Commitments and Contingencies Additional Information (Details) (USD $)	12 Months Ended			12 Months Ended					12 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 American electric corp [Member]	Dec. 31, 2011 PCB Soil Removal Action	Dec. 31, 2010 PCB Soil Removal Action	Dec. 31, 2009 PCB Soil Removal Action	Dec. 31, 2011 Asbestos Issue [Member]	Dec. 31, 2011 Commonwealth Park Property [Member]	Dec. 31, 2011 South Carolina Electric Gas Company	Mar. 31, 2011 South Carolina Electric Gas Company Counterclaim	Dec. 31, 2011 CNX Gas Stock Acquisition	Dec. 31, 2011 C. L. Ritter [Member] best case scenario [Member]	Dec. 31, 2011 C. L. Ritter [Member] worst case scenario [Member]	Dec. 31, 2011 C.L. Ritter - Similar Lawsuits [Member]	Dec. 31, 2011 C.L. Ritter - Similar Lawsuits [Member] best case scenario [Member]	Dec. 31, 2011 C.L. Ritter - Similar Lawsuits [Member] worst case scenario [Member]	Dec. 31, 2011 Earl Kennedy [Member]
Commitments and Contingencies Disclosure [Line Items]
Loss Contingency, Range of Possible Loss, Portion Not Accrued		$ 1,387,000,000
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				5,000,000	65,000,000				30,000,000	27,000,000
Claims by plaintiff										36000								20000
Loss Contingency, Actions Taken by Defendant											9400
The current estimated cost of the most likely remediation plan for one of the additional areas discovered is approximately					11,000,000				20,000,000			221,000,000
Loss Contingency, Loss in Period						3,502,000	3,422,000
Loss Contingency, Range of Possible Loss, Minimum				2,000,000					9,000,000	16,000,000
CONSOL Energy's portion of probable recoveries from settled claims					4,491,000
Remaining liability in PCB soil removal action		128,247,000	139,079,000		3,468,000
Loss Contingency, Damages Sought, Value				384,000
Commitments and Contingent, number of asbestos claims								7,500,000
Settled claims, damages to be paid	$ 5,500,000				$ 250,000	$ 1,209,000
Allegations by plaintiff									58000				34000	430000	22000	100000	622000
Price per share												$ 38.25