CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (Unaudited) - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	Limited Partner Common Units	General Partner	Partners' Capital
Beginning balance at Dec. 31, 2016	$ 4,530.9	$ (80.1)	$ 4,522.2	$ 88.8
Add (deduct):
Net income	212.8		208.6	4.2
Distributions paid	(76.7)		(75.2)	(1.5)
Other comprehensive income, net of tax	1.2	1.2
Ending balance at Sep. 30, 2017	4,668.2	(78.9)	4,655.6	91.5
Beginning balance at Dec. 31, 2017	4,724.8	(81.0)	4,713.1	92.7
Add (deduct):
Net income	177.3		136.6	2.8	$ 37.9
Distributions paid	(76.7)		(50.1)	(1.0)	(25.6)
Other comprehensive income, net of tax	2.4	2.4
General Partner purchase of common units and conversion to partnership interests	0.0		(4,803.0)	(94.3)	4,897.3
Ending balance at Sep. 30, 2018	4,831.0	$ (78.6)	0.0	0.0	$ 4,909.6
Add (deduct):
Cumulative effect adjustment from the implementation of ASC 606	(12.8)		(12.6)	$ (0.2)
Adjustment related to registration rights agreement	$ 16.0		$ 16.0