Contingencies - Schedule of Contingencies Reserve Balance (Parenthetical) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023		Sep. 30, 2024		Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
EPA Notice Letter [Member]
Loss Contingencies [Line Items]
Payment made to settle past cost claims	$ 1,900
New Idria Mercury Mine [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 11,200	[1]	$ 11,784	[1]	$ 12,492	$ 13,182	$ 12,082	$ 11,855
Estimated Insurance Recoveries			7,200
New Idria Mercury Mine [Member] | Other Current Liabilities [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies			$ 7,100
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]			Other Accrued Liabilities, Current
New Idria Mercury Mine [Member] | Other Noncurrent Liabilities [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies			$ 4,700
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]			Other Liabilities, Noncurrent
New Idria Mercury Mine [Member] | Accounts Receivable [Member]
Loss Contingencies [Line Items]
Estimated Insurance Recoveries			$ 3,000
New Idria Mercury Mine [Member] | Other Noncurrent Assets [Member]
Loss Contingencies [Line Items]
Estimated Insurance Recoveries			$ 4,200

[1] (1) As of September 30, 2024, Buckhorn has a total ending reserve balance of $11.8 million related to the New Idria Mine, of which $7.1 million is classified in Other current liabilities and $4.7 million in Other liabilities (long-term).