Divestiture (Details) (USD $)	5 Months Ended
	May 31, 2012	May 31, 2011	Dec. 31, 2011	May 25, 2011 MMcf
Divestiture Abstract
Proceeds from sale of oil and gas property and equipment	$ 175,000,000	$ 118,100,000
Divested assets, Production in MMcfe per day	23.0
Divested assets, Proved net reserves in Bcfe			138.0
Divested assets, Haynesville and Middle Bossier Shales, Net acres				9,717
Net production per day of acreage sold in MMcf				7.0
Divested assets, net proved reserves in Bcf				37.1