Derivative Instruments (Schedule Of Derivative Assets And Liabilities Statement) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative asset, fair value, gross asset	$ 16,233	$ 4,848
Derivative liability, fair value, gross liability	30,757	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	16,233	309
Derivative liability, fair value, gross liability	30,757	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] | Commodity derivatives [Member]
Derivative asset, fair value, gross asset	12,838	0
Derivative liability, fair value, gross liability	113	0
Current [Member] | Derivatives not designated as cash flow hedges [Member] | Ethane - put option [Member]
Derivative asset, fair value, gross asset	1,523	309
Derivative liability, fair value, gross liability	0	0
Current [Member] | Derivatives not designated as cash flow hedges [Member] | Interest rate swap contracts [Member]
Derivative asset, fair value, gross asset	0	0
Derivative liability, fair value, gross liability	0	470
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	1,872	0
Derivative liability, fair value, gross liability	0	0
Long Term [Member] | Derivatives not designated as cash flow hedges [Member] | Embedded derivatives in Series A Preferred Units [Member]
Derivative asset, fair value, gross asset	0	0
Derivative liability, fair value, gross liability	$ 30,644	$ 39,049