Statements of Consolidated and Combined Comprehensive Income - USD ($)
$ in Millions
 1 Months Ended 11 Months Ended 12 Months Ended
Feb. 11, 2015
Dec. 31, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Net Income $ 42.7 $ 487.5 $ 530.2    
Net unrealized gain on cash flow hedges [1]     1.5    
Unrecognized pension and OPEB costs [2]     (0.2)    
Other Comprehensive Income, Net of Tax and Transaction Adjustments     1.3    
Total comprehensive income 42.8 488.7 531.5    
Total comprehensive income $ 0.1 1.2 $ 1.3 [3]    
Less: Comprehensive income attributable to noncontrolling interest subsequent to IPO   414.5      
Comprehensive income attributable to limited partners subsequent to IPO   $ 74.2      
Predecessor          
Net Income       $ 269.1 $ 266.9
Net unrealized gain on cash flow hedges [1]       1.0 1.1
Unrecognized pension and OPEB costs [2]       0.0 0.0
Other Comprehensive Income, Net of Tax and Transaction Adjustments       1.0 1.1
Total comprehensive income       270.1 268.0
Total comprehensive income [3]       $ 1.0 $ 1.1
[1] Net unrealized gain on derivatives qualifying as cash flow hedges, net of $0.1 million, $0.7 million and $0.6 million tax expense in 2015, 2014 and 2013, respectively.
[2] Unrecognized pension and OPEB costs, net of zero tax expense in 2015, 2014 and 2013, respectively.
[3] All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.