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Equity-Based Awards, Phantom Unit Awards (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]        
Cash payments made in connection with DERs     $ 11.2 $ 8.5
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)     7,767,501  
Granted (in units) [1]     4,259,620  
Vested (in units)     (2,417,571)  
Forfeited (in units)     (209,633)  
End of period (in units) 9,399,917   9,399,917  
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]     $ 27.20  
Granted weighted-average grant date fair value per unit (in dollars per unit) [1],[2]     28.84  
Vested weighted-average grant date fair value per unit (in dollars per unit) [2]     28.31  
Forfeited weighted-average grant date fair value per unit (in dollars per unit) [2]     27.57  
Weighted-average grant date fair value per unit, at end of period (in dollars per unit) [2] $ 27.65   $ 27.65  
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]        
Aggregate grant date fair value     $ 122.9  
Estimated forfeiture rate     3.80%  
Cash payments made in connection with DERs $ 4.0 $ 3.2 $ 11.2 8.5
Total intrinsic value of phantom unit awards that vested during period 1.6 $ 3.0 67.9 $ 40.1
Unrecognized Compensation Expense [Abstract]        
Unrecognized compensation cost 117.5   $ 117.5  
Recognition period for total unrecognized compensation cost     2 years 1 month 6 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)     $ 26.40  
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)     $ 28.87  
Phantom Unit Awards [Member] | Enterprise [Member]        
Unrecognized Compensation Expense [Abstract]        
Unrecognized compensation cost $ 100.0   $ 100.0  
[1] The aggregate grant date fair value of phantom unit awards issued during 2017 was $122.9 million based on a grant date market price of our common units ranging from $26.40 to $28.87 per unit. An estimated annual forfeiture rate of 3.8 percent 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.