Derivative Financial Instruments Gains and Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (loss) gain	$ (28,940)	[1]	$ 11,792	[1]
Gain (Loss) on Derivative Instruments, Net, Pretax	(97,662)	[2]	(30,572)	[2]
Crude oil
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (loss) gain	(6,758)		(277)
Derivative (gain) loss	25,192		3,789
Natural Gas
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (loss) gain	(13,404)		9,824
Derivative (gain) loss	46,057		40,069
Natural Gas Liquids
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative cash settlement (loss) gain	(8,778)		2,245
Derivative (gain) loss	$ (2,527)		$ (1,494)

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

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