Investment in Affiliates - Schedule of Combined Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net income (loss)	$ 9,884	$ 9,156	$ 2,532	$ 3,288	$ (3,593)	$ 835	$ 21,572	$ 530
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Other							94	837
Changes in operating assets and liabilities:
Other current assets							21,454	936
Accounts payable and other accrued liabilities							(23,007)	5
Net cash provided by operating activities							61,171	25,465
Cash flows from investing activities:
Net cash used by investing activities							0	0
Cash flows from financing activities:
Net cash provided (used) by financing activities							77	(9,000)
Cash and cash equivalents, beginning of period			55,484			17,004	55,484	17,004
Cash and cash equivalents, end of period	116,732			33,469			116,732	33,469
Supplemental Cash Flow Information
Interest paid							16	417
Interest earned							3,206	690
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Cash flows from operating activities:
Net income (loss)	25,720			15,053			56,379	28,500
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Depreciation, depletion and amortization	17,824			16,712			58,901	59,558
Accretion							652	866
Deferred taxes							10,210	4,743
Unrealized loss (gain) on foreign currency rate change							105	(5,007)
Other							0	(6)
Changes in operating assets and liabilities:
VAT receivable							(1,326)	11,215
Receivables							(1,012)	16,725
Inventories							(1,379)	(1,429)
Other current assets							(2,190)	403
Income tax receivable							8,495	(633)
Accounts payable and other accrued liabilities							21,438	(8,596)
Payables to related parties							(290)	(730)
Asset Retirement Obligation							0	(1,820)
Net cash provided by operating activities							149,983	103,789
Cash flows from investing activities:
Mine development							(32,263)	(27,151)
Purchase of property, plant and equipment							(8,885)	(13,506)
Materials and supplies inventory							0	(503)
Net cash used by investing activities							(41,148)	(41,160)
Cash flows from financing activities:
Equipment loan and lease payments							(47)	(532)
Capital distributions							(95,000)	(50,000)
Dividends paid to partners							(14,207)	0
Net cash provided (used) by financing activities							(109,254)	(50,532)
Net increase in cash and cash equivalents							(419)	12,097
Cash and cash equivalents, beginning of period			$ 34,303			$ 34,936	34,303	34,936
Cash and cash equivalents, end of period	$ 33,884			$ 47,033			33,884	47,033
Supplemental Cash Flow Information
Interest paid							851	484
Interest earned							$ 892	$ 1,147