Derivative Financial Instruments Fair Value (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
Fair value of derivative assets and liabilities
Price Risk Derivatives, at Fair Value, Net	$ 585,100,000		$ 592,100,000
Derivative asset current	380,633,000		402,668,000
Derivative asset noncurrent	204,841,000		189,540,000
Derivative assets not designated as hedging instruments	585,474,000		592,208,000
Derivatives liability noncurrent	398,000		70,000
Derivative Liability, Fair Value, Gross Liability	(398,000)		(70,000)
Derivatives not designated as hedging instruments
Fair value of derivative assets and liabilities
Derivative asset current	380,633,000		402,668,000
Derivative asset noncurrent	204,841,000		189,540,000
Derivative liability current	0		0
Derivatives liability noncurrent	398,000		70,000
Level 2 | Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member]
Fair value of derivative assets and liabilities
Derivative assets not designated as hedging instruments	585,474,000	[1]	592,208,000	[1]
Derivative Liability, Fair Value, Gross Liability	$ 398,000	[1]	$ 70,000	[1]

[1] This represents a financial asset or liability that is measured at fair value on a recurring basis.