Fair Value Measurements (Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis) (Details) (USD $)	3 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Carrying Value		$ 2,507,900,000	$ 2,534,200,000
Fixed asset impairment		11,500,000
Goodwill		317,000,000	452,800,000
Goodwill Impairment	135,800,000	135,800,000
Parent Company [Member]
Fixed asset impairment		11,500,000
Goodwill Impairment		135,800,000
DPLER [Member]
Goodwill Impairment		135,800,000
DPLER [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Goodwill Impairment		135,800,000
East Bend Station [Member]
Fixed asset impairment		11,500,000
Fair Value		2,700,000
East Bend Station [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fixed asset impairment		14,200,000
East Bend Station [Member] | Level 3 [Member]
Fixed asset impairment		$ 2,700,000