Pension and Postretirement Benefits (Fair Value Measurements of Pension Assets Using Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified										1 Months Ended	11 Months Ended	12 Months Ended			1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2012 Pension [Member]	Dec. 31, 2011 Pension [Member]	Nov. 27, 2011 Pension [Member]	Dec. 31, 2010 Pension [Member]	Dec. 31, 2012 Pension [Member] DP&L [Member]	Dec. 31, 2011 Pension [Member] DP&L [Member]	Dec. 31, 2010 Pension [Member] DP&L [Member]	Dec. 31, 2011 Limited Partnership Interest [Member] Pension [Member]	Nov. 27, 2011 Limited Partnership Interest [Member] Pension [Member]	Dec. 31, 2012 Limited Partnership Interest [Member] Pension [Member]	Dec. 31, 2012 Limited Partnership Interest [Member] Pension [Member] DP&L [Member]	Dec. 31, 2011 Limited Partnership Interest [Member] Pension [Member] DP&L [Member]	Dec. 31, 2011 Common Collective Fund [Member] Pension [Member]	Nov. 27, 2011 Common Collective Fund [Member] Pension [Member]	Dec. 31, 2012 Common Collective Fund [Member] Pension [Member]	Dec. 31, 2012 Common Collective Fund [Member] Pension [Member] DP&L [Member]	Dec. 31, 2011 Common Collective Fund [Member] Pension [Member] DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	$ 361.4	$ 361.4	$ 361.4	$ 335.9	$ 335.8	$ 291.8	$ 361.4	$ 335.9	$ 291.8	$ 0.9	$ 2.8	$ 0.8	$ 0.8	$ 2.8	$ 71.3	$ 57.4	$ 71.4	$ 71.4	$ 57.4
Actual return on plan assets: Relating to assets still held at the reporting date											(0.8)			(0.8)	0.1	(1.5)	1.4	1.4	(1.4)
Actual return on plan assets: Relating to assets sold during the period												0.9	0.9
Purchases, sales, and settlements										(0.1)	(1.1)	(1.7)	(1.7)	(1.2)		15.4	(35.8)	(35.8)	15.4
Fair value of plan assets at December 31	$ 361.4	$ 361.4	$ 361.4	$ 335.9	$ 335.8	$ 291.8	$ 361.4	$ 335.9	$ 291.8	$ 0.8	$ 0.9	$ 0	$ 0	$ 0.8	$ 71.4	$ 71.3	$ 37.0	$ 37.0	$ 71.4