Acquisitions (Details) (USD $)	12 Months Ended			0 Months Ended		0 Months Ended		12 Months Ended	0 Months Ended	3 Months Ended
	Dec. 31, 2013 Mcfe	Dec. 31, 2012	Dec. 31, 2011	May 04, 2011 7.76% notes, due 2012 thru 2016	Dec. 31, 2011 7.76% notes, due 2012 thru 2016	Jun. 03, 2013 Chesapeake acre	Jun. 03, 2013 Chesapeake Marcellus item Mcfe acre	Dec. 31, 2013 Chesapeake Marcellus	May 04, 2011 Appalachian Natural Gas Trust	Jun. 30, 2011 Appalachian Natural Gas Trust	Dec. 31, 2000 Appalachian Natural Gas Trust	May 04, 2011 Appalachian Natural Gas Trust Class A interest
Acquisitions
Approximate area of acquisition (in acres)						99,000	67,000
Number of wells acquired							10
Purchase price of acquisition						$ 114,200,000
Purchase price of acquisition allocated to undeveloped acreage	95,861,000	117,654,000	41,085,000			57,200,000
Purchase price of acquisition allocated to acquired wells	90,390,000	16,965,000	108,717,000				57,000,000	57,000,000
Portion unlikely to be developed (in acres)							42,000
Addition in sales volume (in Bcfe)							1,700,000
Acquisition of proved developed reserves (Bcfe)	39,700,000						53,500,000
Proceeds from sale of net profits interest (NPI) in certain producing properties											298,000,000
Percentage of net profits received by ANGT											100.00%
Ownership percentage												100.00%
Debt instrument, stated interest rate percentage					7.76%
Additional borrowing				57,100,000
Fair value of notes	2,800,000,000	2,900,000,000		64,200,000
Pre-tax gain on revaluation of existing equity investment in acquiree										10,100,000
Derecognition of post revaluation of oil and gas properties									140,600,000
Derecognition of post revaluation of equity investment in ANGT									48,000,000
Net increase in liabilities									92,600,000
Liability for discounted sales									16,400,000
Recognition of a derivative liability for swap									$ 12,700,000