CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (Unaudited) - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	General Partner	Limited Partner Common Units
Beginning balance at Dec. 31, 2016	$ 4,530.9	$ (80.1)	$ 88.8	$ 4,522.2
Add (deduct):
Net income	143.0		2.9	140.1
Distributions paid	(51.1)		(1.0)	(50.1)
Other comprehensive income, net of tax	0.5	0.5
Ending balance at Jun. 30, 2017	4,623.3	(79.6)	90.7	4,612.2
Beginning balance at Dec. 31, 2017	4,724.8	(81.0)	92.7	4,713.1
Add (deduct):
Net income	139.4		2.8	136.6
Distributions paid	(51.1)		(1.0)	(50.1)
Other comprehensive income, net of tax	2.3	2.3
Ending balance at Jun. 30, 2018	4,818.6	$ (78.7)	94.3	4,803.0
Add (deduct):
Cumulative effect adjustment from the implementation of ASC 606	(12.8)		$ (0.2)	(12.6)
Adjustment related to registration rights agreement	$ 16.0			$ 16.0