Acquisitions and Sales of Other Assets (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended					9 Months Ended			0 Months Ended	6 Months Ended	9 Months Ended					9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Progress Energy [Member]	Sep. 30, 2012 Sumitomo Corporation of America [Member]	Jan. 12, 2012 Wabash Valley Power Association [Member]	Sep. 30, 2012 NCUC and PSCSC [Member]	Sep. 30, 2012 Kentucky Public Service Commission [Member]	Sep. 30, 2012 Duke Energy Corp [Member] Sumitomo Corporation of America [Member]	Jan. 12, 2012 Duke Energy Ohio [Member]	Jun. 30, 2011 Duke Energy Ohio [Member]	Sep. 30, 2012 Duke Energy Ohio [Member]	Sep. 30, 2011 Duke Energy Ohio [Member]	Sep. 30, 2012 Duke Energy Indiana [Member]	Sep. 30, 2011 Duke Energy Indiana [Member]	Jan. 12, 2012 Duke Energy Indiana [Member]	Sep. 30, 2012 Duke Energy Carolinas [Member]	Sep. 30, 2011 Duke Energy Carolinas [Member]
Duke Energy common shares issued for Progress Energy common shares outstanding			257,867
Exchange Ratio Adjusted for Reverse Stock Split	87.083%		87.083%
Settlement agreement, customer guaranteed savings			$ 650,000,000
Interim FERC Mitigation Rate Reduction			65,000,000
Impairment of other long-lived assets			588,000,000	309,000,000								9,000,000	0	88,000,000	580,000,000	222,000,000
Transfer of Other Real Estate													(28,000,000)		26,000,000	0
Proceeds From Sale of Interest In Jointly Owned Utility Plant											82,000,000
Sale of Ownership Interest in Vermillion Generating Station											75.00%
Equity Method Investment, Ownership Percentage						50.00%
Ownership Interest in Vermillion Generation Station							37.50%										62.50%
Construction and 12-year amortizing Term Loan Facility										330,000,000
Proceeds from Issuance of Other Long-term Debt										319,000,000
After Tax Transaction costs	293,000,000	15,000,000	311,000,000	34,000,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual					2,749,000,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual					226,000,000
Community support and charitable contributions expense			$ 100,000,000	$ 0				$ 99,000,000	$ 165,000									$ 59,000,000	$ 0