Fair Value Of Financial Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Auction rate securities sold in period	$ 10	$ 3	$ 73	$ 30
Duke Energy Carolinas [Member]
Auction rate securities sold in period	(2)		6
Duke Energy Ohio [Member]
Auction rate securities sold in period	1	1	(1)	2
Duke Energy Indiana [Member]
Auction rate securities sold in period	16	2	45	14
Auction Rate Securities [Member]
Auction rate securities sold in period			$ (39)
Auction Rate Securities [Member] | Income Approach Valuation Technique [Member] | Risk Adjusted Discount Rates [Member]
Level 3 ARS Assumptions	5.00%		5.00%
Auction Rate Securities [Member] | Income Approach Valuation Technique [Member] | Interest Rate Current [Member]
Level 3 ARS Assumptions	0.50%		0.50%