Equity Cash distributions (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 9,688			$ 0	$ 19,117	$ 0
Distribution Made to Limited Partner, Distributions Paid, Per Unit	$ 0.395	$ 0.385	$ 0.224
Distribution Made To Limited Partner Distributions Paid Annualized Per Unit	$ 1.58	$ 1.54	$ 0.896
Distribution Made to Limited Partner, Cash Distributions Paid	9,688	9,429	5,486
Distribution Made to Limited Partner, Distribution Date	Aug. 13, 2013	May 15, 2013	Feb. 14, 2013
Distribution Made to Limited Partner, Date of Record	Aug. 06, 2013	May 07, 2013	Feb. 06, 2013
Managing Member or General Partner, Subsequent Distribution Amount	193			0	382	0
Distributions Per Limited Partnership and General Partnership Unit, Outstanding, Basic	$ 0.395				$ 0.780
Common [Member]
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid	4,755			0	9,375	0
Subordinated Units [Member]
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid	$ 4,740			$ 0	$ 9,360	$ 0