Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Total Derivative Settlement Gain (Loss)	[1]	$ 112,795	$ (33,680)	$ 274,024	$ (62,620)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net	[2]	80,929	126,469	(73,238)	224,131
Crude oil
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Total Derivative Settlement Gain (Loss)		73,915	(20,160)	180,129	(26,918)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		66,749	93,595	(7,111)	125,545
Natural Gas
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Total Derivative Settlement Gain (Loss)	[3]	38,880	(13,472)	73,112	(26,876)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		6,070	28,154	(76,269)	87,615
Gain on Early Settlement of Derivatives		(15,300)		(15,300)
Natural Gas Liquids
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Total Derivative Settlement Gain (Loss)		0	(48)	20,783	(8,826)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		$ 8,110	$ 4,720	$ 10,142	$ 10,971

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

[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.

[3] Natural gas derivative settlements for the three and six months ended June 30, 2015 include a $15.3 million gain on the early settlement of future contracts as a result of divesting of the Company’s Mid-Continent assets during the second quarter of 2015.