v3.26.3
Contingencies - Schedule of Contingencies Reserve Balance (Parenthetical) (Details) - New Idria Mercury Mine [Member] - USD ($)
$ in Thousands
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
 [1]
Jun. 30, 2025
Dec. 31, 2024
Loss Contingencies [Line Items]            
Accrual for Environmental Loss Contingencies $ 12,033 [1] $ 11,213 $ 12,504 $ 11,423 $ 11,241 $ 12,425
Estimated Insurance Recoveries 8,200          
Location, Statement of Financial Position, Balance [Axis]: us-gaap:AccountsAndOtherReceivablesNetCurrent            
Loss Contingencies [Line Items]            
Estimated Insurance Recoveries 4,900          
Location, Statement of Financial Position, Balance [Axis]: us-gaap:AccountsPayableCurrent            
Loss Contingencies [Line Items]            
Accrual for Environmental Loss Contingencies 200          
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAccruedLiabilitiesCurrent            
Loss Contingencies [Line Items]            
Accrual for Environmental Loss Contingencies $ 8,800          
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration] Other Accrued Liabilities, Current          
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssetsNoncurrent            
Loss Contingencies [Line Items]            
Estimated Insurance Recoveries $ 3,300          
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherLiabilitiesNoncurrent            
Loss Contingencies [Line Items]            
Accrual for Environmental Loss Contingencies $ 3,000          
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration] Other Liabilities, Noncurrent          
[1]

(1) As of September 30, 2026, Buckhorn has a total ending reserve balance of $12.0 million related to the New Idria Mine, of which $8.8 million is classified in Other current liabilities, $3.0 million in Other liabilities (long-term) and $0.2 million in Accounts payable..