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Equity-Based Awards, Restricted Unit Awards (Details) - Restricted Common Unit Awards [Member] - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting rate of restricted common unit awards 25.00%   25.00%  
Summary of awards activity, equity instruments other than options [Roll Forward]        
Beginning of period (in units)     682,294  
Vested (in units)     (679,370)  
Forfeited (in units)     (1,250)  
End of period (in units) 1,674   1,674  
Restricted 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) [1]     $ 28.61  
Vested weighted-average grant date fair value per unit (in dollars per unit) [1]     28.60  
Forfeited weighted-average grant date fair value per unit (in dollars per unit) [1]     31.07  
Weighted-average grant date fair value per unit, at end of period (in dollars per unit) [1] $ 31.74   $ 31.74  
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]        
Cash distributions paid to restricted common unitholders $ 0.0 $ 0.3 $ 0.3 $ 1.4
Total intrinsic value of our restricted common unit awards that vested during period $ 0.3 $ 0.7 $ 18.9 $ 28.0
[1] Determined by dividing the aggregate grant date fair value of awards (before an allowance for forfeitures) by the number of awards issued.