Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended			11 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Nov. 27, 2011 Predecessor [Member]	Dec. 31, 2010 Predecessor [Member]
Balance at beginning of year	$ 24.9	$ 25.0	$ 25.0	$ 19.4	$ 19.4	$ 19.3
Tax positions taken during prior periods		(6.3)	(6.3)	2.0	2.0	(0.4)
Tax positions taken during current period	0.1	(0.4)	(0.4)	3.6
Settlement with taxing authorities, increase					3.5	0.3
Lapse of applicable statute of limitations						0.2
Balance at end of year	$ 25.0	$ 18.3	$ 18.3	$ 25.0	$ 24.9	$ 19.4