Business Segments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenue, Net	$ 6,821	$ 6,483	$ 17,927	$ 18,137
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(1,054)	(937)	(2,255)	(2,310)
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Revenue, Net	489	462	1,433	1,453
Commercial Portfolio [Member]
Segment Reporting Information [Line Items]
Revenue, Net	140	66	366	214
Commercial Portfolio [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net	140	66	366	214
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	21	(8)	(20)	15
Commercial Portfolio [Member] \| Duke Energy Ohio [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net				14
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent				9
International Energy [Member]
Segment Reporting Information [Line Items]
Revenue, Net	245	281	761	841
International Energy [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net	245	281	761	841
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ (64)	$ (69)	$ (85)	$ (157)
National Methanol Company [Member] \| International Energy [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	25.00%		25.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.13)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
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-Section S99
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-Subparagraph (SX 210.5-03.1)
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