Partners' Capital, Equity and Incentive Compensation Plans (Schedule of Quarterly Cash Dividends) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Partners' Capital, Equity and Incentive Compensation Plans [Abstract]
Record Date	Sep. 18, 2015	Jun. 19, 2015	Mar. 20, 2015	Dec. 19, 2014	Sep. 19, 2014	Jun. 20, 2014	Mar. 20, 2014	Dec. 20, 2013
Payment Date	Oct. 06, 2015	Jul. 08, 2015	Apr. 07, 2015	Jan. 07, 2015	Oct. 07, 2014	Jul. 08, 2014	Apr. 08, 2014	Jan. 07, 2014
Per Common Share and Per Unit Rate	$ 0.32	$ 0.32	$ 0.32	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.24	[1]	$ 0.29	$ 1.25	$ 1.11
Dividend/Distribution Amount	$ 15.3	$ 15.3	$ 13.4	$ 10.7	$ 10.5	$ 10.9	$ 10.8	$ 9.0			$ 54.7	$ 41.2

[1] The per common share and per unit rate is prorated. It covers the period beginning October 15, 2013 (the closing date of the IPO) through December 31, 2013 and is based on a full quarter distribution of $0.29 per common share and per unit.