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Commitments and Contingencies - Narrative (Details) tonOfCoal in Thousands, $ in Thousands		1 Months Ended	3 Months Ended
	Jan. 14, 2025	Apr. 30, 2024 tonOfCoal	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Jan. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Long-term Purchase Commitment [Line Items]
Arrangement, term		3 years
Black Lung
Long-term Purchase Commitment [Line Items]
Required documents submission period	60 days
Surety Bond
Long-term Purchase Commitment [Line Items]
Outstanding surety bonds			$ 181,079
Reclamation-Related Obligations | Collateral Pledged
Long-term Purchase Commitment [Line Items]
Restricted cash, restricted investments, and deposits			35,002
ABL Facility
Long-term Purchase Commitment [Line Items]
Letters of credit outstanding			42,149			$ 42,149
Minimum
Long-term Purchase Commitment [Line Items]
Number of tons of coal allowed to be loaded | tonOfCoal		1,200
Minimum | Black Lung
Long-term Purchase Commitment [Line Items]
Collateral for black lung obligations					$ 80,000
Maximum
Long-term Purchase Commitment [Line Items]
Number of tons of coal allowed to be loaded | tonOfCoal		2,000
Maximum | Black Lung
Long-term Purchase Commitment [Line Items]
Collateral for black lung obligations					$ 100,000
Additional DTA Investment
Long-term Purchase Commitment [Line Items]
Minimum obligations, year one			27,000
Minimum obligations, year two			27,000
Minimum obligations, year three			27,000
Minimum obligations, year four			27,000
Minimum obligations, year five			27,000
Coal
Long-term Purchase Commitment [Line Items]
Coal royalty expense			$ 24,085	$ 43,828

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477220/954-210-45-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
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-Name Accounting Standards Codification
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