v3.26.1
Financial instruments (Schedule of significant unobservable inputs used in fair value measurement of assets and liabilities) (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of fair value measurement of assets [line items]    
Deferred Copper Mountain acquisition consideration $ 14.4 $ 0.0
Wheaton refund liability 7.9 7.3
Fair value [Member]    
Disclosure of fair value measurement of assets [line items]    
Provisionally priced receivables 302.2 171.3
Non-hedge derivatives 0.6 14.3
Investments 130.9 12.1
Financial assets measured at fair value 433.7 197.7
Non-hedge derivatives 31.9 0.3
Deferred Copper Mountain acquisition consideration 17.5 0.0
Contingent Copper Mountain acquisition consideration 14.1 0.0
Agreements with communities 107.2 70.4
Wheaton refund liability 13.9 9.9
Senior unsecured notes 1,022.7 1,111.6
Financial liabilities measured at fair value 1,207.3 1,192.2
Level 1 [Member]    
Disclosure of fair value measurement of assets [line items]    
Provisionally priced receivables 0.0 0.0
Non-hedge derivatives 0.0 0.0
Investments 127.9 10.6
Financial assets measured at fair value 127.9 10.6
Non-hedge derivatives 0.0 0.0
Deferred Copper Mountain acquisition consideration 0.0  
Contingent Copper Mountain acquisition consideration 0.0  
Agreements with communities 0.0 0.0
Wheaton refund liability 0.0 0.0
Senior unsecured notes 1,022.7 1,111.6
Financial liabilities measured at fair value 1,022.7 1,111.6
Level 2 [Member]    
Disclosure of fair value measurement of assets [line items]    
Provisionally priced receivables 302.2 171.3
Non-hedge derivatives 0.6 14.3
Investments 0.0 0.0
Financial assets measured at fair value 302.8 185.6
Non-hedge derivatives 31.9 0.3
Deferred Copper Mountain acquisition consideration 0.0  
Contingent Copper Mountain acquisition consideration 0.0  
Agreements with communities 0.0 0.0
Wheaton refund liability 0.0 0.0
Senior unsecured notes 0.0 0.0
Financial liabilities measured at fair value 31.9 0.3
Level 3 [Member]    
Disclosure of fair value measurement of assets [line items]    
Provisionally priced receivables 0.0 0.0
Non-hedge derivatives 0.0 0.0
Investments 3.0 1.5
Financial assets measured at fair value 3.0 1.5
Non-hedge derivatives 0.0 0.0
Deferred Copper Mountain acquisition consideration 17.5  
Contingent Copper Mountain acquisition consideration 14.1  
Agreements with communities 107.2 70.4
Wheaton refund liability 13.9 9.9
Senior unsecured notes 0.0 0.0
Financial liabilities measured at fair value $ 152.7 $ 80.3