Impairments (Details) (USD $)	12 Months Ended							3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Granite Wash	Dec. 31, 2013 Selma Chalk	Dec. 31, 2013 Appalachian	Dec. 31, 2012 Appalachian	Mar. 31, 2012 Marcellus Shale	Dec. 31, 2013 Marcellus Shale	Jun. 30, 2011 Arkoma Basin	Dec. 31, 2012 Arkoma Basin	Dec. 31, 2012 Mississippian Properties
Significant Acquisitions and Disposals [Line Items]
Oil and gas properties	$ 132,224,000	$ 103,417,000	$ 104,688,000	$ 121,800,000	$ 900,000	$ 28,400,000		$ 75,000,000	$ 9,500,000
Other - tubular inventory and well materials	0	1,067,000	0
Total impairments	132,224,000	104,484,000	104,688,000
Impairement of oil and gas properties							$ 26,600,000			$ 71,000,000	$ 71,100,000	$ 6,800,000