Business Segments (Business Segments Data) (Details) (USD $) In Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Jun. 30, 2010	Sep. 30, 2011		Sep. 30, 2010
Unaffiliated Revenues	$ 3,964		$ 3,946			$ 11,161		$ 10,827
Total Revenues	3,964		3,946			11,161		10,827
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	677		967			2,056		1,536
Depreciation and Amortization	455		447			1,346		1,329
Goodwill and other impairment charges	300		44			309		700
Goodwill impairment charge					500
Expense included in 'Other' relating to voluntary severance plan and consolidation of corporate functions			20					164
Duke Energy Indiana [Member]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	(50)		136			163		331
Depreciation and Amortization	100		95			297		281
Goodwill and other impairment charges	222		44			222		44
Duke Energy Indiana [Member] | Edwardsport IGCC Plant [Member]
Goodwill and other impairment charges	222		44
USFE&G [Member]
Unaffiliated Revenues	2,917	[1]	2,934	[1]		8,131	[1]	8,017	[1]
Intersegment Revenues	9	[1]	10	[1]		27	[1]	25	[1]
Total Revenues	2,926	[1]	2,944	[1]		8,158	[1]	8,042	[1]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	721	[1]	946	[1]		2,052	[1]	2,361	[1]
Depreciation and Amortization	352	[1]	350	[1]		1,032	[1]	1,033	[1]
Commercial Power [Member]
Unaffiliated Revenues	684		736			1,918		1,850	[2]
Intersegment Revenues	3		1			8		6	[2]
Total Revenues	687		737			1,926		1,856	[2]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	67		188			217		(287)	[2]
Depreciation and Amortization	56		54			173		167	[2]
Goodwill and other impairment charges					660
Goodwill impairment charge					500	500
Assets impairment charges					160
International Energy [Member]
Unaffiliated Revenues	360		273			1,114		919
Total Revenues	360		273			1,114		919
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	168		110			527		376
Depreciation and Amortization	23		21			66		63
Total Reportable Segments [Member]
Unaffiliated Revenues	3,961		3,943			11,163		10,786
Intersegment Revenues	12		11			35		31
Total Revenues	3,973		3,954			11,198		10,817
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	956		1,244			2,796		2,450
Depreciation and Amortization	431		425			1,271		1,263
Other Adjustments [Member]
Unaffiliated Revenues	3		3	[3]		(2)		41	[3]
Intersegment Revenues	11		14	[3]		36		41	[3]
Total Revenues	14		17	[3]		34		82	[3]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	(74)		(100)	[3]		(176)		(368)	[3]
Depreciation and Amortization	24		22	[3]		75		66	[3]
Eliminations [Member]
Intersegment Revenues	(23)		(25)			(71)		(72)
Total Revenues	(23)		(25)			(71)		(72)
Interest Expense [Member]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	(213)		(202)			(635)		(624)
Interest Income And Other [Member]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	7	[4]	25	[4]		53	[4]	62	[4]
Addition Of Noncontrolling Interest Component Of Reportable Segment And Other EBIT [Member]
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes	$ 1					$ 18		$ 16

[1] As discussed in Note 4, Duke Energy recorded a pre-tax charge of $222 million in the third quarter of 2011 and a $44 million pre-tax charge in the third quarter of 2010 related to the Edwardsport IGCC project.

[2] As discussed in Note 7, in the second quarter of 2010, Commercial Power recorded impairment charges of $660 million, which consisted of a $500 million goodwill impairment charge associated with the non-regulated Midwest generation operations and a $160 million charge to write-down the value of certain non-regulated Midwest generating assets and emission allowances primarily associated with these generation assets.

[3] During the three and nine months ended September 30, 2010, Other recorded a $20 million and $164 million expense, respectively, related to the 2010 voluntary severance plan and the consolidation of certain corporate office functions from the Midwest to Charlotte, North Carolina (See Note 15).

[4] Other within Interest Income and Other includes foreign currency transaction gains and losses and additional noncontrolling interest amounts not allocated to the reportable segments and Other results.