Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013 employee	Jun. 30, 2012	Jun. 30, 2013 sqmi employee	Jun. 30, 2012
Service Area Square Miles			6,000
Approximate number of retail customers			513,000
Approximate number of DPLER customers			264,000
Entity number of employees	1,471		1,471
Number of coal fired power plants			8
Employees under a collective bargaining agreement which expires in October-2011			52.00%
Capitalized interest for unregulated generation propety	$ 0.5	$ 1.2	$ 0.8	$ 2.6
DP&L [Member]
Approximate number of retail customers			513,000
Entity number of employees	1,413		1,413
Employees under a collective bargaining agreement which expires in October-2011			54.00%
Capitalized interest for unregulated generation propety	$ 0.5	$ 1.2	$ 0.8	$ 2.6