Acquisitions and Sales of Other Assets (Pro Forma Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Significant Acquisitions and Disposals [Line Items]
Revenues	$ 5,858	$ 11,582
Net Income Attributable to Duke Energy Corporation	$ 535	$ 998
Basic Earnings Per Share	$ 0.76	$ 1.42
Diluted Earnings Per Share	$ 0.76	$ 1.42