Debt (Schedule of Long-term Debt) (Details) - USD ($)	Dec. 31, 2017	Nov. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt	$ 875,968,000		$ 302,200,000
Long term debt, carrying amount	904,950,000
Less: Unamortized Debt Issuance Costs	21,129,000		4,343,000
Less amounts due in one year	19,318,000		373,000
Long-Term Debt	856,650,000		301,827,000
Current portion of capital lease obligations	3,164,000		3,703,000
Loans Payable \| Term Loan B
Debt Instrument [Line Items]
Long-term debt	392,147,000		0
Less: Unamortized Debt Issuance Costs	7,853,000
Principal	$ 400,000,000
Weighted average interest rate (as a percent)	7.47%
Loans Payable \| MEDCO Revenue Bonds in Series due September 2025 at 5.75%
Debt Instrument [Line Items]
Long term debt, carrying amount	$ 102,865,000		102,865,000
Stated interest rate (as a percent)	5.75%
Loans Payable \| Term Loan A
Debt Instrument [Line Items]
Long term debt, carrying amount	$ 100,000,000		0
Principal	$ 100,000,000
Weighted average interest rate (as a percent)	5.92%
Loans Payable \| Advance royalty commitments
Debt Instrument [Line Items]
Long term debt, carrying amount	$ 2,085,000		$ 2,678,000
Weighted average interest rate (as a percent)	9.42%		7.73%
Senior Notes \| Senior Secured Second Lien Notes due 2025
Debt Instrument [Line Items]
Long term debt, carrying amount	$ 300,000,000		$ 0
Principal	$ 300,000,000	$ 300,000,000
Stated interest rate (as a percent)	11.00%	11.00%
Line of Credit \| Revolving Credit Facility - CONSOL Coal Resources LP
Debt Instrument [Line Items]
Long term debt, carrying amount	$ 0		$ 201,000,000

Amount of capital lease obligation due within one year or the normal operating cycle, if longer.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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