CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (Unaudited) - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	General Partner	Partners' Capital	Common Units Limited Partner
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
Beginning balance at Mar. 31, 2018	4,784.5	(80.1)	93.9		4,770.7
Add (deduct):
Net income	42.2		0.9		41.3
Distributions paid	(25.5)		(0.5)		(25.0)
Other comprehensive income, net of tax	1.4	1.4
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)
Registration Rights Agreement Adjustment	16.0				$ 16.0
Beginning balance at Dec. 31, 2018	4,861.9	(85.2)		$ 4,947.1
Add (deduct):
Net income	183.8			183.8
Distributions paid	(51.1)			(51.1)
Other comprehensive income, net of tax	2.8	2.8
Ending balance at Jun. 30, 2019	4,997.4	(82.4)		5,079.8
Beginning balance at Mar. 31, 2019	4,945.2	(84.4)		5,029.6
Add (deduct):
Net income	75.7			75.7
Distributions paid	(25.5)			(25.5)
Other comprehensive income, net of tax	2.0	2.0
Ending balance at Jun. 30, 2019	$ 4,997.4	$ (82.4)		$ 5,079.8