Pension and Postretirement Benefits (Net Periodic Benefit Cost (Income)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	11 Months Ended	12 Months Ended		1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Pension [Member]	Nov. 27, 2011 Pension [Member]	Dec. 31, 2013 Pension [Member]	Dec. 31, 2012 Pension [Member]	Dec. 31, 2011 Postretirement [Member]	Nov. 27, 2011 Postretirement [Member]	Dec. 31, 2013 Postretirement [Member]	Dec. 31, 2012 Postretirement [Member]	Dec. 31, 2013 DP&L [Member]	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Dec. 31, 2013 DP&L [Member] Pension [Member]	Dec. 31, 2012 DP&L [Member] Pension [Member]	Dec. 31, 2011 DP&L [Member] Pension [Member]	Dec. 31, 2013 DP&L [Member] Postretirement [Member]	Dec. 31, 2012 DP&L [Member] Postretirement [Member]	Dec. 31, 2011 DP&L [Member] Postretirement [Member]
Service cost				$ 0.5	$ 4.5	$ 7.2	$ 6.2		$ 0.1	$ 0.2	$ 0.1				$ 7.2	$ 6.2	$ 5.0	$ 0.2	$ 0.1	$ 0.1
Interest cost				1.5	15.5	15.6	17.3	0.1	0.9	0.8	0.9				15.6	17.3	17.0	0.8	0.9	1.0
Expected return on assets				(2.0)	(22.5)	(23.3)	(22.7)		(0.3)	(0.1)	(0.3)				(23.6)	(22.7)	(24.5)	(0.2)	(0.3)	(0.3)
Actuarial (gain) / loss				0.4	7.6	4.9	5.0		(1.0)	(0.5)	(0.6)				9.3	8.8	8.0	(0.7)	(0.9)	(1.1)
Prior service cost				0.1	2.0	1.5	1.5	(0.1)	0.1						2.8	2.8	2.1	0.1	0.1	0.1
Net Periodic benefit cost / (income) before adjustments				0.5	7.1	5.9	7.3		(0.2)	0.4	0.1				11.3	12.4	7.6	0.2	(0.1)	(0.2)
Settlement Cost																0.6
Net periodic benefit cost / (income)															11.3	13.0	7.6
Period in which the difference between market related value of assets is calculated in years, max	five	five
Period in which the difference between actual and estimated asset returns in MRVA is calculated	three
Market related value of assets	$ 359.8	$ 346.0	$ 335.0									$ 351.2	$ 346.0	$ 335.0