v3.25.4

Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2025	Jan. 30, 2026	Jun. 30, 2025
Cover [Abstract]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Dec. 31, 2025
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38147
Entity Registrant Name	Core Natural Resources, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-1954058
Entity Address, Address Line One	275 Technology Drive
Entity Address, Address Line Two	Suite 101
Entity Address, City or Town	Canonsburg
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15317-9565
City Area Code	724
Local Phone Number	416-8300
Title of 12(b) Security	Common Stock ($0.01 par value)
Trading Symbol	CNR
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 3,514,239,816
Entity Common Stock, Shares Outstanding		50,979,544
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE: Portions of Core Natural Resources, Inc.’s Proxy Statement for the 2026 Annual Meeting of Stockholders to be filed within 120 days of the end of the registrant’s fiscal year are incorporated by reference in Items 10, 11, 12, 13 and 14 of Part III.
Entity Central Index Key	0001710366
Amendment Flag	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2025

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End date of current fiscal year in the format --MM-DD.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Section 310

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Subsection f

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Address Line 2 such as Street or Suite number

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A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

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Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

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Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure.

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Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

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Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.

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Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

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The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter.

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The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

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Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.

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Indicates that the company is a Smaller Reporting Company (SRC).

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The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

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Indicate 'Yes' or 'No' if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.

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Indicate 'Yes' or 'No' if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Is used on Form Type: 10-K, 10-Q, 8-K, 20-F, 6-K, 10-K/A, 10-Q/A, 20-F/A, 6-K/A, N-CSR, N-Q, N-1A.

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Local phone number for entity.

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Title of a 12(b) registered security.

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Trading symbol of an instrument as listed on an exchange.

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Core Natural Resources, Inc. 10-K/A