Derivatives (Effect Of Derivative Instruments Recognized In Statement Of Operatio, Not Designated As Hedging Instruments) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedges	$ 6,586,000		$ (18,366,000)
Not Designated as Hedging Instrument [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedges	6,586,000		(18,366,000)
Amount of gain (loss) settled during the period	11,000,000		(8,900,000)
Gain (loss) on derivatives not designated as hedges [Member] | Not Designated as Hedging Instrument [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedges	$ 6,586,000	[1]	$ (18,366,000)	[1]

[1] Amounts settled during the 2015 and 2014 periods include a gain of $11.0 million and a loss of $8.9 million, respectively.