Ceiling Test (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2013 Rate	Jun. 30, 2012
Ceiling Test (Textual) [Abstract]
Increase (Decrease) in ceiling test write-downs	$ 0	$ 53,485,000	$ 20,111,000	$ 0	$ 73,596,000
Cash Flow Hedge, Decrease in Impairment of Gas and Oil Properties		$ (1,200,000)
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		2.48	2.97
Barrel of oil [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices		106.60	107.99
Mcfe of Ngl [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices		7.93	8.74