GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION - Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Current Assets:
Cash and Cash Equivalents	$ 278,289	$ 153,979
Trade	87,513	131,545
Other Receivables	31,946	36,552
Inventories	48,345	53,420
Prepaid Expenses and Other Assets	28,199	23,744
Total Current Assets	474,292	399,240
Property, Plant and Equipment:
Property, Plant and Equipment	4,758,267	4,676,353
Less—Accumulated Depreciation, Depletion and Amortization	2,648,812	2,554,056
Total Property, Plant and Equipment—Net	2,109,455	2,122,297
Other Assets:
Deferred Income Taxes	72,490	75,065
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	100,265	110,497
Total Other Assets	172,755	185,562
TOTAL ASSETS	2,756,502	2,707,099	$ 2,626,610
Current Liabilities:
Accounts Payable	103,734	109,100
Accounts Payable (Recoverable)-Related Parties	0	0
Current Portion of Long-Term Debt	20,758	22,482
Other Accrued Liabilities	251,227	290,627
Total Current Liabilities	375,719	422,209
Long-Term Debt	861,329	865,289
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	544,764	554,099
Pneumoconiosis Benefits	151,579	149,868
Asset Retirement Obligations	233,547	228,343
Workers’ Compensation	65,202	66,648
Salary Retirement	44,134	52,960
Other	19,007	24,042
Total Deferred Credits and Other Liabilities	1,058,233	1,075,960
Total CONSOL Energy Inc. Stockholders' Equity	316,949	204,260
Noncontrolling Interest	144,272	139,381
TOTAL LIABILITIES AND EQUITY	2,756,502	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	(137,643)	(165,110)
Investment in Affiliates	(607,354)	(645,157)
Other	0	0
Total Other Assets	(744,997)	(810,267)
TOTAL ASSETS	(744,997)	(810,267)
Current Liabilities:
Accounts Payable	2,025	18
Accounts Payable (Recoverable)-Related Parties	(123,991)	(163,069)
Current Portion of Long-Term Debt	0	0
Other Accrued Liabilities	(2,025)	(4,874)
Total Current Liabilities	(123,991)	(167,925)
Long-Term Debt	(137,643)	(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	(627,635)	(616,613)
Noncontrolling Interest	144,272	139,381
TOTAL LIABILITIES AND EQUITY	(744,997)	(810,267)
CCR Non-Guarantor
Current Liabilities:
Accounts Payable (Recoverable)-Related Parties	3,455	3,071
Parent Issuer | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	277,413	152,235
Trade	0	0
Other Receivables	15,382	17,702
Inventories	0	0
Prepaid Expenses and Other Assets	7,152	5,745
Total Current Assets	299,947	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	72,490	75,065
Affiliated Credit Facility	137,643	165,110
Investment in Affiliates	607,354	645,157
Other	39,677	44,177
Total Other Assets	857,164	929,509
TOTAL ASSETS	1,157,111	1,105,191
Current Liabilities:
Accounts Payable	(3,247)	20,014
Accounts Payable (Recoverable)-Related Parties	(2,291)	(2,291)
Current Portion of Long-Term Debt	6,771	0
Other Accrued Liabilities	96,919	101,994
Total Current Liabilities	98,152	119,717
Long-Term Debt	697,876	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	44,134	52,960
Other	0	0
Total Deferred Credits and Other Liabilities	44,134	52,960
Total CONSOL Energy Inc. Stockholders' Equity	316,949	204,260
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,157,111	1,105,191
Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	230	105
Trade	0	0
Other Receivables	15,050	16,880
Inventories	37,327	41,117
Prepaid Expenses and Other Assets	11,135	13,568
Total Current Assets	63,742	71,670
Property, Plant and Equipment:
Property, Plant and Equipment	3,830,609	3,765,885
Less—Accumulated Depreciation, Depletion and Amortization	2,143,513	2,070,646
Total Property, Plant and Equipment—Net	1,687,096	1,695,239
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	46,081	50,846
Total Other Assets	46,081	50,846
TOTAL ASSETS	1,796,919	1,817,755
Current Liabilities:
Accounts Payable	82,000	66,271
Accounts Payable (Recoverable)-Related Parties	35,314	36,221
Current Portion of Long-Term Debt	10,575	22,405
Other Accrued Liabilities	119,355	149,425
Total Current Liabilities	247,244	274,322
Long-Term Debt	156,492	135,390
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	544,764	554,099
Pneumoconiosis Benefits	146,995	146,035
Asset Retirement Obligations	224,125	218,728
Workers’ Compensation	61,750	63,244
Salary Retirement	0	0
Other	18,402	23,435
Total Deferred Credits and Other Liabilities	996,036	1,005,541
Total CONSOL Energy Inc. Stockholders' Equity	397,147	402,502
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,796,919	1,817,755
Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	0	106
Trade	87,513	131,545
Other Receivables	0	0
Inventories	0	0
Prepaid Expenses and Other Assets	6,214	3
Total Current Assets	93,727	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	93,727	131,654
Current Liabilities:
Accounts Payable	1,486	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	88,999	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	4,728	955
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	93,727	131,654
Non-Guarantor | CCR Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	646	1,533
Trade	0	0
Other Receivables	1,514	1,970
Inventories	11,018	12,303
Prepaid Expenses and Other Assets	3,698	4,428
Total Current Assets	16,876	20,234
Property, Plant and Equipment:
Property, Plant and Equipment	927,658	910,468
Less—Accumulated Depreciation, Depletion and Amortization	505,299	483,410
Total Property, Plant and Equipment—Net	422,359	427,058
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0	0
Investment in Affiliates	0	0
Other	14,507	15,474
Total Other Assets	14,507	15,474
TOTAL ASSETS	453,742	462,766
Current Liabilities:
Accounts Payable	21,470	22,789
Accounts Payable (Recoverable)-Related Parties	3,455	0
Current Portion of Long-Term Debt	3,412	77
Other Accrued Liabilities	36,978	44,102
Total Current Liabilities	65,315	66,968
Long-Term Debt	144,604	165,183
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	4,584	3,833
Asset Retirement Obligations	9,422	9,615
Workers’ Compensation	3,452	3,404
Salary Retirement	0	0
Other	605	607
Total Deferred Credits and Other Liabilities	18,063	17,459
Total CONSOL Energy Inc. Stockholders' Equity	225,760	213,156
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	$ 453,742	$ 462,766