Income Taxes (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Effective income tax rates	2.20%	(4.80%)	20.70%	(49.00%)
Estimated annual effective income tax rate			31.20%	(49.00%)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Effective income tax rates	27.90%	30.20%	28.50%	29.90%
Estimated annual effective income tax rate			29.40%	30.40%