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Contractual Obligations, Commercial Commitments and Contingencies (Narative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Public Utility, Property, Plant and Equipment [Line Items]    
Due to third parties, current $ 0.5 $ 1.6
Environmental reserves $ 0.9  
Percentage of future committed coal 73.00%  
THE DAYTON POWER AND LIGHT COMPANY [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Environmental reserves $ 0.9  
Percentage of future committed coal 73.00%  
DPLER [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Third party guarantees $ 1.9  
DPLE [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Third party guarantees $ 17.3  
Debt Obligation on 4.9% Equity Ownership [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Equity ownership interest 4.90%  
Equity ownership interest aggregate cost $ 74.5  
Long Term Debt Date Range Equity Ownership, Start 2016  
Long Term Debt Date Range Equity Ownership, End 2040  
Electric Generation Company [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Debt obligation $ 1,519.9