Acquisitions and Sales of Other Assets (Pro Forma Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues	$ 6,727	$ 6,700	$ 18,284	$ 18,333
Net Income Attributable to Duke Energy Corporation	$ 889	$ 783	$ 1,876	$ 2,124
Basic Earnings Per Share	$ 1.26	$ 1.12	$ 2.66	$ 3.03
Diluted Earnings Per Share	$ 1.26	$ 1.12	$ 2.66	$ 3.03