Distributions (Schedule Of Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands										9 Months Ended		12 Months Ended
	Nov. 13, 2015	[1]	Aug. 14, 2015	May. 15, 2015	Feb. 13, 2015	Nov. 14, 2014	Aug. 14, 2014	May. 15, 2014	Feb. 14, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Per Unit Cash Distribution Amount			$ 0.7400	$ 0.7175	$ 0.6950	$ 0.6675	$ 0.64	$ 0.6125	$ 0.585	$ 2.1525	$ 1.8375		$ 2.505
Total Cash Distribution to Limited Partners			$ 168,296	$ 163,178	$ 158,061	$ 151,568	$ 145,324	$ 139,079	$ 132,835	$ 489,535	$ 417,238		$ 568,806
Scenario, Forecast
Per Unit Cash Distribution Amount	$ 0.7625											$ 2.915
Total Cash Distribution to Limited Partners	$ 173,413											$ 662,948

[1] Our general partner's board of directors declared this cash distribution on October 22, 2015 to be paid on November 13, 2015 to unitholders of record at the close of business on November 2, 2015.