Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Operating revenues	$ 3,368	$ 3,964	$ 3,534	$ 3,663	$ 3,445		$ 3,946		$ 3,287		$ 3,594		$ 14,529	$ 14,272
Operating income (loss)	517	767	679	814	681		1,033		(14)		761		2,777	2,461		2,249
Net income (loss) attributable to Duke Energy Corporation	288	472	435	511	427		670		(222)		445		1,706	1,320		1,075
Basic	$ 0.22	$ 0.35	$ 0.33	$ 0.38	$ 0.32	[1]	$ 0.51	[1]	$ (0.17)	[1]	$ 0.34	[1]	$ 1.28	$ 1.00	[1]	$ 0.83
Diluted	$ 0.22	$ 0.35	$ 0.33	$ 0.38	$ 0.32	[1]	$ 0.51	[1]	$ (0.17)	[1]	$ 0.34	[1]	$ 1.28	$ 1.00	[1]	$ 0.83
Duke Energy Carolinas [Member]
Operating income (loss)													1,480	1,445		1,287
Duke Energy Ohio [Member]
Operating income (loss)													375	(225)		(134)
Duke Energy Indiana [Member]
Operating income (loss)													$ 282	$ 506		$ 423

[1] Quarterly EPS amounts are meant to be stand-alone calculations and are not always additive to full-year amount due to rounding.