Statements Of Consolidated and Combined Equity and Partners' Capital - USD ($)
$ in Millions
Total
Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss)
Parent [Member]
Common Units [Member]
Limited Partner [Member]
Subordinated Units [Member]
Limited Partner [Member]
Beginning Balance (Predecessor [Member]) at Dec. 31, 2014 $ 4,171.3     $ 4,188.0    
Beginning Balance at Dec. 31, 2014 4,171.3 $ 0.0 $ (16.7)   $ 0.0 $ 0.0
Net Income | Predecessor [Member]       42.7    
Net Income 42.7 0.0 0.0   0.0 0.0
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]       0.0    
Other Comprehensive Income (Loss), Net of Tax 0.1 0.0 0.1   0.0 0.0
Contribution of capital from parent | Predecessor [Member]       1,217.3    
Contribution of capital from parent 1,217.3 0.0 0.0   0.0 0.0
Predecessor net tax liabilities not assumed by Columbia OpCo | Predecessor [Member] [1]       1,232.5    
Predecessor net tax liabilities not assumed by Columbia OpCo [1] 1,222.2 0.0 (10.3)   0.0 0.0
Contributed/Noncontributed Net Parent Investment Adjustments | Predecessor [Member] [2]       (7.7)    
Contributed/Noncontributed Net Parent Investment Adjustments [2] (7.7) 0.0 0.0   0.0 0.0
Distribution to the noncontrolling interest in Columbia OpCo | Predecessor [Member]       0.0    
Distribution to the noncontrolling interest in Columbia OpCo (500.0) (500.0) 0.0   0.0 0.0
Ending Balance (Predecessor [Member]) at Feb. 11, 2015       6,672.8    
Ending Balance at Feb. 11, 2015 6,645.9 0.0 (26.9)   0.0 0.0
Beginning Balance (Predecessor [Member]) at Dec. 31, 2014 4,171.3     4,188.0    
Beginning Balance at Dec. 31, 2014 4,171.3 0.0 (16.7)   0.0 0.0
Net Income 239.0          
Predecessor net tax liabilities not assumed by Columbia OpCo [1],[3]     (10.3)      
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest [3] (22.3)          
Ending Balance (Predecessor [Member]) at Jun. 30, 2015       0.0    
Ending Balance at Jun. 30, 2015 7,503.1 6,255.5 (4.1)   952.7 299.0
Beginning Balance (Predecessor [Member]) at Feb. 11, 2015       6,672.8    
Beginning Balance at Feb. 11, 2015 6,645.9 0.0 (26.9)   0.0 0.0
Net Income | Predecessor [Member]       0.0    
Net Income 196.3 166.7 0.0   16.1 13.5
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]       0.0    
Other Comprehensive Income (Loss), Net of Tax 0.5 0.4 0.1   0.0 0.0
Allocation of Net Investment to Unitholders | Predecessor [Member]       (6,672.8)    
Allocation of Net Investment to Unitholders 0.0 6,185.7 0.0   0.0 487.1
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest | Predecessor [Member]       0.0    
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest 0.0 (22.7) 22.7   0.0 0.0
Net proceeds from IPO | Predecessor [Member]       0.0    
Net proceeds from IPO 1,168.4 0.0 0.0   1,168.4 0.0
Purchase of additional interest in Columbia OpCo | Predecessor [Member] [4]       0.0    
Purchase of additional interest in Columbia OpCo [4] 0.0 424.4 0.0   (227.1) (197.3)
Limited Partners' Capital Account, Distribution Amount | Predecessor [Member]       0.0    
Limited Partners' Capital Account, Distribution Amount (9.2) 0.0 0.0   (4.9) (4.3)
Transfers from parent | Predecessor [Member]       0.0    
Transfers from parent 1.2 1.0 0.0   0.2 0.0
Ending Balance (Predecessor [Member]) at Jun. 30, 2015       $ 0.0    
Ending Balance at Jun. 30, 2015 $ 7,503.1 $ 6,255.5 $ (4.1)   $ 952.7 $ 299.0
[1] Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that continue to be borne by the Partnership post-IPO, as well as associated regulatory assets and liabilities.
[2] Reflects the removal of amounts related to Crossroads Pipeline Company, Columbia Pipeline Group Services Company, Central Kentucky Transmission Company and 1% of the 50% interest in Hardy Storage that were included in the Predecessor but were not contributed to the Partnership, as well as the inclusion of CNS Microwave, which was not part of the Predecessor.
[3] All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.
[4] Represents the purchase of an additional 8.4% limited partner interest in Columbia OpCo, recorded at the historical carrying value of Columbia OpCo’s net assets after giving effect to the $1,168.4 million equity contribution. This decreases common unitholders and subordinated unitholders equity by the same amount it increases noncontrolling interest because the MLP's purchase price for its additional 8.4% interest in Columbia OpCo exceeded book value.