Fair Value Of Financial Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Auction rate securities sold in period	$ 54	$ 28	$ 63	$ 27
Duke Energy Carolinas [Member]
Auction rate securities sold in period	8		8
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	5.30%		5.30%
Auction Rate Securities [Member] | Income Approach Valuation Technique [Member] | Interest Rate Current [Member]
Level 3 ARS Assumptions	0.50%		0.50%