Derivative Activities (Details 2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	$ 65,517	$ 131,450
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	(4,427)	(13,764)
Collars [Member] | Crude Oil [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	(15,830)	0
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	0	(12,051)
Call Option [Member] | Crude Oil [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	(43,675)	(31,904)
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	(7,675)	(28,393)
Collars [Member] | Natural Gas [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	107,258	155,159
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	3,079	27,032
Swap [Member] | Natural Gas [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	4,014	0
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	169	0
Natural Gas [Member] | Basis Swap [Member]
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	0	(352)
Natural Gas [Member] | Collars discontinued operations [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	0	8,195
Swap [Member] | NGL [Member]
Derivative assets:
Derivative Assets - Commodity collars, swaps, basis swaps and call options	13,750	0
Derivative liabilities:
Derivative Liabilities - Commodity collars, swaps, basis swaps and call options	$ 0	$ 0