CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (Unaudited) - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	Limited Partner Common Units	General Partner
Beginning balance at Dec. 31, 2014	$ 4,102.3	$ (72.8)	$ 4,095.1	$ 80.0
Add (deduct):
Net income	156.4		153.3	3.1
Distributions paid	(76.0)		(74.5)	(1.5)
Sale of common units, net of related transaction costs	113.1		113.1
Capital contribution from general partner	2.3			2.3
Other comprehensive income (loss), net of tax	(2.5)	(2.5)
Ending balance at Sep. 30, 2015	4,295.6	(75.3)	4,287.0	83.9
Add (deduct):
Net income	38.3
Ending balance at Sep. 30, 2015	4,295.6	(75.3)	4,287.0	83.9
Beginning balance at Dec. 31, 2015	4,326.7	(84.3)	4,326.2	84.8
Add (deduct):
Net income	214.0		209.7	4.3
Distributions paid	(76.7)		(75.2)	(1.5)
Other comprehensive income (loss), net of tax	4.1	4.1
Ending balance at Sep. 30, 2016	4,468.1	(80.2)	4,460.7	87.6
Add (deduct):
Net income	47.3
Ending balance at Sep. 30, 2016	$ 4,468.1	$ (80.2)	$ 4,460.7	$ 87.6