Income Taxes (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Entity Information [Line Items]
Effective income tax rates	39.20%	28.20%	39.50%	28.80%
Estimated annual effective income tax rate			38.80%	31.20%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Effective income tax rates	36.40%	28.20%	36.90%	28.60%
Estimated annual effective income tax rate			36.70%	29.40%