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Overview and Summary of Significant Accounting Policies Overview and Summary of Significant Accounting Polices (Tables)
 12 Months Ended
Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]  
Schedule of Expected Service and Interest Costs
reflect the change in methodology described above. The impact of the change in approach on expected service costs in 2016 is shown below:
$ in millions
 
Expected 2016 Service Cost
 
Expected 2016 Interest Cost
 
 
Disaggregated rate approach
 
Aggregate rate approach
 
Impact of change
 
Disaggregated rate approach
 
Aggregate rate approach
 
Impact of change
Total Pension
 
$
5.7

 
$
6.1

 
$
(0.4
)
 
$
14.8

 
$
17.9

 
$
(3.1
)
Total Postretirement Benefits
 
$
0.2

 
$
0.2

 
$
—

 
$
0.6

 
$
0.7

 
$
(0.1
)
Total
 
$
5.9

 
$
6.3

 
$
(0.4
)
 
$
15.4

 
$
18.6

 
$
(3.2
)
THE DAYTON POWER AND LIGHT COMPANY [Member]  
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]  
Schedule of Expected Service and Interest Costs
reflect the change in methodology described above. The impact of the change in approach on expected service costs in 2016 is shown below:
$ in millions
 
Expected 2016 Service Cost
 
Expected 2016 Interest Cost
 
 
Disaggregated rate approach
 
Aggregate rate approach
 
Impact of change
 
Disaggregated rate approach
 
Aggregate rate approach
 
Impact of change
Total Pension
 
$
5.7

 
$
6.1

 
$
(0.4
)
 
$
14.8

 
$
17.9

 
$
(3.1
)
Total Postretirement Benefits
 
$
0.2

 
$
0.2

 
$
—

 
$
0.6

 
$
0.7

 
$
(0.1
)
Total
 
$
5.9

 
$
6.3

 
$
(0.4
)
 
$
15.4

 
$
18.6

 
$
(3.2
)