Derivative Instruments (Schedule Of Derivative Assets And Liabilities Statement) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Derivative Asset, Fair Value, Gross Asset	$ 5,995	$ 4,848
Derivative Liability, Fair Value, Gross Liability	44,540	49,647
Derivatives Designated as Cash Flow Hedges [Member] | Commodity Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	0	4,539
Derivative Liability, Fair Value, Gross Liability	0	10,128
Derivatives Not Designated as Cash Flow Hedges [Member]
Derivative Asset, Fair Value, Gross Asset	5,995	309
Derivative Liability, Fair Value, Gross Liability	44,540	39,519
Current [Member] | Derivatives Designated as Cash Flow Hedges [Member] | Commodity Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	0	4,065
Derivative Liability, Fair Value, Gross Liability	0	10,065
Current [Member] | Derivatives Not Designated as Cash Flow Hedges [Member] | Interest Rate [Member]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	470
Current [Member] | Derivatives Not Designated as Cash Flow Hedges [Member] | Commodity Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	4,791	0
Derivative Liability, Fair Value, Gross Liability	5,653	0
Current [Member] | Derivatives Not Designated as Cash Flow Hedges [Member] | Ethane - Put Option [Member]
Derivative Asset, Fair Value, Gross Asset	880	309
Derivative Liability, Fair Value, Gross Liability	0	0
Long Term [Member] | Derivatives Designated as Cash Flow Hedges [Member] | Commodity Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	0	474
Derivative Liability, Fair Value, Gross Liability	0	63
Long Term [Member] | Derivatives Not Designated as Cash Flow Hedges [Member] | Commodity Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	324	0
Derivative Liability, Fair Value, Gross Liability	334	0
Long Term [Member] | Derivatives Not Designated as Cash Flow Hedges [Member] | Embedded Derivatives [Member]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	$ 38,553	$ 39,049