(Guarantor Subsidiaries Balance Sheet) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and Cash Equivalents	$ 153,979	$ 13,311	$ 6,639	$ 137
Accounts and Notes Receivable:
Trade	131,545	95,707
Other Receivables	36,552	23,320
Other Receivables - Related Party	0	34
Inventories	53,420	50,161
Prepaid Expenses	23,744	17,601
Total Current Assets	399,240	200,134
Property, Plant and Equipment:
Property, Plant and Equipment	4,676,353	4,593,395
Less Accumulated Depreciation, Depletion and Amortization	2,554,056	2,413,125
Total Property, Plant and Equipment—Net	2,122,297	2,180,270	2,325,181
Other Assets:
Deferred Income Taxes	75,065	184,579
Affiliated Credit Facility	0
Investment in Affiliates	0	0
Other	110,497	122,451
Total Other Assets	185,562	307,030
TOTAL ASSETS	2,707,099	2,687,434	$ 2,867,733
Current Liabilities:
Accounts Payable	109,100	82,897
Accounts Payable (Recoverable)-Related Parties	0	0
Current Portion of Long-Term Debt	22,482	4,076
Other Accrued Liabilities	290,627	292,121
Total Current Liabilities	422,209	379,094
Long-Term Debt		313,639
Total Long-Term Debt	865,289	313,639
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	554,099	659,474
Pneumoconiosis Benefits	149,868	108,073
Asset Retirement Obligations	228,343	246,279
Workers’ Compensation	66,648	65,932
Salary Retirement	52,960	99,872
Other	24,042	14,947
Total Deferred Credits and Other Liabilities	1,075,960	1,194,577
Total CONSOL Energy Inc. Stockholders' Equity	204,260	657,631
Noncontrolling Interest	139,381	142,493
TOTAL LIABILITIES AND EQUITY	2,707,099	2,687,434
Elimination
Current Assets:
Cash and Cash Equivalents	0	0
Accounts and Notes Receivable:
Trade	0	0
Other Receivables	0	0
Other Receivables - Related Party		0
Inventories	0	0
Prepaid Expenses	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	(165,110)
Investment in Affiliates	(645,157)	(654,144)
Other	0	0
Total Other Assets	(810,267)	(654,144)
TOTAL ASSETS	(810,267)	(654,144)
Current Liabilities:
Accounts Payable	18	(1,608)
Accounts Payable (Recoverable)-Related Parties	(163,069)	0
Current Portion of Long-Term Debt	0	0
Other Accrued Liabilities	(4,874)	(59)
Total Current Liabilities	(167,925)	(1,667)
Long-Term Debt		0
Total Long-Term Debt	(165,110)	0
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	(616,613)	(794,970)
Noncontrolling Interest	139,381	142,493
TOTAL LIABILITIES AND EQUITY	(810,267)	(654,144)
Parent Issuer | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	152,235	2
Accounts and Notes Receivable:
Trade	0	0
Other Receivables	17,702	3,654
Other Receivables - Related Party		0
Inventories	0	0
Prepaid Expenses	5,745	2,882
Total Current Assets	175,682	6,538
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	75,065	184,579
Affiliated Credit Facility	165,110
Investment in Affiliates	645,157	654,144
Other	44,177	34,482
Total Other Assets	929,509	873,205
TOTAL ASSETS	1,105,191	879,743
Current Liabilities:
Accounts Payable	20,014	4,411
Accounts Payable (Recoverable)-Related Parties	(2,291)	0
Current Portion of Long-Term Debt	0	3,347
Other Accrued Liabilities	101,994	102,878
Total Current Liabilities	119,717	110,636
Long-Term Debt		11,604
Total Long-Term Debt	728,254	11,604
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	52,960	99,872
Other	0	0
Total Deferred Credits and Other Liabilities	52,960	99,872
Total CONSOL Energy Inc. Stockholders' Equity	204,260	657,631
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,105,191	879,743
Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	105	3,493
Accounts and Notes Receivable:
