PROPOSED MERGER (Details) - USD ($) $ / shares in Units, $ in Millions	Aug. 20, 2024	Sep. 30, 2024	Dec. 31, 2023
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Arch Resources, Inc
Business Acquisition [Line Items]
Common Stock Portion, number of Consol Energy's stock for each share of Arch Resources, Inc common stock converted (in shares)	1.326
Business combination, termination fee	$ 82.0
Business combination, expense reimbursement	$ 23.5
Arch Resources, Inc | Common Class A | Arch Resources, Inc
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.01
Arch Resources, Inc | Common Class B | Arch Resources, Inc
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.01