Goodwill and Other Intangible Assets (Narrative) (Details)		3 Months Ended			12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2014 USD ($) project	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Feb. 18, 2015
Goodwill [Line Items]
Goodwill impairment expense					$ 317,000,000	$ 164,000,000	$ 372,000,000
Goodwill	$ 1,157,000,000	$ 1,157,000,000	$ 1,458,000,000		1,157,000,000	1,458,000,000	1,622,000,000
Goodwill, Acquired During Period					16,000,000
Goodwill	3,912,000,000	3,912,000,000	3,896,000,000		3,912,000,000	3,896,000,000	$ 3,954,000,000
Buffalo Gap
Goodwill [Line Items]
Goodwill impairment expense			$ 10,000,000	$ 18,000,000
Number of wind projects | project				3
DPLER
Goodwill [Line Items]
Goodwill impairment expense				$ 136,000,000
Goodwill				136,000,000
Goodwill, fair value				$ 0
Main street power [Member]
Goodwill [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired								100.00%
Goodwill, Acquired During Period	16,000,000
Ebute [Member]
Goodwill [Line Items]
Goodwill, Written off Related to Sale of Business Unit						$ 58,000,000
DPL Subsidiary [Member]
Goodwill [Line Items]
Goodwill impairment expense		317,000,000
Goodwill	$ 317,000,000	$ 317,000,000			$ 317,000,000