Pension and Postretirement Benefits (Fair Value Measurements of Pension Assets Using Significant Unobservable Inputs) (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 at January 1	$ 349.1
Fair value of plan assets at December 31	349.1
DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	349.1	361.4
Fair value of plan assets at December 31	349.1	361.4
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	349.1	361.4	335.9
Fair value of plan assets at December 31	349.1	361.4	335.9
Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	349.1	361.4	335.9
Fair value of plan assets at December 31	$ 349.1	$ 361.4	$ 335.9