Accumulated Other Comprehensive Loss (Tables)
 3 Months Ended
Mar. 31, 2016
Other Comprehensive Income (Loss), Tax [Abstract]  
Components Of Accumulated Other Comprehensive Loss
Three Months Ended March 31, 2016 (in millions)
Gains and Losses on Cash Flow Hedges(1)
 
Pension and OPEB Items(1)
 
Accumulated
Other
Comprehensive
Loss(1)
Balance as of January 1, 2016
$
(3.9
)
 
$
(0.1
)
 
$
(4.0
)
Other comprehensive income before reclassifications
—

 
—

 
—

Amounts reclassified from accumulated other comprehensive income(2)
0.5

 
—

 
0.5

Net current-period other comprehensive income
0.5

 
—

 
0.5

Allocation of accumulated other comprehensive loss to noncontrolling interest
0.4

 
—

 
0.4

Balance as of March 31, 2016
$
(3.8
)
 
$
(0.1
)
 
$
(3.9
)
(1)Amounts in parentheses indicate debits.
(2)Includes amounts allocated to noncontrolling interest.
Three Months Ended March 31, 2015 (in millions)
Gains and Losses on Cash Flow Hedges(1)
 
Pension and OPEB Items(1)
 
Accumulated
Other
Comprehensive
Loss(1)
Balance as of January 1, 2015
$
(16.6
)
 
$
(0.1
)
 
$
(16.7
)
Predecessor net tax liabilities not assumed by Columbia OpCo(2)
(10.2
)
 
(0.1
)
 
(10.3
)
Other comprehensive income before reclassifications
—

 
—

 
—

Amounts reclassified from accumulated other comprehensive income(3)
0.1

 
—

 
0.1

Net current-period other comprehensive income
0.1

 
—

 
0.1

Allocation of accumulated other comprehensive loss to noncontrolling interest
(22.6
)
 
(0.1
)
 
(22.7
)
Balance as of March 31, 2015
$
(4.1
)
 
$
(0.1
)
 
$
(4.2
)

(1)All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.
(2)Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that will continue to be borne by the Partnership post-IPO.
(3)Includes amounts allocated to noncontrolling interest.