Overview and Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Service Area Square Miles			6,000
Service Area By County			24
Approximate number of retail customers			500,000
Approximate number of DPLER customers			$ 175,000
Number of coal fired power plants			8
Entity number of employees	1,501		1,501
Employees under a collective bargaining agreement which expires in October-2011			52.00%
Capitalized interest for unregulated generation propety	900,000	1,100,000	3,400,000	3,500,000
DP&L [Member]
Service Area Square Miles			6,000
Service Area By County			24
Approximate number of retail customers			500,000
Number of coal fired power plants			8
Entity number of employees	1,443		1,443
Employees under a collective bargaining agreement which expires in October-2011			54.00%
Capitalized interest for unregulated generation propety	$ 900,000	$ 1,100,000	$ 3,400,000	$ 3,500,000