Derivative Financial Instruments Gains and Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (gain) loss	$ 274	[1]	$ 1,288	[1]	$ 62,894	[1]	$ (12,715)	[1]
Derivative (gain) loss	(190,661)	[2]	39,933	[2]	33,470	[2]	(14,685)	[2]
Crude oil
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (gain) loss	517		13,538		27,435		13,786
Derivative (gain) loss	(141,429)		30,488		(42,802)		8,233
Natural Gas
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (gain) loss	1,687		(11,019)		28,563		(18,752)
Derivative (gain) loss	(43,039)		(2,264)		17,700		(12,462)
Natural Gas Liquids
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (gain) loss	(1,930)		(1,231)		6,896		(7,749)
Derivative (gain) loss	$ (6,467)		$ 10,421		$ (4,322)		$ 2,259

[1] (1) Total derivative cash settlement (gain) loss is reported in the derivative cash settlement gain (loss) line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.

[2] (2) Total derivative (gain) loss is reported in the derivative (gain) loss line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.