Supplemental Quarterly Information (unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
	Nov. 28, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue and Other Income:
Coal Revenue		$ 288,254	$ 279,245	$ 303,707	$ 316,448	$ 321,171	$ 267,685	$ 250,562	$ 226,164	$ 1,187,654	$ 1,065,582	$ 1,289,036
Terminal Revenue		17,260	15,065	14,855	12,886	11,148	4,549	8,058	7,709
Freight Revenue		21,845	21,803	17,762	12,282	12,519	9,392	11,447	13,110	73,692	46,468	20,499
Miscellaneous Other Income		20,771	19,713	10,145	22,650	32,418	13,569	20,627	15,506	73,279	82,120	68,193
Gain (Loss) on Sale of Assets		4,188	(513)	5,582	7,955	1,129	194	3,933	(28)	17,212	5,228	13,025
Total Revenue and Other Income		352,318	335,313	352,051	372,221	378,385	295,389	294,627	262,461	1,411,903	1,230,862	1,421,720
Costs and Expenses:
Operating and Other Costs		204,306	229,527	222,882	229,994	253,907	215,824	226,257	181,189	886,709	877,177	699,594
Depreciation, Depletion and Amortization		47,088	46,653	25,268	52,993	50,296	49,850	29,314	48,662	172,002	178,122	195,337
Freight Expense		21,845	21,803	17,762	12,282	12,519	9,392	11,447	13,110	73,692	46,468	20,499
Selling, General and Administrative Costs		25,008	21,180	20,338	17,079	19,850	12,157	10,460	7,560	83,605	50,027	55,720
Interest Expense		14,270	3,862	3,944	4,022	4,075	3,481	3,357	3,140	26,098	14,053	7,544
Total Costs and Expenses		312,517	323,025	290,194	316,370	340,647	290,704	280,835	253,661	1,242,106	1,165,847	978,694
Earnings Before Income Tax		39,801	12,288	61,857	55,851	37,738	4,685	13,792	8,800	169,797	65,015	443,026
Income Tax Expense		64,441	3,770	9,611	9,406	14,824	(66)	(109)	(84)	87,228	14,565	125,605
Net Income (Loss)		(24,640)	8,518	52,246	46,445	22,914	4,751	13,901	8,884	82,569	50,450	317,421
Less: Net Income Attributable to Noncontrolling Interest		4,373	790	4,313	5,464	4,413	2,248	1,179	1,114	14,940	8,954	10,410
Net Income (Loss) Attributable to CONSOL Energy Shareholders		$ (29,013)	$ 7,728	$ 47,933	$ 40,981	$ 18,501	$ 2,503	$ 12,722	$ 7,770	$ 67,629	$ 41,496	$ 307,011
Earnings Per Share:
Basic (in dollars per share)		$ (1.04)	$ 0.28	$ 1.71	$ 1.47	$ 0.66	$ 0.09	$ 0.45	$ 0.28	$ 2.42	$ 1.48	$ 10.98
Diluted (in dollars per share)		$ (1.04)	$ 0.00	$ 0.00	$ 0.00	$ 0.66	$ 0.00	$ 0.00	$ 0.00	$ 2.40	$ 1.48	$ 10.98
Common stock distributed (in shares)	27,968									27,968	0	0