Business Segments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Net Income (Loss)	$ 437	$ 598	$ 448	$ 299	$ 290	$ 470	$ 441	$ 513	$ 1,782	$ 1,714	$ 1,323
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	130	258	211	266	125	311	193	205	865	834	838
Progress Energy [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	34	157	64	152	(74)	293	178	185	407	582	863
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	42	14	45	74	37	51	33	73	175	194	(441)
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	59	(19)	77	(167)	55	(31)	68	76	(50)	168	285
All Other Segments [Member]
Segment Reporting Information [Line Items]
After-tax costs to achieve the merger									397	51
Costs to achieve the merger, tax									239	17
After-tax voluntary severance program expense											105
Voluntary severance program expense, tax											67
All Other Segments [Member] | Progress Energy [Member]
Segment Reporting Information [Line Items]
After-tax costs to achieve the merger									198	33
Costs to achieve the merger, tax									127	22
U.S. Franchised Electric And Gas [Member]
Segment Reporting Information [Line Items]
After-tax deferral of voluntary severance program expense									60
Deferral of voluntary severance program expense, tax									39
Franchised Electric [Member] | Progress Energy [Member]
Segment Reporting Information [Line Items]
After-tax replacement power refund									60
Replacement power refund, tax									40
After-tax refund to customers recorded as reduction to revenue										173
Refund to customers recorded as reduction to revenue, tax										115
North Carolina Rate Case [Member]
Segment Reporting Information [Line Items]
Approved rate increase amount by state commission									309
South Carolina Rate Case [Member]
Segment Reporting Information [Line Items]
Approved rate increase amount by state commission									93
International Energy Interest In National Methanol [Member]
Segment Reporting Information [Line Items]
Equity ownership interest rate	25.00%								25.00%
Duke Energy Interest In Detm [Member]
Segment Reporting Information [Line Items]
Equity ownership interest rate	60.00%								60.00%
Edwardsport Igcc Plant [Member] | U.S. Franchised Electric And Gas [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge									402	135
Impairment charge, tax									226	87
Emission Allowance [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge										51
Impairment charge, tax										28
Emission Allowance [Member] | DEO Commercial Power [Member] | Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge										51
Impairment charge, tax										28
Dukenet [Member]
Segment Reporting Information [Line Items]
Equity ownership interest rate	50.00%								50.00%
Dukenet [Member] | All Other Segments [Member]
Segment Reporting Information [Line Items]
After-tax gain on sale of equity investment											86
Gain on sale of equity investment, tax											53
Q Comm Corporation [Member] | All Other Segments [Member]
Segment Reporting Information [Line Items]
After-tax gain on sale of equity investment											68
Gain on sale of equity investment, tax											41
Commercial Power Non Regulated Midwest Generation [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge											500
Commercial Power Non Regulated Midwest Generation [Member] | DEO Commercial Power [Member] | Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge											461
Crystal River Unit 3 Retirement [Member] | Franchised Electric [Member] | Progress Energy [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge									88
Impairment charge, tax									58
Midwest Generation Asset And Emission Allowance [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge											102
Impairment charge, tax											58
Midwest Generation Asset And Emission Allowance [Member] | DEO Commercial Power [Member] | Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge											102
Impairment charge, tax											58
Ohio Transmission And Distribution Reporting Unit [Member] | Franchised Electric & Gas [Member] | Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
After-tax impairment charge											$ 216