Income Taxes (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Entity Information [Line Items]
Effective income tax rates	45.70%	(34.10%)	38.60%	24.60%
Estimated annual effective income tax rate			38.60%	30.80%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Effective income tax rates	39.60%	4.90%	36.70%	24.80%
Estimated annual effective income tax rate			36.70%	29.00%