WORKERS' COMPENSATION AND PNEUMOCONIOSIS - Roll forward (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Reconciliation of changes in the workers' compensation liability
Beginning balance	$ 47,194	$ 51,108	$ 47,975	$ 49,452	$ 49,452
Changes in accruals	3,658	3,001	10,148	9,071
Payments	(3,784)	(3,503)	(11,278)	(10,008)
Interest accretion	509	551	1,527	1,652
Valuation loss			(795)	990
Ending balance	47,577	$ 51,157	$ 47,577	$ 51,157	$ 47,975
Estimated present value of future obligations and other information
Workers' compensation discount rate			5.18%		4.66%
Other long-term assets
Estimated present value of future obligations and other information
Receivables for traumatic injury claims	$ 4,100		$ 4,100

Represents the change in the liability for workers' compensation due to payments made during the period.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the change in the liability for workers' compensation due to an adjustment for valuation gain or loss.

+ References

No definition available.

+ Details

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- Definition

Represents the change in the liability for workers' compensation due to additional amounts accrued during the period.

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 420
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 4
-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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- References

No definition available.

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- Definition

Carrying amount due after one year of the balance sheet date (or one operating cycle, if longer) of amount due in settlement of a claim for reimbursement from an insurance company when the Company has suffered a loss covered under an insurance policy.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percent discount applied to worker's compensation reserve liability to reduce the reserve to present value.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-6

+ Details

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- Definition

Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
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+ Details

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