Acquisitions and Sales of Other Assets (Narrative) (Details) (USD $) Share data in Thousands, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended		8 Months Ended			6 Months Ended			0 Months Ended	6 Months Ended					6 Months Ended
	Jul. 02, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Sep. 02, 2011	Jun. 30, 2012 Sumitomo Corporation of America [Member]	Jan. 12, 2012 Wabash Valley Power Association [Member]	Jun. 30, 2012 NCUC and PSCSC [Member]	Jun. 30, 2012 Kentucky Public Service Commission [Member]	Jun. 30, 2012 Duke Energy Corp [Member] Sumitomo Corporation of America [Member]	Jan. 12, 2012 Duke Energy Ohio [Member]	Jun. 30, 2012 Duke Energy Ohio [Member]	Jun. 30, 2011 Duke Energy Ohio [Member]	Jun. 30, 2012 Duke Energy Indiana [Member]	Jun. 30, 2011 Duke Energy Indiana [Member]	Jan. 12, 2012 Duke Energy Indiana [Member]	Jun. 30, 2012 Maximum [Member]	Jun. 30, 2012 Minimum [Member]
Adjusted conversion ratio, after reverse stock split adjustment	0.87083
Number of shares to be issued by Duke to acquire Progress, after reverse stock split adjustment	257,867
Goodwill	$ 12,287,000,000
Debt assumed by Duke as a result of the merger	15,681,000,000
Settlement agreement, customer guaranteed savings						650,000,000
Interim FERC Mitigation Rate Reduction				65,000,000
Transaction costs		7,000,000	5,000,000	15,000,000	16,000,000
Accruals for commitments from merger																		550,000,000	450,000,000
Estimated upgrade costs				110,000,000
Impairment of other long-lived assets				408,000,000	9,000,000								0	9,000,000	400,000,000	0
Transfer of Other Real Estate													(28,000,000)		26,000,000	0
Proceeds from Divestiture of Interest in Joint Venture												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%
Community support and charitable contributions									100,000,000	165,000
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		$ 12,000,000	$ 4,000,000	$ 18,000,000	$ 20,000,000