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								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Distribution Made To Limited Partner [Line Items]
Distributions declared									$ 292.3	$ 203.2		$ 117.4
Income in excess of distributions									3.0	41.7		49.7
Net income attributable to the Partnership	$ 86.4	$ 72.6	$ 65.5	$ 70.8	$ 69.5	$ 56.3	$ 63.8	$ 55.3	$ 295.3	$ 244.9	[1]	$ 167.1	[1]
Weighted average units outstanding (in millions):
Basic and diluted (in shares)									184.1	172.9		143.8
Net income per limited partner unit (in dollars):
Basic and diluted (in dollars per share)	$ 0.35	$ 0.31	$ 0.29	$ 0.33	$ 0.34	$ 0.28	$ 0.35	$ 0.36
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared									$ 64.6	$ 24.2		$ 4.0
Income in excess of distributions									0.0	0.8		1.0
Net income attributable to the Partnership									$ 64.6	$ 25.0		$ 5.0
Weighted average units outstanding (in millions):
Basic and diluted (in shares)									3.7	3.5		2.9
Limited Partners' Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared									$ 227.7	$ 109.8		$ 60.1
Income in excess of distributions									3.0	24.6		25.4
Net income attributable to the Partnership									$ 230.7	$ 134.4		$ 85.5
Weighted average units outstanding (in millions):
Basic and diluted (in shares)									180.4	101.9		73.4
Net income per limited partner unit (in dollars):
Basic and diluted (in dollars per share)									$ 1.28	$ 1.32		$ 1.16
Limited Partner's Subordinated Units
Distribution Made To Limited Partner [Line Items]
Distributions declared									$ 0.0	$ 69.2		$ 53.3
Income in excess of distributions										16.3		23.3
Net income attributable to the Partnership										$ 85.5		$ 76.6
Weighted average units outstanding (in millions):
Basic and diluted (in shares)										67.5		67.5
Net income per limited partner unit (in dollars):
Basic and diluted (in dollars per share)										$ 1.27		$ 1.14

[1] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.