Fair Value Measurements (Fair Value and Redemption Frequency) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Total Fair Value	$ 10.0	$ 11.5
DP&L [Member]
Total Fair Value	10.0	11.5
Equity Securities [Member]
Redemption Frequency	Immediate
Total Fair Value	3.7	4.4
Equity Securities [Member] | DP&L [Member]
Total Fair Value	3.7	4.4
Debt Securities [Member]
Redemption Frequency	Immediate
Total Fair Value	4.9	5.5
Debt Securities [Member] | DP&L [Member]
Total Fair Value	4.9	5.5
Money Market Funds [Member]
Redemption Frequency	Immediate
Total Fair Value	0.1	0.3
Money Market Funds [Member] | DP&L [Member]
Total Fair Value	0.1	0.3
Hedge Funds, Global Opportunity [Member]
Redemption Frequency	Quarterly
Total Fair Value	0.9	0.9
Hedge Funds, Global Opportunity [Member] | DP&L [Member]
Total Fair Value	0.9	0.9
Hedge Funds [Member]
Redemption Frequency	Quarterly
Total Fair Value	0.4	0.4
Hedge Funds [Member] | DP&L [Member]
Total Fair Value	$ 0.4	$ 0.4