Basis of Presentation and Significant Accounting Policies (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended					9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Basis of Presentation and Significant Accounting Policies (Details)
Restricted common units excluded from computation of net income per unit	102,559				0	110,366	0
Accumulated Other Comprehensive Income [Table]
Balance, beginning of period	$ 879		$ 902	$ 728	$ 1,018	$ 902	$ 495
Foreign currency translation adjustment, net of tax of $0 and $0, respectively, in 2012 and $0 and $490, respectively in 2011	135				(290)	112	233
Balance, end of period	1,014	879		902	728	1,014	728
Accumulated Other Comprehensive Income (Parentheticals)
Foreign currency translation adjustment, taxes	$ 0				$ 0	$ 0	$ 490
Distribution declaration date	Oct. 18, 2012	Jul. 19, 2012	Apr. 20, 2012	Jan. 20, 2012
Amount of declared distribution	$ 0.3975	$ 0.3875	$ 0.3875	$ 0.3875
Amount of declared distribution on an annualized basis	$ 1.59	$ 1.55	$ 1.55	$ 1.55
Distribution payment date	Nov. 15, 2012	Aug. 15, 2012	May 15, 2012	Feb. 15, 2012
Distribution record date	Nov. 01, 2012	Aug. 01, 2012	May 01, 2012	Feb. 01, 2012