Derivative Financial Instruments Gains and Losses (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement (Gain) Loss		$ (329,478)	$ (512,566)	$ (12,615)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		250,633	(408,831)	(583,264)
NYMEX Oil Contracts [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement (Gain) Loss		(243,102)	(362,219)	(28,410)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		85,370	(191,165)	(457,082)
Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain on Early Settlement of Derivatives			15,300	5,600
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement (Gain) Loss	[1]	(94,936)	(123,180)	26,706
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		81,060	(189,734)	(93,267)
NGL Contracts [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement (Gain) Loss		8,560	(27,167)	(10,911)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net		$ 84,203	$ (27,932)	$ (32,915)
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Number of Instruments Held		0	0	0

[1] Natural gas derivative settlements for the years ended December 31, 2015, and 2014, include $15.3 million and $5.6 million, respectively, of early settlements of futures contracts as a result of divesting assets in the Company’s Mid-Continent region.