Business Segments (Business Segment Data) (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
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues	$ 5,559	$ 6,395	$ 5,708	$ 6,263	$ 5,610	$ 6,217	$ 5,393	$ 5,536	$ 23,925	$ 22,756	$ 17,912
Interest expense									1,622	1,543	1,244
Depreciation and amortization									3,066	2,668	2,145
Equity in earnings (losses) of unconsolidated affiliates									130	122	148
Income tax expense (benefit) from continuing operations									1,669	1,205	623
Segment income									2,451	2,574	1,593
Add back noncontrolling interests component									14	16	18
Income (Loss) From Discontinued Operations, net of tax	1	378	(112)	(843)	3	62	50	(29)	(576)	86	171
Net Income (Loss) Attributable to Parent	97	1,274	609	(97)	688	1,004	339	634	1,883	2,665	1,768
Net income (loss)	100	1,269	613	(93)	692	1,008	342	634	1,889	2,676	1,782
Impairment charges									81	399	666
Deferred foreign taxes									(67)	14	20
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									5,528	5,607	5,958
Assets	120,709				114,779				120,709	114,779	113,856
Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues	480	446	412	575	456	438	408	503	1,913	1,805	1,820
Interest expense									86	74	89
Depreciation and amortization									214	213	195
Income tax expense (benefit) from continuing operations									43	43	33
Segment income									68	67	45
Income (Loss) From Discontinued Operations, net of tax	34	413	(135)	(875)	(4)	35	51	(47)	(563)	35	130
Net Income (Loss) Attributable to Parent									(495)	102	175
Net income (loss)	64	439	(108)	(890)	6	59	58	(21)	(495)	102	175
Impairment charges									94	5	2
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									322	433	514
Assets	9,999				10,763				9,999	10,763	10,560
Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(123)	(135)	(108)
Interest expense									(22)	(6)
Segment income									(10)	(12)	(8)
Segment Reporting Information Assets [Abstract]
Assets	189				188				189	188	170
Intersegment Eliminations [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(1)		(2)
Segment Reporting Information Assets [Abstract]
Assets	(230)				(155)				(230)	(155)	(166)
Other VIEs [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Impairment charges									94
Regulated Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									22,228	20,871	16,042
Equity in earnings (losses) of unconsolidated affiliates									(3)	(1)	(5)
After tax deferral of voluntary severance charge											60
Regulated Utilities [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,894	1,765	1,745
Regulated Utilities [Member] | Operating Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									22,271	20,910	16,080
Interest expense									1,093	986	806
Depreciation and amortization									2,759	2,323	1,827
Equity in earnings (losses) of unconsolidated affiliates										(1)	(5)
Income tax expense (benefit) from continuing operations									1,628	1,522	942
Segment income									2,795	2,504	1,744
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									4,744	5,049	4,220
Assets	106,657				99,884				106,657	99,884	98,162
Regulated Utilities [Member] | Operating Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,895	1,765	1,746
Interest expense									81	74	61
Depreciation and amortization									211	200	179
Income tax expense (benefit) from continuing operations									117	91	91
Segment income									202	151	159
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									300	375	427
Assets	6,908				6,649				6,908	6,649	6,434
Regulated Utilities [Member] | Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(43)	(39)	(38)
Regulated Utilities [Member] | Intersegment Eliminations [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(1)		(1)
International Energy [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,417	1,546	1,549
Equity in earnings (losses) of unconsolidated affiliates									120	110	134
Deferred foreign taxes									373
International Energy [Member] | Operating Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,417	1,546	1,549
Interest expense									93	86	77
Depreciation and amortization									97	100	99
Equity in earnings (losses) of unconsolidated affiliates										110	134
Income tax expense (benefit) from continuing operations									449	166	149
Segment income									55	408	439
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									67	67	551
Assets	5,132				4,998				5,132	4,998	5,406
Commercial Power [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									255	254	299
Equity in earnings (losses) of unconsolidated affiliates									10	7	14
Commercial Power [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									19	40	75
Commercial Power [Member] | Operating Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									255	260	307
Interest expense									58	61	63
Depreciation and amortization									92	110	85
Equity in earnings (losses) of unconsolidated affiliates										7	14
Income tax expense (benefit) from continuing operations									(171)	(148)	(82)
Segment income									(55)	(88)	(59)
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									555	268	1,038
Assets	6,278				6,955				6,278	6,955	6,992
Commercial Power [Member] | Operating Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									19	40	76
Interest expense									5		28
Depreciation and amortization									2	13	16
Income tax expense (benefit) from continuing operations									(67)	(36)	(40)
Segment income									(121)	(65)	(80)
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									22	58	87
Assets	3,187				4,170				3,187	4,170	4,175
Commercial Power [Member] | Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues										(6)	(8)
Commercial Power [Member] | Intersegment Eliminations [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues											(1)
Commercial Power [Member] | Other VIEs [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Impairment charges									94
Total Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									23,900	22,671	17,890
Segment income									2,795	2,824	2,124
Total Reportable Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,913	1,805	1,820
Total Reportable Segments [Member] | Operating Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									23,943	22,716	17,936
Interest expense									1,244	1,133	946
Depreciation and amortization									2,948	2,533	2,011
Equity in earnings (losses) of unconsolidated affiliates									127	116	143
Income tax expense (benefit) from continuing operations									1,906	1,540	1,009
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									5,366	5,384	5,809
Assets	118,067				111,837				118,067	111,837	110,560
Total Reportable Segments [Member] | Operating Segments [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									1,914	1,805	1,822
Interest expense									86	74	89
Depreciation and amortization									213	213	195
Income tax expense (benefit) from continuing operations									50	55	51
Segment income									81	86	79
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									322	433	514
Assets	10,095				10,819				10,095	10,819	10,609
Total Reportable Segments [Member] | Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(43)	(45)	(46)
Total Reportable Segments [Member] | Intersegment Eliminations [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(1)		(2)
Other Segment [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									25	85	22
Other Segment [Member] | Intersegment Eliminations [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									(80)	(90)	(62)
Other Segment [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues									105	175	84
Interest expense									400	416	298
Depreciation and amortization									118	135	134
Equity in earnings (losses) of unconsolidated affiliates										6	5
Income tax expense (benefit) from continuing operations									(237)	(335)	(386)
Segment income									(334)	(238)	(523)
Segment Reporting Information Assets [Abstract]
Capital investments, expenditures and acquisitions									162	223	149
Assets	2,453				2,754				2,453	2,754	3,126
Other Segment [Member] | Corporate, Non-Segment [Member] | Duke Energy Ohio [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Depreciation and amortization									1
Income tax expense (benefit) from continuing operations									(7)	(12)	(18)
Segment income									(13)	(19)	(34)
Segment Reporting Information Assets [Abstract]
Assets	$ 134				$ 99				$ 134	$ 99	$ 117