Income Taxes (Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Effective income tax rates	34.00%	32.90%	35.30%	33.40%
DP&L [Member]
Effective income tax rates	33.60%	32.30%	33.80%	33.10%