RELATED PARTY TRANSACTIONS - Narrative (Details)	1 Months Ended			3 Months Ended		12 Months Ended
	Oct. 31, 2017 shares	Sep. 30, 2016 USD ($) $ / shares shares	Jul. 31, 2015 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) business	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017	Nov. 28, 2017 USD ($)
Related Party Transaction [Line Items]
Separation and distribution costs						$ 40,545,000
Payment of separation and distribution costs				$ 18,234,000
Number of independent businesses | business				2
Origination fees				$ 1,170,000	$ 0
Net proceeds from initial public offering			$ 342,711,000
Undivided interest (as a percent)							75.00%
Net payable				0		0
CONSOL Thermal Holdings LLC
Related Party Transaction [Line Items]
Undivided interest (as a percent)		5.00%
Cash consideration		$ 21,500,000
Equity consideration		$ 67,300,000
Weighted average trading price (in dollars per share) | $ / shares		$ 14.79
Price premium (as a percent)		15.00%
CONSOL Coal Resources LP
Related Party Transaction [Line Items]
Net payable				935,000		3,071,000
Preferred Class A | CONSOL Thermal Holdings LLC
Related Party Transaction [Line Items]
Preferred units issued (in shares) | shares	3,956,496	3,956,496
Issue price (in dollars per share) | $ / shares		$ 17.01
Senior Secured Revolving Credit Facility | Line of Credit
Related Party Transaction [Line Items]
Maximum borrowing capacity			400,000,000
Initial draw on line of credit			200,000,000
Origination fees			3,000,000
Net proceeds line of credit			$ 197,000,000
CNX Resources Corporation
Related Party Transaction [Line Items]
Accounts payable, related parties				1,003,000		12,540,000
Accounts receivable, related parties				11,134,000		15,415,000
Other Receivables - Related Party				4,845,000		4,500,000
Accounts receivable, related parties, noncurrent				6,289,000		$ 10,915,000
CNX Coal Resources LP
Related Party Transaction [Line Items]
Units sold in initial public offering (in shares) | shares			5,000,000
Initial public offering share price (in dollars per share) | $ / shares			$ 15.00
Net proceeds initial public offering			$ 75,000,000
Over-allotment option (in shares) | shares			561,067
Affiliated Entity | Affiliated Company Credit Agreement | CONSOL Coal Resources LP
Related Party Transaction [Line Items]
Maximum borrowing capacity								$ 275,000,000
Line of credit amount drawn								$ 201,000,000
Stated interest rate (as a percent)								4.25%
Interest expense				$ 2,134,000