Partners' Capital (Schedule of Partners' Capital Account, Distriubtions) (Details) - USD ($) $ / shares in Units, $ in Millions									6 Months Ended
	May 15, 2017	May 08, 2017	Feb. 14, 2017	Feb. 07, 2017	May 13, 2016	May 06, 2016	Feb. 12, 2016	Feb. 05, 2016	Jun. 30, 2017	Jun. 30, 2016
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Date of Record		May 08, 2017		Feb. 07, 2017		May 06, 2016		Feb. 05, 2016
Distribution Made to Limited Partner, Distribution Date	May 15, 2017		Feb. 14, 2017		May 13, 2016		Feb. 12, 2016
Distribution Made to Member or Limited Partner, Distributions Paid, Per Unit	$ 0.60		$ 0.6		$ 0.60		$ 1.375
Distribution Made to Limited Partner, Cash Distributions Paid	$ 41.8		$ 41.8		$ 41.4		$ 95.6		$ 83.6	$ 137.0