Significant Accounting Policies (Schedule of Basic and Dilutive Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net Income	$ 17,401	$ 7,024	$ 48,830	$ 20,303	$ 46,034	$ 9,084	$ 52,709	$ 70,958	$ 93,558	$ 178,785	$ 82,569
Less: Net Income Attributable to Noncontrolling Interest	3,455	2,684	5,550	5,868	6,362	3,350	7,547	8,550	17,557	25,809	14,940
Net Income Attributable to CONSOL Energy Inc. Shareholders	$ 13,946	$ 4,340	$ 43,280	$ 14,435	$ 39,672	$ 5,734	$ 45,162	$ 62,408	$ 76,001	$ 152,976	$ 67,629
Denominator:
Weighted-average shares of common stock outstanding (in shares)									26,938,339	27,928,245	27,968,188
Effect of dilutive shares (in shares)									132,769	491,517	206,046
Weighted-average diluted shares of common stock outstanding (in shares)									27,071,108	28,419,762	28,174,234
Earnings per Share:
Basic (in dollars per share)									$ 2.82	$ 5.48	$ 2.42
Dilutive (in dollars per share)									$ 2.81	$ 5.38	$ 2.40