Fair Value (Tables)
 6 Months Ended
Jun. 30, 2015
Fair Value Disclosures [Abstract]  
Carrying Amount And Estimated Fair Values Of Financial Instruments
 
(in millions)
Carrying
Amount as of
June 30, 2015
 
Estimated Fair
Value as of
June 30, 2015
 
Carrying
Amount as of
Dec. 31, 2014
 
Estimated Fair
Value as of
Dec. 31, 2014
 
 
 
 
 
Predecessor
Current portion of long-term debt-affiliated
$
—

 
$
—

 
$
115.9

 
$
120.0

Long-term debt-affiliated
630.9

 
630.9

 
1,472.8

 
1,550.4