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Contingencies - Schedule of Contingencies Reserve Balance (Details) - New Idria Mercury Mine [Member] - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Loss Contingencies [Line Items]        
Beginning reserve balance $ 11,213 $ 11,241 $ 12,504 $ 12,425
Changes in estimated environmental liability 1,900 900 3,400 900
Payments made (1,080) (718) (3,871) (1,902)
Ending reserve balance [1] 12,033 11,423 12,033 11,423
Beginning receivable balance 7,904 7,050 8,332 8,404
Changes in estimated insurance recovery 1,400 900 2,500 900
Insurance recovery reimbursements (1,071) (483) (2,599) (1,837)
Ending receivable balance [2] $ 8,233 $ 7,467 $ 8,233 $ 7,467
[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..
[2]

(2) As of September 30, 2026, Buckhorn has a total receivable balance related to the probable insurance recovery of $8.2 million, of which $4.9 million is classified in Other accounts receivable and $3.3 million is classified in Other assets (long-term).