Derivative Financial Instruments Gains and Losses (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivatives Settlement Adjustment	$ 41,000,000
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	12,615,000	[1]	22,062,000	[1]	44,264,000	[1]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	583,264,000	[2]	3,080,000	[2]	55,630,000	[2]
Amount reclassified from AOCIL	0		1,115,000		(2,264,000)
Gain (Loss) on Hedging Activity			(1,800,000)		3,900,000
Crude oil
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	28,410,000		(15,161,000)		(11,893,000)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	457,082,000		(14,665,000)		20,088,000
Natural Gas [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	(26,706,000)		30,338,000		47,270,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	93,267,000		14,053,000		15,493,000
Natural Gas Liquids [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	10,911,000		6,885,000		8,887,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 32,915,000		$ 3,692,000		$ 20,049,000

[1] (1) Total derivative settlement gain is reported in the derivative cash settlements line item on the accompanying statements of cash flows within net cash provided by operating activities with the change in accrued settlements between years being reported in change in accounts receivable and change in accounts payable and accrued expenses line items. Total derivative settlement gains are adjusted by a $41.0 million decrease attributable to the change in current assets and liabilities at December 31, 2014.

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