Guarantor Subsidiaries Financial Information (Guarantor Subsidiaries Comprehensive Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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
Condensed Statement of Income Captions [Line Items]
Net Income	$ (24,640)	$ 8,518	$ 52,246	$ 46,445	$ 22,914	$ 4,751	$ 13,901	$ 8,884	$ 82,569	$ 50,450	$ 317,421
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									(1,832)	(316)	(13,524)
Settlement Loss									7,841	13,983	12,003
Net Actuarial Loss (Gain)									94,919	(31,409)	(89,442)
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
Reportable Legal Entities | Parent Issuer
Condensed Statement of Income Captions [Line Items]
Net Income									67,629	41,496	307,011
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									0
Settlement Loss									0
Net Actuarial Loss (Gain)									94,919	(31,409)	(89,442)
Other Comprehensive Income (Loss)									94,919	(31,409)	(89,442)
Comprehensive Income									162,548	10,087	217,569
Less: Comprehensive Income Attributable to Noncontrolling Interests									0	0	0
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders									162,548	10,087	217,569
Reportable Legal Entities | Guarantor
Condensed Statement of Income Captions [Line Items]
Net Income									(137,236)	33,631	312,946
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									0
Settlement Loss									0
Net Actuarial Loss (Gain)									0	0	0
Other Comprehensive Income (Loss)									0	0	0
Comprehensive Income									(137,236)	33,631	312,946
Less: Comprehensive Income Attributable to Noncontrolling Interests									0	0	0
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders									(137,236)	33,631	312,946
Reportable Legal Entities | Non-Guarantor
Condensed Statement of Income Captions [Line Items]
Net Income									(1,995)	(103)	4,192
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									0
Settlement Loss									0
Net Actuarial Loss (Gain)									0	0	0
Other Comprehensive Income (Loss)									0	0	0
Comprehensive Income									(1,995)	(103)	4,192
Less: Comprehensive Income Attributable to Noncontrolling Interests									0	0	0
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders									(1,995)	(103)	4,192
Elimination
Condensed Statement of Income Captions [Line Items]
Net Income									113,707	(50,425)	(371,266)
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									0
Settlement Loss									0
Net Actuarial Loss (Gain)									(1,366)	(818)	1,840
Other Comprehensive Income (Loss)									(1,366)	(818)	1,840
Comprehensive Income									112,341	(51,243)	(369,426)
Less: Comprehensive Income Attributable to Noncontrolling Interests									14,896	9,216	10,410
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders									97,445	(60,459)	(379,836)
CONSOL Coal Resources LP | Reportable Legal Entities | Non-Guarantor
Condensed Statement of Income Captions [Line Items]
Net Income									40,464	25,851	64,538
Other Comprehensive Income (Loss):
Amortization of Prior Service Credits									0
Settlement Loss									0
Net Actuarial Loss (Gain)									1,366	818	(1,840)
Other Comprehensive Income (Loss)									1,366	818	(1,840)
Comprehensive Income									41,830	26,669	62,698
Less: Comprehensive Income Attributable to Noncontrolling Interests									0	0	0
Comprehensive Income Attributable to CONSOL Energy Inc. Shareholders									$ 41,830	$ 26,669	$ 62,698