Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings (Deficit)	Parent Net Investment	Accumulated Other Comprehensive Income (Loss)	Common Stock in Treasury	Total CONSOL Energy Inc. Stockholders’ Equity	Non- Controlling Interest
Balance, Beginning of Period at Dec. 31, 2014	$ 5,006,289	$ 0	$ 0	$ 0	$ 1,525,142	$ (278,950)	$ 0	$ 1,246,192	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	317,421				307,011			307,011	10,410
Actuarially determined long term liability adjustments	(89,442)					(89,442)		(89,442)
Comprehensive (Loss) Income	227,979				307,011	(89,442)		217,569	10,410
Distributions to Noncontrolling Interest	(5,060)								(5,060)
Proceeds from Sale of MLP Interest	148,399								148,399
Net Parent Distributions	(555,671)				(555,671)			(555,671)
Balance, End of Period at Dec. 31, 2015	1,061,839	0	0	0	1,276,482	(368,392)	0	908,090	153,749
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	50,450				41,496			41,496	8,954
Actuarially determined long term liability adjustments	(31,409)					(31,671)		(31,671)	262
Comprehensive (Loss) Income	19,041				41,496	(31,671)		9,825	9,216
Distributions to Noncontrolling Interest	(21,657)								(21,657)
Net Parent Distributions	(260,284)				(260,284)			(260,284)
Amortization of Stock-Based Compensation Awards	1,185								1,185
Balance, End of Period at Dec. 31, 2016	800,124	0	0	0	1,057,694	(400,063)	0	657,631	142,493
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	82,569			(43,713)	111,342			67,629	14,940
Actuarially determined long term liability adjustments	94,919					94,963		94,963	(44)
Comprehensive (Loss) Income	177,488			(43,713)	111,342	94,963		162,592	14,896
Distributions to Noncontrolling Interest	(21,892)								(21,892)
Spin Distribution to CNX Resources	(425,000)				(425,000)			(425,000)
Separation Adjustments			537,028		(537,028)
Issuance of Common Stock	0	280	(280)
Net Parent Distributions	(207,008)				(207,008)			(207,008)
Amortization of Stock-Based Compensation Awards	22,085		16,212					16,212	5,873
Units/Shares Withheld for Taxes	(2,156)		(167)					(167)	(1,989)
Balance, End of Period at Dec. 31, 2017	$ 343,641	$ 280	$ 552,793	$ (43,713)	$ 0	$ (305,100)	$ 0	$ 204,260	$ 139,381