Net Income Per Limited Partner Unit - Schedule of Basic and Diluted Net Income Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 140.0	$ 121.0	$ 390.0	$ 340.0
Income (less than) / in excess of distributions	1.0	28.0	(2.0)	(16.0)
Net income attributable to the Partnership	141.0	149.0	388.0	324.0
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared	36.0	36.0	93.0	96.0
Income (less than) / in excess of distributions	0.0	1.0	0.0	0.0
Net income attributable to the Partnership	36.0	37.0	93.0	96.0
Limited Partners’ Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	104.0	85.0	297.0	244.0
Income (less than) / in excess of distributions	1.0	27.0	(2.0)	(16.0)
Net income attributable to the Partnership	$ 105.0	$ 112.0	$ 295.0	$ 228.0
Weighted average units outstanding (in millions)
Weighted average units outstanding, basic and diluted (in shares)	233.3	223.8	227.9	219.1
Net income per Limited Partner Unit (in dollars)
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.45	$ 0.50	$ 1.30	$ 1.04