Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 82,569	$ 50,450	$ 317,421
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits (net of tax: $1,076, $186, and $7,943)	(1,832)	(316)	(13,524)
Curtailment Gain (net of tax: $0, $0, $3,788)	0	0	(6,451)
Recognized Net Actuarial Loss (net of tax: $(9,039), $(8,524), $(43,732))	15,391	14,515	74,463
Settlement Loss (net of tax: $(2,312), $(8,213), $(7,050))	7,841	13,983	12,003
OPEB Plan Amendments (net of tax: $0, $10,420, $116,712)	0	(28,164)	(198,727)
Other Comprehensive Gain (Loss) before Reclassifications (net of tax: $(26,360), $24,232, $(25,916))	73,519	(31,427)	42,794
Other Comprehensive Income (Loss)	94,919	(31,409)	(89,442)
Comprehensive Income	177,488	19,041	227,979
Less: Comprehensive Income Attributable to Noncontrolling Interests	14,896	9,216	10,410
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders	$ 162,592	$ 9,825	$ 217,569