Equity-Based Awards, Phantom Unit Awards (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Cash payments made in connection with DERs				$ 8.6	$ 7.2
Phantom Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate of phantom unit awards		25.00%		25.00%
Summary of awards activity, equity instruments other than options [Roll Forward]
Beginning of period (in units)				9,289,501
Granted (in units)	[1]			4,967,681
Vested (in units)				(3,285,976)
Forfeited (in units)				(216,897)
End of period (in units)		10,754,309		10,754,309
Phantom units outstanding, weighted-average grant date fair value [Roll Forward]
Weighted-average grant date fair value per unit, at beginning of period (in dollars per unit)	[2]			$ 27.65
Granted weighted-average grant date fair value per unit (in dollars per unit)	[1],[2]			26.81
Vested weighted-average grant date fair value per unit (in dollars per unit)	[2]			28.58
Forfeited weighted-average grant date fair value per unit (in dollars per unit)	[2]			26.92
Weighted-average grant date fair value per unit, at end of period (in dollars per unit)	[2]	$ 26.99		$ 26.99
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Aggregate grant date fair value				$ 133.2
Estimated forfeiture rate				3.20%
Cash payments made in connection with DERs		$ 4.7	$ 4.0	$ 8.6	7.2
Total intrinsic value of phantom unit awards that vested during period		3.1	$ 3.1	85.1	$ 66.3
Unrecognized Compensation Expense [Abstract]
Unrecognized compensation cost		158.8		$ 158.8
Recognition period for total unrecognized compensation cost				2 years 2 months 12 days
Phantom Unit Awards [Member] | Minimum [Member]
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Grant date market price of common units (in dollars per unit)				$ 25.40
Phantom Unit Awards [Member] | Maximum [Member]
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Grant date market price of common units (in dollars per unit)				$ 28.18
Phantom Unit Awards [Member] | Enterprise [Member]
Unrecognized Compensation Expense [Abstract]
Unrecognized compensation cost		$ 134.2		$ 134.2

[1] The aggregate grant date fair value of phantom unit awards issued during 2018 was $133.2 million based on a grant date market price of our common units ranging from $25.40 to $28.18 per unit. An estimated annual forfeiture rate of 3.2% was applied to these awards.

[2] Determined by dividing the aggregate grant date fair value of awards (before an allowance for forfeitures) by the number of awards issued.