Pension and Postretirement Benefits (Fair Value Measurements for Postretirement Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 349.1
DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	349.1	361.4
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	4.2	4.5
Postretirement [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	4.2	4.5
JP Morgan Core Bond Fund [Member] | Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	4.2
JP Morgan Core Bond Fund [Member] | Postretirement [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	4.2
Level 1 [Member] | JP Morgan Core Bond Fund [Member] | Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	4.2
Level 1 [Member] | JP Morgan Core Bond Fund [Member] | Postretirement [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3.7	$ 4.2