Fair Value (Nonrecurring Measurements) (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2014
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	$ 383,000,000	$ 661,000,000	$ 1,940,000,000
Other non-operating expense	128,000,000	129,000,000	50,000,000
Goodwill impairment expense	164,000,000	372,000,000	1,817,000,000
DP&L (East Bend)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	2,000,000					2,000,000
Ebute
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	36,000,000					36,000,000
Goodwill impairment expense				58,000,000
UK Wind (Newfield)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring								0
DPLER
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense					136,000,000
Buffalo Gap
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense					18,000,000	10,000,000
Itabo (San Lorenzo)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring				7,000,000
DP&L (Conesville)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
DP&L
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense			1,820,000,000				307,000,000
Mountain View
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense							7,000,000
Long Lived Assets Held And Used | DP&L (East Bend)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	12,000,000
Long Lived Assets Held And Used | Ebute
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	67,000,000
Long Lived Assets Held And Used | UK Wind (Newfield)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	11,000,000
Long Lived Assets Held And Used | Itabo (San Lorenzo)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		16,000,000
Long Lived Assets Held And Used | Beaver Valley
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		46,000,000
Long Lived Assets Held And Used | DP&L (Conesville)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		26,000,000
Long Lived Assets Held For Sale | U.S. wind turbines
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		0
Discontinued Operations and Held for Sale Businesses | Cameroon businesses
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	38,000,000	63,000,000
Discontinued Operations and Held for Sale Businesses | Saurashtra
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		12,000,000
Discontinued Operations and Held for Sale Businesses | Ukraine utilities
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		44,000,000
Discontinued Operations and Held for Sale Businesses | Poland wind projects
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		65,000,000
Discontinued Operations and Held for Sale Businesses | U.S. wind projects
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense		47,000,000
Equity Method Affiliate
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other non-operating expense		129,000,000
Equity Method Affiliate | Silver Ridge Power
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other non-operating expense	42,000,000
Equity Method Affiliate | Entek
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other non-operating expense	86,000,000
Goodwill | Ebute
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense		58,000,000
Goodwill | DPLER
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense	136,000,000
Goodwill | Buffalo Gap
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense	28,000,000
Goodwill | DP&L
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense		307,000,000
Goodwill | Mountain View
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Goodwill impairment expense		7,000,000
Carrying Amount | Long Lived Assets Held And Used | DP&L (East Bend)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	14,000,000					14,000,000
Carrying Amount | Long Lived Assets Held And Used | Ebute
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	103,000,000					103,000,000
Carrying Amount | Long Lived Assets Held And Used | UK Wind (Newfield)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	11,000,000					11,000,000
Carrying Amount | Long Lived Assets Held And Used | Itabo (San Lorenzo)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		23,000,000					23,000,000
Carrying Amount | Long Lived Assets Held And Used | Beaver Valley
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		61,000,000					61,000,000
Carrying Amount | Long Lived Assets Held And Used | DP&L (Conesville)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		26,000,000					26,000,000
Carrying Amount | Long Lived Assets Held For Sale | U.S. wind turbines
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		25,000,000					25,000,000
Carrying Amount | Discontinued Operations and Held for Sale Businesses | Cameroon businesses
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	372,000,000	414,000,000				372,000,000	414,000,000
Carrying Amount | Discontinued Operations and Held for Sale Businesses | Saurashtra
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		19,000,000					19,000,000
Carrying Amount | Discontinued Operations and Held for Sale Businesses | Ukraine utilities
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		164,000,000					164,000,000
Carrying Amount | Discontinued Operations and Held for Sale Businesses | Poland wind projects
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		79,000,000					79,000,000
Carrying Amount | Discontinued Operations and Held for Sale Businesses | U.S. wind projects
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		77,000,000					77,000,000
Carrying Amount | Equity Method Affiliate
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		240,000,000					240,000,000
Carrying Amount | Equity Method Affiliate | Silver Ridge Power
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	315,000,000					315,000,000
Carrying Amount | Equity Method Affiliate | Entek
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	211,000,000					211,000,000
Carrying Amount | Goodwill | Ebute
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		58,000,000					58,000,000
Carrying Amount | Goodwill | DPLER
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	136,000,000					136,000,000
Carrying Amount | Goodwill | Buffalo Gap
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	28,000,000					28,000,000
Carrying Amount | Goodwill | DP&L
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		623,000,000					623,000,000
Carrying Amount | Goodwill | Mountain View
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		7,000,000					7,000,000
Fair Value | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	309,000,000					309,000,000
Fair Value | Long Lived Assets Held And Used | DP&L (East Bend) | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	2,000,000					2,000,000
Fair Value | Long Lived Assets Held And Used | Ebute | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Long Lived Assets Held And Used | Ebute | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Long Lived Assets Held And Used | Ebute | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	36,000,000					36,000,000
Fair Value | Long Lived Assets Held And Used | UK Wind (Newfield) | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Long Lived Assets Held And Used | UK Wind (Newfield) | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Long Lived Assets Held And Used | UK Wind (Newfield) | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Long Lived Assets Held And Used | Itabo (San Lorenzo) | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | Itabo (San Lorenzo) | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | Itabo (San Lorenzo) | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		7,000,000					7,000,000
Fair Value | Long Lived Assets Held And Used | Beaver Valley | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | Beaver Valley | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | Beaver Valley | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		15,000,000					15,000,000
Fair Value | Long Lived Assets Held And Used | DP&L (Conesville) | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | DP&L (Conesville) | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held And Used | DP&L (Conesville) | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held For Sale | U.S. wind turbines | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Long Lived Assets Held For Sale | U.S. wind turbines | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		25,000,000					25,000,000
Fair Value | Long Lived Assets Held For Sale | U.S. wind turbines | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Discontinued Operations and Held for Sale Businesses | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Discontinued Operations and Held for Sale Businesses | Cameroon businesses | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0	0				0	0
Fair Value | Discontinued Operations and Held for Sale Businesses | Cameroon businesses | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	334,000,000	351,000,000				334,000,000	351,000,000
Fair Value | Discontinued Operations and Held for Sale Businesses | Cameroon businesses | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Discontinued Operations and Held for Sale Businesses | Saurashtra | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		7,000,000					7,000,000
Fair Value | Discontinued Operations and Held for Sale Businesses | Ukraine utilities | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		120,000,000					120,000,000
Fair Value | Discontinued Operations and Held for Sale Businesses | Poland wind projects | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		14,000,000					14,000,000
Fair Value | Discontinued Operations and Held for Sale Businesses | U.S. wind projects | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		30,000,000					30,000,000
Fair Value | Equity Method Affiliate | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Equity Method Affiliate | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Equity Method Affiliate | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		111,000,000					111,000,000
Fair Value | Equity Method Affiliate | Silver Ridge Power | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	273,000,000					273,000,000
Fair Value | Equity Method Affiliate | Entek | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	125,000,000					125,000,000
Fair Value | Goodwill | DPLER | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | DPLER | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | DPLER | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | Buffalo Gap | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | Buffalo Gap | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | Buffalo Gap | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring	0					0
Fair Value | Goodwill | DP&L | Level 1
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Goodwill | DP&L | Level 2
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		0					0
Fair Value | Goodwill | DP&L | Level 3
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset fair value nonrecurring		$ 316,000,000					$ 316,000,000