Acquisitions And Sales Of Other Assets (Details) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended
	Sep. 02, 2011	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2011
Number of shares to be issued by Duke to acquire Progress, before reverse stock split adjustment				771
Adjusted conversion ratio, after reverse stock split adjustment				0.87083
Settlement agreement, customer guaranteed savings	$ 650,000,000
Transaction costs		13,000,000		29,000,000
Impairment			9,000,000
Duke Energy Corp [Member]
Merger agreement, termination fees		675,000,000		675,000,000
Merger Agreement [Member]
Conversion of Progress' common stock to Duke's common stock, per share, before reverse stock split adjustment		2.6125		2.6125
Number of shares to be issued by Duke to acquire Progress, after reverse stock split adjustment				257
Value of transaction		15,400,000,000		15,400,000,000
Incremental goodwill as a result of the merger		9,300,000,000		9,300,000,000
Debt assumed by Duke as a result of the merger		15,100,000,000		15,100,000,000
Progress Energy [Member]
Merger agreement, termination fees		$ 400,000,000		$ 400,000,000