Partners' Capital and Distributions (Schedule Of Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands									9 Months Ended		12 Months Ended
	Nov. 14, 2018	Aug. 14, 2018	May 15, 2018	Feb. 14, 2018	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Distribution Made to Limited Partner [Line Items]
Cash distribution per unit (in dollars per share)		$ 0.9575	$ 0.9375	$ 0.9200	$ 0.9050	$ 0.8900	$ 0.8725	$ 0.855	$ 2.815	$ 2.6175		$ 3.5225
Total Cash Distribution to Limited Partners		$ 218,497	$ 213,933	$ 209,940	$ 206,362	$ 202,942	$ 198,951	$ 194,961	$ 642,370	$ 596,854		$ 803,216
Scenario, Forecast
Distribution Made to Limited Partner [Line Items]
Cash distribution per unit (in dollars per share)	$ 0.9775										$ 3.7925
Total Cash Distribution to Limited Partners	$ 223,061										$ 865,431