Income Taxes (Narrative) (Details)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Entity Information [Line Items]
Effective income tax rates	21.40%	29.10%
Estimated annual effective income tax rate	20.60%	31.10%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Effective income tax rates	26.90%
Estimated annual effective income tax rate	27.00%	29.40%