Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 employee	Sep. 30, 2012	Sep. 30, 2013 sqmi employee	Sep. 30, 2012
Service Area Square Miles			6,000
Approximate number of retail customers			513,000
Approximate number of DPLER customers			281,000
Entity number of employees	1,436		1,436
Number of coal fired power plants			8
Employees under a collective bargaining agreement which expires in October-2011			53.00%
Capitalized interest for unregulated generation propety	$ 0.4	$ 0.9	$ 1.2	$ 3.4
DP&L [Member]
Approximate number of retail customers			513,000
Entity number of employees	1,376		1,376
Employees under a collective bargaining agreement which expires in October-2011			55.00%
Capitalized interest for unregulated generation propety	$ 0.4	$ 0.9	$ 1.2	$ 3.4