Trade	0	0
Other Receivables	16,880	19,151
Other Receivables - Related Party		0
Inventories	41,117	38,670
Prepaid Expenses	13,568	11,204
Total Current Assets	71,670	72,518
Property, Plant and Equipment:
Property, Plant and Equipment	3,765,885	3,716,705
Less Accumulated Depreciation, Depletion and Amortization	2,070,646	1,970,947
Total Property, Plant and Equipment—Net	1,695,239	1,745,758
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0
Investment in Affiliates	0	0
Other	50,846	66,906
Total Other Assets	50,846	66,906
TOTAL ASSETS	1,817,755	1,885,182
Current Liabilities:
Accounts Payable	66,271	59,624
Accounts Payable (Recoverable)-Related Parties	36,221	(72,289)
Current Portion of Long-Term Debt	22,405	641
Other Accrued Liabilities	149,425	145,072
Total Current Liabilities	274,322	133,048
Long-Term Debt		104,046
Total Long-Term Debt	135,390	104,046
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	554,099	659,474
Pneumoconiosis Benefits	146,035	106,016
Asset Retirement Obligations	218,728	236,933
Workers’ Compensation	63,244	62,842
Salary Retirement	0	0
Other	23,435	14,484
Total Deferred Credits and Other Liabilities	1,005,541	1,079,749
Total CONSOL Energy Inc. Stockholders' Equity	402,502	568,339
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	1,817,755	1,885,182
Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	106	31
Accounts and Notes Receivable:
Trade	131,545	95,707
Other Receivables	0	0
Other Receivables - Related Party		34
Inventories	0	0
Prepaid Expenses	3	3
Total Current Assets	131,654	95,775
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
Investment in Affiliates	0	0
Other	0	0
Total Other Assets	0	0
TOTAL ASSETS	131,654	95,775
Current Liabilities:
Accounts Payable	8	7
Accounts Payable (Recoverable)-Related Parties	129,139	95,707
Current Portion of Long-Term Debt	0	0
Other Accrued Liabilities	(20)	0
Total Current Liabilities	129,127	95,714
Long-Term Debt		0
Total Long-Term Debt	1,572	0
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	955	61
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	131,654	95,775
CONSOL Coal Resources LP | Non-Guarantor | Reportable Legal Entities
Current Assets:
Cash and Cash Equivalents	1,533	9,785
Accounts and Notes Receivable:
Trade	0	0
Other Receivables	1,970	515
Other Receivables - Related Party		0
Inventories	12,303	11,491
Prepaid Expenses	4,428	3,512
Total Current Assets	20,234	25,303
Property, Plant and Equipment:
Property, Plant and Equipment	910,468	876,690
Less Accumulated Depreciation, Depletion and Amortization	483,410	442,178
Total Property, Plant and Equipment—Net	427,058	434,512
Other Assets:
Deferred Income Taxes	0	0
Affiliated Credit Facility	0
Investment in Affiliates	0	0
Other	15,474	21,063
Total Other Assets	15,474	21,063
TOTAL ASSETS	462,766	480,878
Current Liabilities:
Accounts Payable	22,789	20,463
Accounts Payable (Recoverable)-Related Parties	0	(23,418)
Current Portion of Long-Term Debt	77	88
Other Accrued Liabilities	44,102	44,230
Total Current Liabilities	66,968	41,363
Long-Term Debt		197,989
Total Long-Term Debt	165,183	197,989
Deferred Credits and Other Liabilities:
Postretirement Benefits Other Than Pensions	0	0
Pneumoconiosis Benefits	3,833	2,057
Asset Retirement Obligations	9,615	9,346
Workers’ Compensation	3,404	3,090
Salary Retirement	0	0
Other	607	463
Total Deferred Credits and Other Liabilities	17,459	14,956
Total CONSOL Energy Inc. Stockholders' Equity	213,156	226,570
Noncontrolling Interest	0	0
TOTAL LIABILITIES AND EQUITY	$ 462,766	$ 480,878