Short-Term Notes Payable (Details) (USD $)	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Senior Secured Credit Facility April122016 Member [Member]
Short-term Debt [Line Items]
Credit facility, face amount	$ 1,500,000,000
Additional Capacity Available On Credit Lines At Request	250,000,000
Minimum interest coverage ratio	2.50
Interest coverage ratio	5.80
Maximum leverage ratio	4.75
Current maximum leverage ratio	2.15
Senior secured leverage ratio, maximum	2.00
Borrowings outstanding		155,000,000
Current secured leverage ratio	0.19
Letters of credit outstanding	265,673,000	266,656,000
Borrowings and issuance of letters of credit remaining capacity	1,234,327,000	1,078,344,000
Weighted average interest rate of credit facility		3.80%
Senior Secured Credit Facility, 4 Year, May 6, 2014
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	700,000,000
Borrowings outstanding		129,000,000
Letters of credit outstanding		70,203,000
Borrowings and issuance of letters of credit remaining capacity		500,797,000
Weighted average interest rate of credit facility		2.30%
CNX Gas Senior Secured Credit Facility April122016 Member [Member]
Short-term Debt [Line Items]
Credit facility, face amount	1,000,000,000
Additional Capacity Available On Credit Lines At Request	250,000,000
Minimum interest coverage ratio	3.00
Interest coverage ratio	34.18
Maximum leverage ratio	3.50
Current maximum leverage ratio	0.00
Letters of credit outstanding	70,203,000
Borrowings and issuance of letters of credit remaining capacity	$ 929,797,000