v3.26.1
Financial Instruments and Risk Management (Derivative Instrument Not Designated as Cash Flow Hedged Narrative) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
$ / oz
oz
Dec. 31, 2024
USD ($)
Disclosure of detailed information about hedged items [line items]    
Loss on commodity derivatives $ 230.5 $ 24.2
Expense relating to variable lease payments not included in measurement of lease liabilities 118.6 131.9
Settlement of Argonaut legacy gold hedges (Note 13) (113.5) 0.0
Total liabilities 1,938.8 1,751.9
Gold Forward Contracts | Level 2    
Disclosure of detailed information about hedged items [line items]    
Total liabilities 257.0 140.0
Gold Options | Commodity price risk    
Disclosure of detailed information about hedged items [line items]    
Fair value adjustment on contingent consideration $ (117.0) $ (24.2)
Gold Forward Contracts    
Disclosure of detailed information about hedged items [line items]    
Ounces subject to contract, settled | oz 50,000  
Adjustments for gains (losses) on change in fair value of derivatives $ 113.5  
Gold Forward Contracts | 2026    
Disclosure of detailed information about hedged items [line items]    
Ounces subject to contract | oz 50,000  
Gold Forward Contracts | 2027    
Disclosure of detailed information about hedged items [line items]    
Ounces subject to contract | oz 50,000  
Purchase Put Options | Gold Forward Contracts | Commodity price risk    
Disclosure of detailed information about hedged items [line items]    
Average realized price per ounce | $ / oz 1,821