Summary of Significant Accounting Policies (Summary of Property, Plant, and Equipment) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2011	Nov. 27, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service			$ 2,677.0	$ 2,590.4
Total property, plant and equipment in service, Composite Rate			5.80%	4.80%	5.80%
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest	0.5	3.9	1.5	4.0
DP&L [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service			5,105.3	5,249.0
Total property, plant and equipment in service, Composite Rate			4.40%	4.20%	2.60%
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest			1.5	4.0	4.4
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission			213.1	208.9
Distribution			970.1	935.0
General			56.8	50.6
Non-depreciable			60.8	60.0
Total property, plant and equipment in service			1,300.8	1,254.5
Transmission, Composite Rate			4.10%	4.40%
Distribution, Composite Rate			5.60%	5.40%
General, Composite Rate			12.10%	10.80%
Regulated Operation [Member] | DP&L [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission			388.3	380.9
Distribution			1,528.2	1,480.7
General			111.1	100.0
Non-depreciable			60.8	60.1
Total property, plant and equipment in service			2,088.4	2,021.7
Transmission, Composite Rate			2.30%	2.40%
Distribution, Composite Rate			3.50%	3.40%
General, Composite Rate			6.20%	5.40%
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production / Generation			1,340.8	1,299.7
Other			15.7	16.6
Non-depreciable			19.7	19.6
Total property, plant and equipment in service			1,376.2	1,335.9
Production/Generation, Composite Rate			6.20%	4.40%
Other, Composite Rate			8.90%	11.60%
Unregulated Operation [Member] | DP&L [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production / Generation			3,002.1	3,210.8
Non-depreciable			14.8	16.5
Total property, plant and equipment in service			$ 3,016.9	$ 3,227.3
Production/Generation, Composite Rate			5.20%	4.90%