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Exploration and Evaluation Assets - Schedule of Exploration and Evaluation Assets Relating to Thacker Pass Project (Details) - Exploration and Evaluation Assets - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Acquisition costs    
Total exploration and evaluation assets, beginning balance $ 343,092 $ 348,645
Transfers to PP&E   (9,514)
Acquisition of Arena Minerals   1,385
Additions 702 3,416
Write offs   (70)
Assets distributed to the shareholders   (770)
Total exploration and evaluation assets, ending balance 343,794 343,092
Thacker Pass    
Acquisition costs    
Total exploration and evaluation assets, beginning balance 0 9,514
Transfers to PP&E   (9,514)
Acquisition of Arena Minerals   0
Additions 0 0
Write offs   0
Assets distributed to the shareholders   0
Total exploration and evaluation assets, ending balance 0 0
Millennial Projects    
Acquisition costs    
Total exploration and evaluation assets, beginning balance 341,707 339,131
Transfers to PP&E   0
Acquisition of Arena Minerals   0
Additions 702 2,646
Write offs   (70)
Assets distributed to the shareholders   0
Total exploration and evaluation assets, ending balance 342,409 341,707
Other Claims    
Acquisition costs    
Total exploration and evaluation assets, beginning balance 1,385 0
Transfers to PP&E   0
Acquisition of Arena Minerals   1,385
Additions 0 770
Write offs   0
Assets distributed to the shareholders   (770)
Total exploration and evaluation assets, ending balance $ 1,385 $ 1,385