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, 2017	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 77.4	$ 53.9		$ 209.2		$ 144.6
Income (less than) / in excess of distributions	(4.8)	2.4		(0.3)		30.8
Net income attributable to the Partnership	72.6	56.3	[1]	208.9	[2]	175.4	[1]
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared	17.7	7.1		44.0		14.7
Income (less than) / in excess of distributions	(0.1)	0.1		0.0		0.6
Net income attributable to the Partnership	17.6	7.2		44.0		15.3
Limited Partners' Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	59.7	29.0		165.2		79.4
Income (less than) / in excess of distributions	(4.7)	1.4		(0.3)		18.0
Net income attributable to the Partnership	$ 55.0	$ 30.4		$ 164.9		$ 97.4
Weighted average units outstanding (in millions):
Weighted average units outstanding, basic and diluted (in shares)	179.2	109.8		178.0		99.2
Net income per Limited Partner Unit (in dollars):
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.31	$ 0.28	[1]	$ 0.93	[2]	$ 0.98	[1]
Limited Partner's Subordinated Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 0.0	$ 17.8		$ 0.0		$ 50.5
Income (less than) / in excess of distributions		0.9				12.2
Net income attributable to the Partnership		$ 18.7				$ 62.7
Weighted average units outstanding (in millions):
Weighted average units outstanding, basic and diluted (in shares)		67.5				67.5
Net income per Limited Partner Unit (in dollars):
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.00	$ 0.28	[1]	$ 0.00	[2]	$ 0.93	[1]

[1] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.

[2] The financial information for the nine months ended September 30, 2017 reflects adjustments for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations from January 1, 2017 through May 9, 2017.