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Background and basis of preparation (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Investments subject to significant influence      
Proceeds from sale of a subsidiary $ 0 $ 9,696  
Revision of Prior Period, Error Correction, Adjustment      
Investments subject to significant influence      
Proceeds from sale of a subsidiary   $ 9,700  
Subsidiaries | VRB Energy Inc      
Investments subject to significant influence      
Subsidiary, ownership percentage, parent 90.00%   90.00%
Subsidiaries | Computational Geosciences Inc      
Investments subject to significant influence      
Subsidiary, ownership percentage, parent 94.30%   94.30%
Subsidiaries | Cordoba Minerals Corp      
Investments subject to significant influence      
Subsidiary, ownership percentage, parent 59.30%   60.80%
Maaden Joint Venture      
Investments subject to significant influence      
Ownership percentage 50.00%    
VRB China | VRB Energy Inc      
Investments subject to significant influence      
Ownership percentage 49.00%