GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION - Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Current Assets:
Cash and Cash Equivalents	$ 250,452	$ 153,979
Trade	78,649	131,545
Other Receivables	29,208	36,552
Inventories	52,470	53,420
Prepaid Expenses and Other Assets	58,123	23,744
Total Current Assets	468,902	399,240
Property, Plant and Equipment:
Property, Plant and Equipment	4,796,141	4,676,353
Less—Accumulated Depreciation, Depletion and Amortization	2,692,450	2,554,056
Total Property, Plant and Equipment—Net	2,103,691	2,122,297
Other Assets:
Deferred Income Taxes	72,120	75,065
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	101,215	110,497
Total Other Assets	173,335	185,562
TOTAL ASSETS	2,745,928	2,707,099	$ 2,588,529
Current Liabilities:
Accounts Payable	102,401	109,100
Accounts Payable (Recoverable)-Related Parties	0	0
Current Portion of Long-Term Debt	20,945	22,482
Other Accrued Liabilities	249,758	290,627
Total Current Liabilities	373,104	422,209
Long-Term Debt	857,011	865,289
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	541,373	554,099
Pneumoconiosis Benefits	151,676	149,868
Asset Retirement Obligations	236,191	228,343
Workers’ Compensation	65,346	66,648
Salary Retirement	39,921	52,960
Other	18,845	24,042
Total Deferred Credits and Other Liabilities	1,053,352	1,075,960
Total CONSOL Energy Inc. Stockholders' Equity	320,934	204,260
Noncontrolling Interest	141,527	139,381
TOTAL LIABILITIES AND EQUITY	2,745,928	2,707,099
Elimination
Current Assets:
Cash and Cash Equivalents	0	0
Trade	0	0
Other Receivables	0	0
Inventories	0	0
Prepaid Expenses and Other Assets	0	0
Total Current Assets	0	0
Property, Plant and Equipment:
Property, Plant and Equipment	0	0
Less—Accumulated Depreciation, Depletion and Amortization	0	0
Total Property, Plant and Equipment—Net	0	0
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	(147,277)	(165,110)
Investment in Affiliates	(640,187)	(645,157)
Other	0	0
Total Other Assets	(787,464)	(810,267)
TOTAL ASSETS	(787,464)	(810,267)
Current Liabilities:
Accounts Payable	1,867	18
Accounts Payable (Recoverable)-Related Parties	(123,015)	(163,069)
Current Portion of Long-Term Debt	0	0
Other Accrued Liabilities	(1,867)	(4,874)
Total Current Liabilities	(123,015)	(167,925)
Long-Term Debt	(147,277)	(165,110)
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	0	0
Asset Retirement Obligations	0	0
Workers’ Compensation	0	0
Salary Retirement	0	0
Other	0	0
Total Deferred Credits and Other Liabilities	0	0
Total CONSOL Energy Inc. Stockholders' Equity	(658,699)	(616,613)
Noncontrolling Interest	141,527	139,381
TOTAL LIABILITIES AND EQUITY	(787,464)	(810,267)
CCR Non-Guarantor
Current Liabilities:
Accounts Payable (Recoverable)-Related Parties	1,573	3,071
Parent Issuer | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	249,287	152,235
Trade	0	0
Other Receivables	16,917	17,702
Inventories	0	0
Prepaid Expenses and Other Assets	7,840	5,745
Total Current Assets	274,044	175,682
Property, Plant and Equipment:
Property, Plant and Equipment	0	0
Less—Accumulated Depreciation, Depletion and Amortization	0	0
Total Property, Plant and Equipment—Net	0	0
Other Assets:
Deferred Income Taxes	72,120	75,065
Affiliated Credit Facility	147,277	165,110
Investment in Affiliates	640,187	645,157
Other	39,011	44,177
Total Other Assets	898,595	929,509
TOTAL ASSETS	1,172,639	1,105,191
Current Liabilities:
Accounts Payable	8,709	20,014
Accounts Payable (Recoverable)-Related Parties	(2,291)	(2,291)
Current Portion of Long-Term Debt	6,796	0
Other Accrued Liabilities	101,272	101,994
Total Current Liabilities	114,486	119,717
Long-Term Debt	697,298	728,254
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	0	0
Asset Retirement Obligations	0	0
Workers’ Compensation	0	0
