Note 9 - Property, Plant and Equipment and Construction-in-process - Construction-in-process (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Construction in progress	$ 893,198	$ 721,483
Projects Under Exploration and Development [Member]
Construction in progress	95,268	50,702	$ 51,528	$ 84,637
Projects Under Exploration and Development [Member] | Up-front Bonus Lease Costs [Member]
Construction in progress	5,335	5,335	5,347	17,018
Projects Under Exploration and Development [Member] | Exploration and Development Costs [Member]
Construction in progress	89,230	44,664	45,478	66,916
Projects Under Exploration and Development [Member] | Interest Capitalized [Member]
Construction in progress	703	703	$ 703	$ 703
Projects Under Construction [Member]
Construction in progress	797,930	670,781
Projects Under Construction [Member] | Up-front Bonus Lease Costs [Member]
Construction in progress	11,156	39,156
Projects Under Construction [Member] | Interest Capitalized [Member]
Construction in progress	25,645	20,072
Projects Under Construction [Member] | Drilling And Construction Costs [Member]
Construction in progress	$ 761,129	$ 611,553