Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Estimated annual effective income tax rate			31.00%	33.20%
Tax Refund	$ 19.9		$ 19.9
Decrease in income tax expense			1.2
Increase (decrease) in deferred tax liabilities			41.1
Additional tax decrease			1.2
Effective income tax rates	25.40%	(1.20%)	21.50%	(2.30%)
DP&L [Member]
Estimated annual effective income tax rate			29.50%	30.70%
Increase (decrease) in deferred tax liabilities			$ 28.4
Effective income tax rates	24.40%	(138.30%)	22.50%	40.30%