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, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues	$ 5,843	$ 5,789	$ 11,557	$ 11,613
Net Income Attributable to Duke Energy Corporation	$ 527	$ 621	$ 984	$ 1,338
Basic Earnings Per Share	$ 0.75	$ 0.89	$ 1.40	$ 1.91
Diluted Earnings Per Share	$ 0.75	$ 0.89	$ 1.40	$ 1.91