Debt And Credit Facilities (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended					1 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Apr. 04, 2011	Mar. 31, 2012 Duke Energy Indiana [Member]	Mar. 31, 2012 Cinergy Receivables [Member]	Dec. 31, 2011 Cinergy Receivables [Member]	Nov. 30, 2011 Duke Energy Master Credit Facility expiring in November 2016 [Member]
Principal amount of senior notes				$ 250,000,000
Notes fixed interest rate				4.20%
Demand notes, maximum amount available for sale			1,000,000,000
Equity method investment, ownership percentage sale	25.00%
Investment balance		64,000,000
Investment balance, debt obligations		64,000,000
Non-recourse debt relating to VIEs					275,000,000	273,000,000
Proceeds from sales of notes	126,000,000	79,000,000
Credit facility, outstanding balance							6,000,000,000
Available Capacity							4,000,000,000
Conditional capacity			$ 500,000,000				$ 2,000,000,000