Schedule I - Condensed Parent Company Financial Statements (Summary Of Debt And Related Terms) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended								12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2011 Parent Company [Member]		Sep. 30, 2011 Parent Company [Member]	Dec. 31, 2010 Parent Company [Member]		Dec. 31, 2011 Unsecured Debt [Member]	Dec. 31, 2010 Unsecured Debt [Member]	Dec. 31, 2011 Unsecured Debt [Member] Parent Company [Member]		Dec. 31, 2011 Commercial Paper [Member] Parent Company [Member]
Debt Instrument [Line Items]
Unsecured debt				$ 3,878	[1]		$ 2,772	[1]	$ 8,961	$ 8,036
Notes payable and commercial paper		450	[2]	604	[3]		450	[3]
Short-term notes payable and commercial paper	(154)			(154)		(75)
Total debt				4,482			3,222
Total long-term debt	18,679	17,935		4,328			3,222
Weighted-Average Rate									5.70%		4.30%	[1]	0.50%	[3]
Year Due, Start				2013					2012
Year Due, End				2021					2037
Intercompany loans	$ 105
Weighted average days to maturity	17	14

[1] As of December 31, 2011, this amount includes an intercompany loan of $105 million with Duke Energy's affiliate, Bison Insurance Company Limited.

[2] 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.

[3] Includes $450 million at December 31, 2011 and 2010 that was classified as Long-term Debt on the Consolidated Balance Sheets due to the existence of long-term credit facilities which back-stop these commercial paper balances, along with Duke Energy's ability and intent to refinance these balances on a long-term basis. The weighted-average days to maturity was 17 days and 14 days as of December 31, 2011 and 2010, respectively.