Statements of Consolidated and Combined Comprehensive Income - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 5 Months Ended 6 Months Ended
Feb. 11, 2015
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2015
Jun. 30, 2014
Net Income $ 42.7 $ 107.8   $ 196.3 $ 239.0  
Net unrealized gain on cash flow hedges [1]   0.5     0.6  
Other Comprehensive Income, Net of Tax and Transaction Adjustments   0.5     0.6  
Total other comprehensive income 0.1 0.5 [2]   0.5   $ 0.6 [2]
Total comprehensive income subsequent to IPO $ 42.8 108.3   196.8 $ 239.6  
Less: Comprehensive income attributable to noncontrolling interest subsequent to IPO   91.9   167.1    
Comprehensive income attributable to limited partners subsequent to IPO   $ 16.4   $ 29.7    
Predecessor [Member]            
Net Income     $ 59.0     151.5
Net unrealized gain on cash flow hedges [1]     0.2     0.5
Total other comprehensive income [2]     0.2     0.5
Total comprehensive income subsequent to IPO     $ 59.2     $ 152.0
[1] Net unrealized gains on derivatives qualifying as cash flow hedges, net of zero and $0.1 million tax expense in the second quarter of 2015 and 2014, respectively, and $0.1 million and $0.3 million tax expense for the six months ended June 30, 2015 and 2014 respectively.
[2] All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.