Derivative Instruments and Hedging Activities (Summary Of Balance Sheet Locations And Related Fair Values Of Outstanding Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Commodity price swaps	$ 1,670
Derivative Asset, Fair Value, Gross Liability	0
Derivative, Fair Value, Net	1,670
Derivative Liability, Fair Value, Gross Liability	65,375	41,258
Commodity price swap contracts, Fair Value	(23,679)	(17,383)
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value	41,696	23,875
Derivative Instrument not Designated as Hedging Instrument Asset Position - Gross Asset	6,972
Derivative Instrument Not Designated as Hedging Instrument in Asset Position - Asset	6,972
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	(12,611)
Derivatives not designated as hedge liability, Fair Value	10,724	51,717
Derivative Asset	8,642
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	52,420	75,592
Derivative Liability, Current	26,843	62,388
Derivative Liability, Noncurrent	25,577	13,204
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Commodity price swaps	1,670
Derivative Asset, Fair Value, Gross Liability	0
Derivative, Fair Value, Net	1,670
Derivative Liability, Fair Value, Gross Liability	1,814	3,430
Commodity price swap contracts, Fair Value	0	0
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value	1,814	3,430
Nymex Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Instrument not Designated as Hedging Instrument Asset Position - Gross Asset	0
Derivative Instrument not Designated as Hedging Instrument Asset Position - Liability	0
Derivative Instrument Not Designated as Hedging Instrument in Asset Position - Asset	0
Derivative Instrument Not Designated as Hedging Instrument - Gross Liability	3,569	5,563
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	0
Derivatives not designated as hedge liability, Fair Value	3,569	5,563
Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Instrument Not Designated as Hedging Instrument - Gross Liability	23,335	51,717
Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Instrument not Designated as Hedging Instrument Asset Position - Liability	0
Prepayments and other
Derivatives, Fair Value [Line Items]
Derivative Asset	6,972
Other Intangible Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1,670
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Commodity price swaps	0
Derivative Asset, Fair Value, Gross Liability	0
Derivative, Fair Value, Net	0
Derivative Liability, Fair Value, Gross Liability	63,561	37,828
Commodity price swap contracts, Fair Value	(23,679)	(17,383)
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value	39,882	20,445
Derivative Instrument not Designated as Hedging Instrument Asset Position - Gross Asset	6,972
Derivative Instrument not Designated as Hedging Instrument Asset Position - Liability	0
Derivative Instrument Not Designated as Hedging Instrument in Asset Position - Asset	6,972
Derivative Instrument Not Designated as Hedging Instrument - Gross Liability	19,766	46,154
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	(12,611)
Derivatives not designated as hedge liability, Fair Value	$ 7,155	$ 46,154