Derivative Instruments and Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Nov. 27, 2011
Fair Value Frozen			$ 38.9
Derivative Liability, Fair Value, Gross Asset	10.6
Liability position offset by the asset position of counterparties with master netting agreements	5.6
Collateral Already Posted, Aggregate Fair Value	4.7
Collateral if debt were to fall below investment grade	0.3
Derivative Asset, Current	5.4	2.7
Derivative Asset, Noncurrent	8.0	3.6
DP&L [Member]
Derivative Liability, Fair Value, Gross Asset	10.6
Liability position offset by the asset position of counterparties with master netting agreements	4.7
Collateral Already Posted, Aggregate Fair Value	5.6
Collateral if debt were to fall below investment grade	0.3
Short-term Derivative Positions [Member]
Amount No Longer Considered Derivative	0.9	7.2
Long-term Derivative Positions [Member]
Amount No Longer Considered Derivative	$ 0.1	$ 1.0