Business Segments (Business Segments Data) (Details) (USD $)	3 Months Ended				12 Months Ended													3 Months Ended	12 Months Ended																																														3 Months Ended		12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2011 Edwardsport IGCC Plant [Member]	Dec. 31, 2011 U.S. Franchised Electric And Gas [Member]		Dec. 31, 2010 U.S. Franchised Electric And Gas [Member]		Dec. 31, 2009 U.S. Franchised Electric And Gas [Member]		Jun. 30, 2010 Commercial Power [Member]	Dec. 31, 2011 Commercial Power [Member]		Dec. 31, 2010 Commercial Power [Member]		Dec. 31, 2009 Commercial Power [Member]		Dec. 31, 2011 International Energy [Member]		Dec. 31, 2010 International Energy [Member]		Dec. 31, 2009 International Energy [Member]		Dec. 31, 2011 Total Reportable Segments [Member]		Dec. 31, 2010 Total Reportable Segments [Member]		Dec. 31, 2009 Total Reportable Segments [Member]		Dec. 31, 2011 Other Adjustments [Member]		Dec. 31, 2010 Other Adjustments [Member]		Dec. 31, 2009 Other Adjustments [Member]		Dec. 31, 2011 Eliminations and Reclassifications [Member]		Dec. 31, 2010 Eliminations and Reclassifications [Member]		Dec. 31, 2009 Eliminations and Reclassifications [Member]		Dec. 31, 2011 Interest Expense [Member]	Dec. 31, 2010 Interest Expense [Member]	Dec. 31, 2009 Interest Expense [Member]	Dec. 31, 2011 Interest Income And Other [Member]		Dec. 31, 2010 Interest Income And Other [Member]		Dec. 31, 2009 Interest Income And Other [Member]		Dec. 31, 2011 Addition Of Noncontrolling Interest Component Of Reportable Segment And Other EBIT [Member]	Dec. 31, 2010 Addition Of Noncontrolling Interest Component Of Reportable Segment And Other EBIT [Member]	Dec. 31, 2009 Addition Of Noncontrolling Interest Component Of Reportable Segment And Other EBIT [Member]	Dec. 31, 2009 Midwest Generation [Member]	Dec. 31, 2011 Duke Energy Indiana [Member]	Dec. 31, 2010 Duke Energy Indiana [Member]	Dec. 31, 2009 Duke Energy Indiana [Member]	Sep. 30, 2011 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Sep. 30, 2010 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]	Dec. 31, 2010 Duke Energy Indiana [Member] Edwardsport IGCC Plant [Member]
Unaffiliated Revenues					$ 14,529,000,000		$ 14,272,000,000		$ 12,731,000,000			$ 10,586,000,000	[1]	$ 10,563,000,000	[1],[2]	$ 9,392,000,000	[2]		$ 2,480,000,000	[3]	$ 2,440,000,000	[3]	$ 2,109,000,000	[3]	$ 1,467,000,000		$ 1,204,000,000		$ 1,158,000,000		$ 14,533,000,000		$ 14,207,000,000		$ 12,659,000,000		$ (4,000,000)		$ 65,000,000	[4],[5]	$ 72,000,000
Intersegment Revenues												33,000,000	[1]	34,000,000	[1],[2]	41,000,000	[2]		11,000,000	[3]	8,000,000	[3]	5,000,000	[3]							44,000,000		42,000,000		46,000,000		48,000,000		53,000,000	[4],[5]	56,000,000		(92,000,000)		(95,000,000)		(102,000,000)
Total Revenues					14,529,000,000		14,272,000,000		12,731,000,000			10,619,000,000	[1]	10,597,000,000	[1],[2]	9,433,000,000	[2]		2,491,000,000	[3]	2,448,000,000	[3]	2,114,000,000	[3]	1,467,000,000		1,204,000,000		1,158,000,000		14,577,000,000		14,249,000,000		12,705,000,000		44,000,000		118,000,000	[4],[5]	128,000,000		(92,000,000)		(95,000,000)		(102,000,000)
Segment EBIT/Consolidated Income (Loss) From Continuing Operations Before Income Taxes					2,465,000,000		2,210,000,000		1,831,000,000			2,604,000,000	[1]	2,966,000,000	[1],[2]	2,321,000,000	[2]		225,000,000	[3]	(229,000,000)	[3]	27,000,000	[3]	679,000,000		486,000,000		365,000,000		3,508,000,000		3,223,000,000		2,713,000,000		(261,000,000)		(255,000,000)	[4],[5]	(251,000,000)								(859,000,000)	(840,000,000)	(751,000,000)	56,000,000	[6]	72,000,000	[6]	102,000,000	[6]	21,000,000	10,000,000	18,000,000		242,000,000	441,000,000	317,000,000
Depreciation and Amortization					1,806,000,000		1,786,000,000		1,656,000,000			1,383,000,000	[1]	1,386,000,000	[1],[2]	1,290,000,000	[2]		230,000,000	[3]	225,000,000	[3]	206,000,000	[3]	90,000,000		86,000,000		81,000,000		1,703,000,000		1,697,000,000		1,577,000,000		103,000,000		89,000,000	[4],[5]	79,000,000																					391,000,000	375,000,000	403,000,000
Capital and Investment Expenditures and Acquisitions					4,464,000,000		4,855,000,000		4,557,000,000			3,717,000,000	[1]	3,891,000,000	[1],[2]	3,560,000,000	[2]		492,000,000	[3]	525,000,000	[3]	688,000,000	[3]	114,000,000		181,000,000		128,000,000		4,323,000,000		4,597,000,000		4,376,000,000		141,000,000		258,000,000	[4],[5]	181,000,000
Segment Assets	62,526,000,000	[7]			62,526,000,000	[7]	59,090,000,000	[7]	57,040,000,000	[7]		47,977,000,000	[1],[7]	45,210,000,000	[1],[2],[7]	42,763,000,000	[2],[7]		6,939,000,000	[3],[7]	6,704,000,000	[3],[7]	7,345,000,000	[3],[7]	4,539,000,000	[7]	4,310,000,000	[7]	4,067,000,000	[7]	59,455,000,000	[7]	56,224,000,000	[7]	54,175,000,000	[7]	2,961,000,000	[7]	2,845,000,000	[4],[5],[7]	2,736,000,000	[7]	110,000,000	[7]	21,000,000	[7]	129,000,000	[7]														10,062,000,000	9,631,000,000
Goodwill and other impairment charges	(59,000,000)		(301,000,000)		335,000,000		726,000,000		420,000,000									660,000,000					42,000,000																																							234,000,000	44,000,000		222,000,000	44,000,000	44,000,000
Goodwill impairment charge				500,000,000			175,000,000		130,000,000									500,000,000	413,000,000				371,000,000																																						371,000,000
Assets impairment charges							44,000,000				222,000,000							42,000,000
Expense included in 'Other' relating to voluntary severance plan and consolidation of corporate functions							172,000,000
Pre-tax charge to write down					160,000,000
Impairment to write down carrying value																			79,000,000
Equity Method Investment, Realized Gain (Loss) on Disposal					$ 11,000,000		$ 103,000,000		$ (21,000,000)

