Debt (Details Textual) - USD ($) shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended			9 Months Ended
	Feb. 21, 2024	Mar. 31, 2021	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	May 02, 2022
Debt Instrument [Line Items]
Gain on debt extinguishment			$ 0		$ 774	$ 417	$ 3,735
Finance Lease Obligations						32,400
Senior Notes due 2029
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 375,000
Proceeds from debt		$ 367,500
Extinguishment of debt				$ 5,900
Converted shares (in shares)				1,800
Gain on debt extinguishment				$ 400
Revolving Credit Facility
Debt Instrument [Line Items]
Additional increases in RCF	$ 100,000
Non-capitalized underground mine development costs	15,000
Line of credit facility	10,000
Letters of credit outstanding, amount			$ 29,600			$ 29,600
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Stated interest rate			7.50%			7.50%
Long-term debt			$ 225,000			$ 225,000
Amount available subject to debt covenants			$ 145,400			$ 145,400
Revolving Credit Facility | Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000							$ 390,000