Ceiling Test (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012 Rate	Jun. 30, 2011
Ceiling Test (Textual) [Abstract]
Ceiling test write-downs	$ 53,500,000	$ 20,100,000	$ 13,000,000	$ 5,900,000	$ 53,500,000	$ 13,000,000
Increase (Decrease) in ceiling test write-downs	$ 53,485,000	$ 1,200,000	$ 12,973,000	$ 1,600,000	$ 73,596,000	$ 18,907,000
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		2.97		3.27	2.48	3.40
Barrel of oil [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices		107.99		85.38	106.60	94.00
Mcfe of Ngl [Member]
Ceiling Test (Textual) [Abstract]
Average sales prices		8.74		7.32	7.93	7.81