Note 5 - Stock, Unit and Debt Repurchases (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2020	Jul. 31, 2019	Jun. 30, 2019	May 31, 2019	Jul. 31, 2018	Dec. 31, 2017	Nov. 30, 2017
Stock Repurchase Program, Authorized Amount								$ 50,000
Stock and Debt Repurchase Program, Authorized Amount										$ 100,000
Shares repurchased (in shares)	[1]		(0)	1,717,497	708,245
Weighted Average [Member]
Share Price (in dollars per share)				$ 19.06	$ 36.48
CONSOL Coal Resources L P [Member]
Stock Purchased During Period, Affiliated Entity Units (in shares)		0	0	26,297	167,958
Stock Purchased, Affiliated Entity, Average Cost Per Share (in dollars per share)				$ 14.05	$ 18.33
CONSOL Coal Resources L P [Member]
Stock and Debt Repurchase Program, Authorized Amount						$ 270,000	$ 200,000
Stock and Debt Repurchase Program, Additional Authorized Amount						$ 70,000	$ 25,000
Stock and Debt Repurchase Program, Restricted Authorized Amount									$ 50,000
CONSOL Coal Resources L P Units Member
Stock and Debt Repurchase Program, Authorized Amount									175,000
Stock and Debt Repurchase Program, Additional Authorized Amount									75,000	$ 25,000
Stock and Debt Repurchase Program, Restricted Authorized Amount									$ 50,000
Senior Secured Second Lien Notes due 2025 [Member]
Debt Instrument, Repurchase Amount			$ 54,481	$ 52,648	$ 25,724
Senior Notes [Member] | Senior Secured Second Lien Notes due 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage			11.00%	11.00%						11.00%	11.00%	11.00%

[1] See Note 5 - Stock, Unit and Debt Repurchases for additional information.