Fair Value Of Financial Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Auction Rate Securities [Abstract]
Settlements	$ 7	$ (9)
Interest Rate Current [Member]
Auction Rate Securities [Abstract]
Level 3 ARS Assumptions	0.30%
Auction Rate Securities [Member] | Discounted Cash Flow [Member] | Risk Adjusted Discount Rates [Member]
Auction Rate Securities [Abstract]
Level 3 ARS Assumptions	5.00%
Duke Energy Carolinas [Member]
Auction Rate Securities [Abstract]
Settlements	7
Duke Energy Ohio [Member]
Auction Rate Securities [Abstract]
Settlements	(3)
Duke Energy Indiana [Member]
Auction Rate Securities [Abstract]
Settlements		$ (10)