Derivative Activities (Details 1) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Derivative Fair Value Income
Hedge ineffectiveness - realized	$ 2,036		$ 4,558	$ (352)
Hedge ineffectiveness - unrealized	(3,971)	2,389	2,531	2,400
Change in fair value of derivatives that do not qualify for hedge accounting	58,990	(18,284)	67,093	23,885
Realized gain on settlements - gas	5,334	10,179	8,424	17,230
Realized gain (loss) on settlements - oil	285		(7,727)
Realized gain on settlements - NGLs	3,088		3,088
Realized gain on early settlement of oil derivatives		15,697		15,697
Derivative fair value income	$ 65,762	$ 9,981	$ 77,967	$ 58,860