CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 7,024	$ 48,830	$ 20,303	$ 9,084	$ 52,709	$ 70,958	$ 76,157	$ 132,751
Other Comprehensive Income:
Actuarially Determined Long-Term Liability Adjustments (Net of tax: ($780), ($1,232), ($2,342), ($3,697))	2,457	2,459	2,460	4,177	4,182	3,997	7,376	12,356
Unrecognized Loss on Derivatives:
Unrealized Loss on Cash Flow Hedges (Net of tax: $83, $—, $167, $—)	(261)	(264)		0			(525)	0	$ 0
Other Comprehensive Income	2,196			4,177			6,851	12,356
Comprehensive Income	9,220	$ 51,025	$ 22,763	13,261	$ 56,891	$ 74,955	83,008	145,107
Less: Comprehensive Income Attributable to Noncontrolling Interest	2,681			3,346			14,097	19,444
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders	$ 6,539			$ 9,915			$ 68,911	$ 125,663