Fair Value Of Financial Assets And Liabilities (Additional Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Debt of variable interest entities	$ 915		$ 949
Book Value [Member]
Long-term Debt	20,324	[1]	20,573	[1]
Fair Value [Member]
Long-term Debt, Fair Value	23,028		23,053
Duke Energy Carolinas [Member]
Debt of variable interest entities	300		300
Duke Energy Carolinas [Member] | Book Value [Member]
Long-term Debt	8,522	[2]	9,274	[2]
Duke Energy Carolinas [Member] | Fair Value [Member]
Long-term Debt, Fair Value	9,996		10,629
Duke Energy Ohio [Member] | Book Value [Member]
Long-term Debt	2,551		2,555
Duke Energy Ohio [Member] | Fair Value [Member]
Long-term Debt, Fair Value	2,684		2,688
Duke Energy Indiana [Member] | Book Value [Member]
Long-term Debt	3,707		3,459
Duke Energy Indiana [Member] | Fair Value [Member]
Long-term Debt, Fair Value	$ 4,346		$ 4,048

[1] Includes book value of Non-recourse long-term debt of variable interest entities of $915 million and $949 million June 30, 2012 and December 31, 2011, respectively.

[2] Includes book value of Non-recourse long-term debt of variable interest entities of $300 million at both June 30, 2012 and December 31, 2011, respectively.