Fair Value Measurements (Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Mar. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Carrying Value		$ 2,501.4	$ 2,534.2
Fixed asset impairment		11.5
Goodwill		317.0	452.8
Goodwill Impairment	135.8	135.8
Parent Company [Member]
Fixed asset impairment		11.5
Goodwill Impairment		135.8
DPLER [Member]
Goodwill Impairment		135.8
DPLER [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Goodwill Impairment		135.8
East Bend Station [Member]
Fixed asset impairment		11.5
Fair Value		2.7
East Bend Station [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fixed asset impairment		14.2
East Bend Station [Member] | Level 3 [Member]
Fixed asset impairment		$ 2.7