Partners' Capital and Distributions (Schedule Of Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands								6 Months Ended		9 Months Ended	12 Months Ended
	Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016	Feb. 12, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Per Unit Cash Distribution Amount		$ 0.8725	$ 0.8550	$ 0.8375	$ 0.8200	$ 0.8025	$ 0.785	$ 1.7275	$ 1.5875		$ 3.245
Total Cash Distribution to Limited Partners		$ 198,951	$ 194,961	$ 190,769	$ 186,783	$ 182,797	$ 178,808	$ 393,912	$ 361,605		$ 739,157
Scenario, Forecast
Per Unit Cash Distribution Amount	$ 0.89									$ 2.6175
Total Cash Distribution to Limited Partners	$ 202,942									$ 596,854