Concentration of Credit Risk (Schedule of Concentration of Credit Risk) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Concentration Risk [Line Items]      
Revenues $ 1,331.8    
Credit Concentration Risk [Member]      
Concentration Risk [Line Items]      
Revenues [1] $ 167.3    
Concentration Risk, Percentage [1] 12.60%    
Predecessor      
Concentration Risk [Line Items]      
Revenues   $ 1,346.9 $ 1,179.4
Predecessor | Credit Concentration Risk [Member]      
Concentration Risk [Line Items]      
Revenues [1]   $ 168.5 $ 167.5
Concentration Risk, Percentage [1]   12.50% 14.20%
[1] Represents the gross amount of revenue contracted for with Columbia Gas of Ohio and, therefore, subject to risk at the loss of this customer. Columbia Gas of Ohio has entered into certain capacity release arrangements with third parties which ultimately can decrease the net revenue amount we receive from Columbia Gas of Ohio in any given period.