Ceiling Test (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Ceiling Test (Textual) [Abstract]
Increase (Decrease) in ceiling test write-downs	$ 0	$ 35,391,000	$ 0	$ 108,987,000
Cash Flow Hedge, Decrease in Impairment of Gas and Oil Properties		$ (2,100,000)
Ceiling Test (Additional Textual) [Abstract]
Rate for discounting future cash flows			10.00%
Mcf of natural gas [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices			2.22
Barrel of oil [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices			104.83
Mcfe of Ngl [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices			7.44