v3.26.1
Exploration and Evaluation Expenditures - Summary of Company's Exploration and Evaluation Expenditures (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Thacker Pass and Other Project Expenditures      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures $ 6,689 $ 10,078 $ 21,214
Thacker Pass and Other Project Expenditures | Geological, Consulting and Salaries      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 3,796 6,013 9,239
Thacker Pass and Other Project Expenditures | Permitting and Environmental      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 98 222  
Thacker Pass and Other Project Expenditures | Field Supplies and Other      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 1,761 2,289 5,996
Thacker Pass and Other Project Expenditures | Depreciation      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 140 207 468
Thacker Pass and Other Project Expenditures | Drilling and Geological Expenses      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 894 1,347 5,511
Millennial Projects      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 5,200 8,437 18,051
Millennial Projects | Geological, Consulting and Salaries      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 2,307 4,372 6,086
Millennial Projects | Permitting and Environmental      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 98 222  
Millennial Projects | Field Supplies and Other      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 1,761 2,289 5,986
Millennial Projects | Depreciation      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 140 207 468
Millennial Projects | Drilling and Geological Expenses      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 894 1,347 5,511
Other Project      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures 1,489 1,641 3,163
Other Project | Geological, Consulting and Salaries      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures $ 1,489 $ 1,641 3,153
Other Project | Field Supplies and Other      
Disclosure Of Exploration Expenditures [Line Items]      
Total exploration expenditures     $ 10