Commitments and Contingencies Additional Information (Details) (USD $)				3 Months Ended				3 Months Ended	12 Months Ended	3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Subsidiaries	Mar. 31, 2013 Commonwealth Park Property	Mar. 31, 2013 South Carolina Electric Gas Company [Member]	Mar. 31, 2012 South Carolina Electric Gas Company [Member] Counterclaim [Member]	Mar. 31, 2013 PCB Soil Removal Action	Mar. 31, 2013 American electric corp [Member]	Dec. 31, 2012 American electric corp [Member]	Dec. 31, 2007 Earl Kennedy	Mar. 31, 2013 Cnx Gas Stock Acquisition [Member]	Dec. 31, 2012 Cnx Gas Stock Acquisition [Member]	Mar. 31, 2013 Ratliff [Member]
Commitments and Contingencies Disclosure [Line Items]
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 845,000,000
Claims by plaintiff				The Commonwealth claimed that the Company is liable for dam reconstruction costs, lake restoration costs and natural resource damages totaling $58,000.	36000					The complaint, as amended, seeks injunctive relief, including removing CNX Gas Company from the property, and compensatory damages of $20,000.			$4,000 to $8,000
The current estimated cost of remedial action for the area CONSOL Energy was originally named a PRP, including payment of the EPA's past and future cost, is approximately				30,000,000			65,000,000	5,400,000			20,200
Litigation Settlement, Gross									250
Counterclaim by the company						9400		408
Sale of Stock, Price Per Share												$ 38.25
Loss Contingency, Settlement Agreement, Court											42730
Loss Contingency, Estimate of Possible Loss				20,000,000			11,000,000
Loss Contingency, Range of Possible Loss, Minimum				9,000,000				2,000,000
CONSOL Energy's portion of probable recoveries from settled claims							4,393,000
Remaining liability in PCB soil removal action	839,294,000	768,494,000					3,167,000
Loss Contingency, Damages Sought, Value								$ 384,000
Commitments and Contingent, number of asbestos claims			6,900