Salary Retirement	39,921	52,960
Other	0	0
Total Deferred Credits and Other Liabilities	39,921	52,960
Total CONSOL Energy Inc. Stockholders' Equity	320,934	204,260
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,172,639	1,105,191
Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	245	105
Trade	0	0
Other Receivables	11,964	16,880
Inventories	40,445	41,117
Prepaid Expenses and Other Assets	18,285	13,568
Total Current Assets	70,939	71,670
Property, Plant and Equipment:
Property, Plant and Equipment	3,860,242	3,765,885
Less—Accumulated Depreciation, Depletion and Amortization	2,176,357	2,070,646
Total Property, Plant and Equipment—Net	1,683,885	1,695,239
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	47,261	50,846
Total Other Assets	47,261	50,846
TOTAL ASSETS	1,802,085	1,817,755
Current Liabilities:
Accounts Payable	71,169	66,271
Accounts Payable (Recoverable)-Related Parties	36,220	36,221
Current Portion of Long-Term Debt	10,696	22,405
Other Accrued Liabilities	114,392	149,425
Total Current Liabilities	232,477	274,322
Long-Term Debt	153,708	135,390
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	541,373	554,099
Pneumoconiosis Benefits	146,729	146,035
Asset Retirement Obligations	226,586	218,728
Workers’ Compensation	61,816	63,244
Salary Retirement	0	0
Other	18,240	23,435
Total Deferred Credits and Other Liabilities	994,744	1,005,541
Total CONSOL Energy Inc. Stockholders' Equity	421,156	402,502
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,802,085	1,817,755
Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	0	106
Trade	78,649	131,545
Other Receivables	0	0
Inventories	0	0
Prepaid Expenses and Other Assets	25,862	3
Total Current Assets	104,511	131,654
Property, Plant and Equipment:
Property, Plant and Equipment	0	0
Less—Accumulated Depreciation, Depletion and Amortization	0	0
Total Property, Plant and Equipment—Net	0	0
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	0	0
Total Other Assets	0	0
TOTAL ASSETS	104,511	131,654
Current Liabilities:
Accounts Payable	0	8
Accounts Payable (Recoverable)-Related Parties	87,513	129,139
Current Portion of Long-Term Debt	0	0
Other Accrued Liabilities	0	(20)
Total Current Liabilities	87,513	129,127
Long-Term Debt	0	1,572
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	0	0
Asset Retirement Obligations	0	0
Workers’ Compensation	0	0
Salary Retirement	0	0
Other	0	0
Total Deferred Credits and Other Liabilities	0	0
Total CONSOL Energy Inc. Stockholders' Equity	16,998	955
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	104,511	131,654
Non-Guarantor | CCR Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	920	1,533
Trade	0	0
Other Receivables	327	1,970
Inventories	12,025	12,303
Prepaid Expenses and Other Assets	6,136	4,428
Total Current Assets	19,408	20,234
Property, Plant and Equipment:
Property, Plant and Equipment	935,899	910,468
Less—Accumulated Depreciation, Depletion and Amortization	516,093	483,410
Total Property, Plant and Equipment—Net	419,806	427,058
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	14,943	15,474
Total Other Assets	14,943	15,474
TOTAL ASSETS	454,157	462,766
Current Liabilities:
Accounts Payable	20,656	22,789
Accounts Payable (Recoverable)-Related Parties	1,573	0
Current Portion of Long-Term Debt	3,453	77
Other Accrued Liabilities	35,961	44,102
Total Current Liabilities	61,643	66,968
Long-Term Debt	153,282	165,183
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	4,947	3,833
Asset Retirement Obligations	9,605	9,615
Workers’ Compensation	3,530	3,404
Salary Retirement	0	0
Other	605	607
Total Deferred Credits and Other Liabilities	18,687	17,459
Total CONSOL Energy Inc. Stockholders' Equity	220,545	213,156
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	$ 454,157	$ 462,766