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Decommissioning Liabilities (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Asset Retirement Obligation Disclosure [Line Items]    
Estimated reclamation discount rate 2.90% 1.80%
Closure cost obligations discount rate 10.50% 10.50%
Decommissioning liability $ 134.0 $ 114.9
Bottom of range    
Asset Retirement Obligation Disclosure [Line Items]    
Inflation rate 1.90% 1.90%
Top of range    
Asset Retirement Obligation Disclosure [Line Items]    
Inflation rate 9.50% 9.50%