Acquisitions, Dispositions and Sales of Other Assets Acquisitions, Dispositions and Sales of Other Assets (Assets Held For Sale) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax (benefit) expense									$ (295)	$ 29	$ 107
Income (Loss) From Discontinued Operations, net of tax	1	378	(112)	(843)	3	62	50	(29)	(576)	86	171
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Current assets	364								364
Current liabilities	262				7				262	7
Midwest Generation Business [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues									1,748	1,885	1,771
Estimated loss on disposition									(929)
(Loss) Income before income taxes									(818)	141	227
Income tax (benefit) expense									(294)	56	82
Income (Loss) From Discontinued Operations, net of tax									(524)	85	145
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Current assets	364								364
Investments and other assets	52								52
Property, plant and equipment	2,590								2,590
Total assets held for sale	3,006								3,006
Current liabilities	262								262
Deferred credits and other liabilities	35								35
Total liabilities associated with assets held for sale	297								297
Other Disposal Groups [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) From Discontinued Operations, net of tax									(52)	1	26
Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax (benefit) expense									(300)	32	65
Income (Loss) From Discontinued Operations, net of tax	34	413	(135)	(875)	(4)	35	51	(47)	(563)	35	130
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Current assets	316								316
Current liabilities	246								246
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues									1,299	1,503	1,435
Estimated loss on disposition									(959)
(Loss) Income before income taxes									(863)	67	195
Income tax (benefit) expense									(300)	32	65
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Current assets	316								316
Investments and other assets	46								46
Property, plant and equipment	2,559								2,559
Total assets held for sale	2,921								2,921
Current liabilities	246								246
Deferred credits and other liabilities	34								34
Total liabilities associated with assets held for sale	$ 280								$ 280