Partners' Capital, Mezzanine Equity and Distributions (Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016
Partners Capital And Distributions [Line Items]
Date Paid		Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016
Per Unit Amount		$ 0.7225	$ 0.7200	$ 0.7100	$ 0.7000	$ 0.6900	$ 0.6725
Total Amount		$ 88,563	$ 88,257	$ 83,765	$ 82,585	$ 81,406	$ 73,961
Scenario, Forecast
Partners Capital And Distributions [Line Items]
Date Paid	Nov. 14, 2017
Per Unit Amount	$ 0.5000
Total Amount	$ 61,290