Ceiling Test Write-downs (Details) (USD $)	3 Months Ended			4 Months Ended	12 Months Ended
	Dec. 31, 2013	Jun. 30, 2012	Mar. 31, 2012	Oct. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Ceiling Test (Textual) [Abstract]
Increase (Decrease) in ceiling test write-downs	$ 28,100,000	$ 53,500,000	$ 20,100,000	$ 35,400,000	$ 0	$ 137,100,000	$ 18,907,000
Cash Flow Hedge, Decrease in Impairment of Gas and Oil Properties					$ (2,200,000)	$ (3,900,000)
Mcf of natural gas [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices					2.21
Barrel of oil [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices					102.81
Mcfe of Ngl [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices					6.07