Acquisitions and Sales of Other Assets (Pro Forma Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Significant Acquisitions and Disposals [Line Items]
Revenues	$ 5,724
Net Income Attributable to Duke Energy Corporation	$ 463
Basic Earnings Per Share	$ 0.66
Diluted Earnings Per Share	$ 0.66