v3.26.1
Financial instruments - (Schedule of liquidity risk) (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of detailed information about financial instruments [line items]      
Cash $ 568.9 $ 541.8 $ 249.8
Short-term investments 0.0 40.0  
Deferred Copper Mountain acquisition consideration (14.4) 0.0  
Wheaton refund liability (7.9) (7.3)  
Carrying amount [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 568.9 541.8  
Short-term investments   40.0  
Collateral deposits   0.6  
Restricted cash 0.2 0.4  
Trade and other receivables 347.6 185.5  
Non-hedge derivative assets 0.6 14.3  
Assets used to manage liquidity risk 917.3 782.6  
Trade and other payables (330.5) (255.2)  
Deferred Copper Mountain acquisition consideration (17.4)    
Contingent Copper Mountain acquisition consideration (13.9)    
Agreements with communities (105.9) (68.4)  
Senior unsecured notes (1,010.9) (1,111.1)  
Wheaton refund liability (7.9) (7.3)  
Non-derivative financial liabilities (1,486.5) (1,442.0)  
Non-hedge derivative contracts (31.9) (0.3)  
Derivative financial liabilities (31.9) (0.3)  
Contractual cash flows [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 568.9 541.8  
Short-term investments   40.0  
Collateral deposits   0.6  
Restricted cash 0.2 0.4  
Trade and other receivables 347.6 185.5  
Non-hedge derivative assets 0.6 14.3  
Assets used to manage liquidity risk 917.3 782.6  
Trade and other payables (330.5) (255.2)  
Deferred Copper Mountain acquisition consideration (21.0)    
Contingent Copper Mountain acquisition consideration (18.8)    
Agreements with communities (136.7) (99.0)  
Senior unsecured notes (1,141.8) (1,305.7)  
Wheaton refund liability (79.2) (79.2)  
Non-derivative financial liabilities (1,728.0) (1,739.1)  
Non-hedge derivative contracts (31.9) (0.3)  
Derivative financial liabilities (31.9) (0.3)  
Less than 1 Year [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 568.9 541.8  
Short-term investments   40.0  
Collateral deposits   0.6  
Restricted cash 0.2 0.4  
Trade and other receivables 347.6 185.5  
Non-hedge derivative assets 0.6 14.3  
Assets used to manage liquidity risk 917.3 782.6  
Trade and other payables (330.5) (255.2)  
Deferred Copper Mountain acquisition consideration (3.0)    
Contingent Copper Mountain acquisition consideration 0.0    
Agreements with communities (67.0) (26.1)  
Senior unsecured notes (516.4) (59.1)  
Wheaton refund liability 0.0 0.0  
Non-derivative financial liabilities (916.9) (340.4)  
Non-hedge derivative contracts (31.9) (0.3)  
Derivative financial liabilities (31.9) (0.3)  
1 - 3 Years [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 0.0 0.0  
Restricted cash 0.0 0.0  
Trade and other receivables 0.0 0.0  
Non-hedge derivative assets 0.0 0.0  
Assets used to manage liquidity risk 0.0 0.0  
Trade and other payables 0.0 0.0  
Deferred Copper Mountain acquisition consideration (6.0)    
Contingent Copper Mountain acquisition consideration 0.0    
Agreements with communities (12.3) (17.0)  
Senior unsecured notes (66.4) (654.4)  
Wheaton refund liability 0.0 0.0  
Non-derivative financial liabilities (84.7) (671.4)  
Non-hedge derivative contracts 0.0 0.0  
Derivative financial liabilities 0.0 0.0  
3 -5 Years [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 0.0 0.0  
Restricted cash 0.0 0.0  
Trade and other receivables 0.0 0.0  
Non-hedge derivative assets 0.0 0.0  
Assets used to manage liquidity risk 0.0 0.0  
Trade and other payables 0.0 0.0  
Deferred Copper Mountain acquisition consideration (6.0)    
Contingent Copper Mountain acquisition consideration (7.5)    
Agreements with communities (9.2) (8.3)  
Senior unsecured notes (559.0) (592.2)  
Wheaton refund liability 0.0 0.0  
Non-derivative financial liabilities (581.7) (600.5)  
Non-hedge derivative contracts 0.0 0.0  
Derivative financial liabilities 0.0 0.0  
More than 5 Years [Member]      
Disclosure of detailed information about financial instruments [line items]      
Cash 0.0 0.0  
Restricted cash 0.0 0.0  
Trade and other receivables 0.0 0.0  
Non-hedge derivative assets 0.0 0.0  
Assets used to manage liquidity risk 0.0 0.0  
Trade and other payables 0.0 0.0  
Deferred Copper Mountain acquisition consideration (6.0)    
Contingent Copper Mountain acquisition consideration (11.3)    
Agreements with communities (48.2) (47.6)  
Senior unsecured notes 0.0 0.0  
Wheaton refund liability (79.2) (79.2)  
Non-derivative financial liabilities (144.7) (126.8)  
Non-hedge derivative contracts 0.0 0.0  
Derivative financial liabilities $ 0.0 $ 0.0