[1] As discussed in Note 4, Duke Energy recorded pre-tax charges of $222 million and $44 million during the years ended December 31, 2011 and 2010, respectively related to the Edwardsport integrated gasification combined cycle (IGCC) plant that is currently under construction.

[2] On December 7, 2009 and January 10, 2010, the North Carolina and South Carolina rate case settlement agreements were approved by the NCUC and PSCSC, respectively. Among other things, the rate case settlements included an annual base rate increase of $315 million in North Carolina to be phased-in primarily over a two-year period beginning January 1, 2010, and a $74 million annual base rate increase in South Carolina effective February 1, 2010. On July 8, 2009, the PUCO approved a $55 million annual increase in rates for electric delivery service. These new rates were effective July 13, 2009. Additionally, on December 29, 2009, the KPSC approved a $13 million increase in annual base natural gas rates. New rates went into effect January 4, 2010.

[3] As discussed further in Note 12, during the year ended December 31, 2011, Commercial Power recorded a $79 million impairment to write-down the carrying value of certain emission allowances. During the year ended December 31, 2010, Commercial Power recorded impairment charges of $660 million, which consisted of a $500 million goodwill impairment charge associated with the non-regulated Midwest generating operations and a $160 million pre-tax charge to write-down the value of certain non-regulated Midwest generating assets and emission allowances primarily associated with these generation assets. During the year ended December 31, 2009, Commercial Power recorded impairment charges of $413 million, which consists of a $371 million goodwill impairment charge associated with the non-regulated Midwest generation operations and a $42 million pre-tax charge to write-down the value of certain generating assets in the Midwest to their estimated fair value.

[4] During 2010, a $172 million expense was recorded related to the 2010 voluntary severance plan and the consolidation of certain corporate office functions from the Midwest to Charlotte, North Carolina (see Note 19).

[5] During 2010, Duke Energy recognized a $139 million pre-tax gain from the sale of a 50% ownership interest in DukeNet (see Note 2), and a $109 million pre-tax gain from the sale of an equity method investment in, Q-Comm Corporation (Q-Comm) (see Note 13).

[6] 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.

[7] Includes assets held for sale and assets of entities in discontinued operations. See Note 13 for description and carrying value of investments accounted for under the equity method of accounting within each segment.