Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized gain on derivatives	$ 4,713	$ 952	$ 7,776	$ 2,802
Unrealized (loss) gain on derivatives	15,114	332	11,844	(1,336)
Total	19,827	1,284	19,620	1,466
Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized gain on derivatives	4,713	952	7,776	2,802
Unrealized (loss) gain on derivatives	15,114	332	11,844	(1,336)
Oil [Member] | Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized gain on derivatives	719		719
Unrealized (loss) gain on derivatives	20,483		15,223
Natural Gas [Member] | Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized gain on derivatives	3,994	952	7,057	2,802
Unrealized (loss) gain on derivatives	$ (5,369)	$ 332	$ (3,379)	$ (1,336)