Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Beginning Balance $ 23.2  
Noncontributed net parent investment adjustments [1] (0.4)  
Accretion expense 0.9  
Additions 0.4  
Settlements 0.0  
Change in estimated cash flows (1.6)  
Ending Balance 22.5  
Predecessor    
Beginning Balance $ 23.2 $ 26.3
Noncontributed net parent investment adjustments [1]   0.0
Accretion expense   1.1
Additions   2.0
Settlements   0.0
Change in estimated cash flows   (0.2)
Ending Balance   $ 29.2
[1] Reflects the removal of amounts related to Crossroads Pipeline Company, which was included in the Predecessor but was not contributed to the Partnership.