Business Segments (Business Segment Data) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2011	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Unaffiliated Revenues	$ 6,722	$ 3,964			$ 13,929	$ 11,161
Intersegment Revenues	0	0
Segment Reporting Information, Revenue for Reportable Segment, Total	6,722	3,964			13,929	11,161
Add back Noncontrolling interest component	4	(2)			12	6
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	4	1			5	1
Net Income (Loss)	598	470			1,345	1,424
Duke Energy Ohio [Member]
Unaffiliated Revenues	757	838			2,386	2,411
Net Income (Loss)	14	51	51	157	133	157
U.S. Franchised Electric And Gas [Member]
Unaffiliated Revenues	5,830	2,917			11,178	8,131
Intersegment Revenues	12	9			29	27
Segment Reporting Information, Revenue for Reportable Segment, Total	5,842	2,926			11,207	8,158
Segment Income	790	337			1,263	975
Commercial Power [Member]
Unaffiliated Revenues	508	684			1,560	1,918
Intersegment Revenues	17	3			47	8
Segment Reporting Information, Revenue for Reportable Segment, Total	525	687			1,607	1,926
Segment Income	12	24			71	103
International Energy [Member]
Unaffiliated Revenues	382	360			1,181	1,114
Intersegment Revenues	0	0			0	0
Segment Reporting Information, Revenue for Reportable Segment, Total	382	360			1,181	1,114
Segment Income	103	115			350	370
Total Reportable Segments [Member]
Unaffiliated Revenues	6,720	3,961			13,919	11,163
Intersegment Revenues	29	12			76	35
Segment Reporting Information, Revenue for Reportable Segment, Total	6,749	3,973			13,995	11,198
Segment Income	905	476			1,684	1,448
Total Reportable Segments [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	772	838			2,428	2,411
Segment Income	32		54	165	157
Other [Member]
Unaffiliated Revenues	2	3			10	(2)
Intersegment Revenues	18	11			41	36
Segment Reporting Information, Revenue for Reportable Segment, Total	20	14			51	34
Segment Income	(315)	(5)			(356)	(31)
Other [Member] | Duke Energy Ohio [Member]
Segment Income	(18)		(3)	(8)	(24)
Eliminations [Member]
Intersegment Revenues	(47)	(23)			(117)	(71)
Segment Reporting Information, Revenue for Reportable Segment, Total	(47)	(23)			(117)	(71)
Eliminations [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	(15)				(42)
DEO Commercial Power [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	341	505			1,137	1,299
Segment Income	(17)		16	50	44
Franchised Electric & Gas [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	431	333			1,291	1,112
Segment Income	$ 49		$ 38	$ 115	$ 113