Business Segments (Business Segment Data) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Unaffiliated Revenues	$ 3,577	$ 3,534	$ 7,207	$ 7,197
Intersegment Revenues	0	0	0	0
Segment Reporting Information, Revenue for Reportable Segment, Total	3,577	3,534	7,207	7,197
Add back Noncontrolling interest component	4	6	8	8
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(1)	0	1	0
Net Income (Loss)	448	441	747	954
Duke Energy Ohio [Member]
Unaffiliated Revenues	717	694	1,629	1,573
Net Income (Loss)	45	33	119	106
U.S. Franchised Electric And Gas [Member]
Unaffiliated Revenues	2,688	2,540	5,348	5,214
Intersegment Revenues	9	9	17	18
Segment Reporting Information, Revenue for Reportable Segment, Total	2,697	2,549	5,365	5,232
Segment Income	337	297	473	638
Commercial Power [Member]
Unaffiliated Revenues	488	592	1,052	1,234
Intersegment Revenues	14	3	30	5
Segment Reporting Information, Revenue for Reportable Segment, Total	502	595	1,082	1,239
Segment Income	28	30	59	79
International Energy [Member]
Unaffiliated Revenues	397	406	799	754
Intersegment Revenues	0	0	0	0
Segment Reporting Information, Revenue for Reportable Segment, Total	397	406	799	754
Segment Income	105	127	247	255
Total Reportable Segments [Member]
Unaffiliated Revenues	3,573	3,538	7,199	7,202
Intersegment Revenues	23	12	47	23
Segment Reporting Information, Revenue for Reportable Segment, Total	3,596	3,550	7,246	7,225
Segment Income	470	454	779	972
Total Reportable Segments [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	729	694	1,656	1,573
Segment Income	47	35	125	111
Other [Member]
Unaffiliated Revenues	4	(4)	8	(5)
Intersegment Revenues	12	13	23	25
Segment Reporting Information, Revenue for Reportable Segment, Total	16	9	31	20
Segment Income	(25)	(19)	(41)	(26)
Other [Member] | Duke Energy Ohio [Member]
Segment Income	(2)	(2)	(6)	(5)
Eliminations [Member]
Intersegment Revenues	(35)	(25)	(70)	(48)
Segment Reporting Information, Revenue for Reportable Segment, Total	(35)	(25)	(70)	(48)
Eliminations [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	(12)		(27)
DEO Commercial Power [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	342	379	796	794
Segment Income	17	6	61	34
Franchised Electric & Gas [Member] | Duke Energy Ohio [Member]
Unaffiliated Revenues	387	315	860	779
Segment Income	$ 30	$ 29	$ 64	$ 77