Represents additional authorized amount of stock and debt repurchase program.

No definition available.

Name:	ceix_StockAndDebtRepurchaseProgramAdditionalAuthorizedAmount
Namespace Prefix:	ceix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents authorized amount of stock and debt repurchase program.

+ References

No definition available.

+ Details

Name:	ceix_StockAndDebtRepurchaseProgramAuthorizedAmount
Namespace Prefix:	ceix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents remaining authorized amount of stock and debt repurchase program.

+ References

No definition available.

+ Details

Name:	ceix_StockAndDebtRepurchaseProgramRemainingAuthorizedAmount
Namespace Prefix:	ceix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ceix_TaxexemptSolidWasteDisposalRevenueBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 19 - Subsequent Events (Details Textual) - Subsequent Event [Member] - USD ($) $ in Millions	Apr. 13, 2021	May 04, 2021	Apr. 28, 2021
Stock and Debt Repurchase Program, Additional Authorized Amount			$ 50
Stock and Debt Repurchase Program, Authorized Amount			$ 320
Stock and Debt Repurchase Program, Remaining Authorized Amount		$ 132
Tax-exempt Solid Waste Disposal Revenue Bonds [Member]
Debt Instrument, Face Amount	$ 75
Debt Instrument, Term (Year)	30 years
Debt Instrument, Interest Rate, Effective Percentage	9.00%