Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Receivables, allowance for doubtful accounts	$ 37	$ 35
Restricted receivables, allowance for doubtful accounts	42	40
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares outstanding	1,338,000,000	1,336,000,000
Duke Energy Carolinas [Member]
Receivables, allowance for doubtful accounts	3	3
Restricted receivables, allowance for doubtful accounts	6	6
Duke Energy Ohio [Member]
Receivables, allowance for doubtful accounts	16	16
Common stock, par value	$ 8.5	$ 8.5
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares outstanding	89,663,086	89,663,086
Duke Energy Indiana [Member]
Receivables, allowance for doubtful accounts	$ 1	$ 1
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares outstanding	53,913,701	53,913,701