Summary of Significant Accounting Policies (Changes in the Liability for Transmission and Distribution Asset Removal Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Balance at January 1	$ 112.1	$ 112.4
Additions	22.0	10.1
Settlements	(19.2)	(10.4)
Balance at December 31	114.9	112.1
DP&L [Member]
Balance at January 1	112.1	112.4
Additions	22.0	10.1
Settlements	(19.2)	(10.4)
Balance at December 31	$ 114.9	$ 112.1