Certain provisions of the partnership agreement (Details Textuals) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Distribution Made to Member or Limited Partner [Line Items]
8 7/8% Senior unsecured notes due 2018 (2018 Notes)	8 7/8%	8 7/8%
Percentage Of Cash Avaliable For Distribution	100.00%	100.00%
Number of days from end of quarter for distribution		45 days
Incentive Distribution, Distribution	$ 1.2	$ 3.3
Fortyeight Percent [Member]
Distribution Made to Member or Limited Partner [Line Items]
Percentage Of Distribution Allocated to Common Units	48.00%	48.00%
Common And Preferred [Member] | Twentythree Percent [Member]
Distribution Made to Member or Limited Partner [Line Items]
Percentage Of Distribution Allocated to Common Units	23.00%	23.00%
Incentive Distibution Excess Per Unit Amount		$ 0.3125
Common And Preferred [Member] | Fortyeight Percent [Member]
Distribution Made to Member or Limited Partner [Line Items]
Incentive Distibution Excess Per Unit Amount		$ 0.375
General Partner [Member] | Thirteen Percent [Member]
Distribution Made to Member or Limited Partner [Line Items]
Percentage of distribution allocated to partner	13.00%	13.00%
Incentive Distibution Excess Per Unit Amount		$ 0.25