Debt And Credit Facilities (Schedule Of Line Of Credit Facilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Sep. 30, 2011	Dec. 31, 2011		Dec. 31, 2010
Notes Payable and Commercial Paper				$ (450)	[1]
Tax-Exempt Bonds		(491)	[2],[3],[4],[5]	(632)	[2],[6],[7],[8]
Commercial Paper		450	[1]
Commercial Paper Issued During The Period	(75)
Maximum [Member]
Debt to total capitalization ratio, for each borrower	65
Master Credit Facility [Member]
Facility Size		4,000	[9]
Notes Payable and Commercial Paper		(525)	[10]
Outstanding Letters of Credit		(85)
Tax-Exempt Bonds		(260)
Available Capacity		3,130
Master Credit Facility [Member] | Duke Energy Corp [Member]
Facility Size		1,250	[9]
Notes Payable and Commercial Paper		(75)	[10]
Outstanding Letters of Credit		(51)
Available Capacity		$ 1,124

[1] Duke Energy has issued $450 million in Commercial Paper, which is backstopped by the master credit facility, and the proceeds are in the form of loans through the money pool to Duke Energy Carolinas of $300 million and Duke Energy Indiana of $150 million as of December 31, 2011.

[2] For Duke Energy Carolinas, the master credit facility served as a backstop for the $95 million of tax-exempt bonds outstanding at December 31, 2011.

[3] Of the $491 million of tax-exempt bonds outstanding at December 31, 2011 at Duke Energy, the master credit facility served as a backstop for $287 million of these tax-exempt bonds (of which $27 million is in the form of letters of credit), with the remaining balance backstopped by other specific long-term credit facilities separate from the master credit facility.

[4] All of the $111 million of tax-exempt bonds outstanding at December 31, 2011 at Duke Energy Ohio were backstopped by Duke Energy's master credit facility (of which $27 million is in the form of letters of credit).

[5] Of the $285 million of tax-exempt bonds outstanding at December 31, 2011 at Duke Energy Indiana, $81 million were backstopped by Duke Energy's master credit facility, with the remaining balance backstopped by other specific long-term credit facilities separate from the master credit facility.

[6] Of the $632 million of tax-exempt bonds outstanding at December 31, 2010, at Duke Energy, the master credit facility served as a backstop for $311 million of these tax-exempt bonds (of which $27 million is in the form of letters of credit), with the remaining balance backstopped by other specific long-term credit facilities separate from the master credit facility.

[7] Of the $161 million of tax-exempt bonds outstanding at December 31, 2010 at Duke Energy Ohio, $111 million were backstopped by Duke Energy's master credit facility (of which $27 million is in the form of letters of credit), with the remaining balance backstopped by other specific long-term credit facilities separate from the master credit facility.

[8] Of the $352 million of tax-exempt bonds outstanding at December 31, 2010 at Duke Energy Indiana, $81 million were backstopped by Duke Energy's master credit facility, with the remaining balance backstopped by other specific long-term credit facilities separate from the master credit facility.

[9] Represents the sublimit of each borrower at December 31, 2011. The Duke Energy Ohio sublimit includes $100 million for Duke Energy Kentucky.

[10] Duke Energy issued $450 million of Commercial Paper and loaned the proceeds through the money pool to Duke Energy Carolinas and Duke Energy Indiana (see money pool table above). The balances are classified as long-term borrowings within Long-term Debt in Duke Energy Carolinas' and Duke Energy Indiana's Consolidated Balance Sheets. Duke Energy issued an additional $75 million of Commercial Paper in 2011. The balance is classified as Notes payable and commercial paper on Duke Energy's Consolidated Balance Sheets.