Supplemental Quarterly Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue and Other Income:
Revenue from Contract with Customers									$ 1,375,559	$ 1,472,790	$ 1,321,412
Miscellaneous Other Income	$ 16,675	$ 11,188	$ 12,194	$ 13,292	$ 11,426	$ 10,978	$ 10,369	$ 25,887	53,349	58,660	73,279
Gain on Sale of Assets	9	714	933	339	292	(85)	104	254	1,995	565	17,212
Total Revenue and Other Income	342,635	333,346	384,309	370,613	382,236	324,248	415,273	410,258	1,430,903	1,532,015	1,411,903
Costs and Expenses:
Operating and Other Costs	229,603	234,849	253,448	230,112	245,672	222,781	248,195	229,802	948,012	946,450	886,709
Depreciation, Depletion and Amortization	55,852	54,370	46,151	50,724	45,590	51,242	54,961	49,471	207,097	201,264	172,002
Freight Expense	5,552	3,599	3,854	6,662	5,798	2,443	17,444	17,887	19,667	43,572	73,692
Selling, General and Administrative Costs	14,210	14,690	16,288	21,923	17,631	18,526	15,705	13,484	67,111	65,346	83,605
Loss (Gain) on Debt Extinguishment	(989)	801	1,500	23,143	773	0	1,723	1,426	24,455	3,922	0
Interest Expense, net	16,224	15,598	16,046	18,596	20,437	20,862	21,504	21,045	66,464	83,848	26,098
Total Costs and Expenses	320,452	323,907	337,287	351,160	335,901	315,854	359,532	333,115	1,332,806	1,344,402	1,242,106
Earnings Before Income Tax	22,183	9,439	47,022	19,453	46,335	8,394	55,741	77,143	98,097	187,613	169,797
Income Tax (Benefit) Expense	4,782	2,415	(1,808)	(850)	301	(690)	3,032	6,185	4,539	8,828	87,228
Net Income	17,401	7,024	48,830	20,303	46,034	9,084	52,709	70,958	93,558	178,785	82,569
Less: Net Income Attributable to Noncontrolling Interest	3,455	2,684	5,550	5,868	6,362	3,350	7,547	8,550	17,557	25,809	14,940
Net Income Attributable to CONSOL Energy Inc. Shareholders	$ 13,946	$ 4,340	$ 43,280	$ 14,435	$ 39,672	$ 5,734	$ 45,162	$ 62,408	$ 76,001	$ 152,976	$ 67,629
Earnings per Share:
Basic (in dollars per share)	$ 0.54	$ 0.16	$ 1.57	$ 0.52	$ 1.43	$ 0.20	$ 1.61	$ 2.23	$ 2.82	$ 5.48	$ 2.42
Diluted (in dollars per share)	$ 0.54	$ 0.16	$ 1.56	$ 0.52	$ 1.41	$ 0.20	$ 1.58	$ 2.20	$ 2.81	$ 5.38	$ 2.40
Coal Revenue
Revenue and Other Income:
Revenue from Contract with Customers	$ 303,865	$ 301,542	$ 350,620	$ 332,502	$ 347,789	$ 294,797	$ 370,697	$ 351,009	$ 1,288,529	$ 1,364,292	$ 1,187,654
Terminal Revenue
Revenue and Other Income:
Revenue from Contract with Customers	16,534	16,303	16,708	17,818	16,931	16,115	16,659	15,221	67,363	64,926	60,066
Freight Revenue
Revenue and Other Income:
Revenue from Contract with Customers	$ 5,552	$ 3,599	$ 3,854	$ 6,662	$ 5,798	$ 2,443	$ 17,444	$ 17,887	$ 19,667	$ 43,572	$ 73,692