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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Partners' Capital, Equity and Incentive Compensation Plans [Abstract]
Record Date		Jun. 17, 2016	Mar. 18, 2016	Dec. 17, 2015	Sep. 18, 2015	Jun. 19, 2015	Mar. 20, 2015	Dec. 19, 2014	Sep. 20, 2016
Payment Date		Jul. 06, 2016	Apr. 05, 2016	Jan. 06, 2016	Oct. 06, 2015	Jul. 08, 2015	Apr. 07, 2015	Jan. 07, 2015	Oct. 05, 2016
Per Common Share and Per Unit Rate	$ 0.36	$ 0.36	$ 0.36	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.29	$ 1.40	$ 1.25
Dividend/Distribution Amount	$ 19.7	$ 19.7	$ 17.4	$ 15.4	$ 15.3	$ 15.3	$ 13.4	$ 10.7	$ 72.2	$ 54.7