354)
Construction in Progress [Member] | Up-front Bonus Lease Costs [Member]
Balance	11,156	39,156	39,144
Cost incurred during the year	0	0	0
Transfer of projects under exploration and development to projects under construction			12
Write off of unsuccessful exploration costs	0
Balance	11,156	11,156	39,156
Transfer of completed projects to property, plant and equipment	0	(28,000)	0
Construction in Progress [Member] | Drilling And Construction Costs [Member]
Balance	761,129	611,553	379,117
Cost incurred during the year	473,422	489,953	403,296
Transfer of projects under exploration and development to projects under construction			3,494
Write off of unsuccessful exploration costs	(993)
Balance	618,416	761,129	611,553
Transfer of completed projects to property, plant and equipment	(615,142)	(340,377)	(174,354)
Construction in Progress [Member] | Interest Capitalized [Member]
Balance	25,645	20,072	9,526
Cost incurred during the year	15,181	5,573	10,546
Transfer of projects under exploration and development to projects under construction			0
Write off of unsuccessful exploration costs	0
Balance	22,919	25,645	20,072
Transfer of completed projects to property, plant and equipment	$ (17,907)	$ 0	$ 0