Derivative Financial Instruments Gains and Losses (Details)		12 Months Ended
		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		$ 0	$ 0	$ 0
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)		512,566,000	12,615,000	22,062,000
Derivative gain		408,831,000	583,264,000	3,080,000
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[1]	0	0	(1,115,000)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[2]	0	0	1,777,000
NYMEX Oil Contracts [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)		362,219,000	28,410,000	(15,161,000)
Derivative gain		191,165,000	457,082,000	(14,665,000)
Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain on Early Settlement of Derivatives		15,300,000	5,600,000
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	[3]	123,180,000	(26,706,000)	30,338,000
Derivative gain		189,734,000	93,267,000	14,053,000
NGL Contracts [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)		27,167,000	10,911,000	6,885,000
Derivative gain		$ 27,932,000	$ 32,915,000	$ 3,692,000
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Number of Instruments Held		0	0	0

[1] Reclassification from accumulated other comprehensive loss related to de-designated hedges. Refer to Note 10 - Derivative Financial Instruments for further information.

[2] As of December 31, 2013, all commodity derivative contracts that had been previously designated as cash flow hedges had settled and had been reclassified into earnings from AOCL.

[3] 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.