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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 131.0	$ 113.0	$ 250.0	$ 219.0
Income (less than) / in excess of distributions	(16.0)	(2.0)	(3.0)	(44.0)
Net income attributable to the Partnership	115.0	111.0	247.0	175.0
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared	31.0	32.0	57.0	60.0
Income (less than) / in excess of distributions	(1.0)	0.0	0.0	(1.0)
Net income attributable to the Partnership	30.0	32.0	57.0	59.0
Limited Partners’ Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	100.0	81.0	193.0	159.0
Income (less than) / in excess of distributions	(15.0)	(2.0)	(3.0)	(43.0)
Net income attributable to the Partnership	$ 85.0	$ 79.0	$ 190.0	$ 116.0
Weighted average units outstanding (in millions)
Weighted average units outstanding, basic and diluted (in shares)	226.4	223.8	225.1	216.7
Net income per Limited Partner Unit (in dollars)
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.38	$ 0.35	$ 0.84	$ 0.54