Acquisitions And Sales Of Other Assets (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended	3 Months Ended						3 Months Ended
	Sep. 02, 2011	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Merger Agreement [Member]	Dec. 31, 2011 Merger Agreement [Member]	Mar. 31, 2012 Progress Energy [Member]	Mar. 31, 2012 Duke Energy Corp [Member]	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2012 Minimum [Member]
Conversion of Progress' common stock to Duke's common stock, per share, before reverse stock split adjustment					2.6125
Number of shares to be issued by Duke to acquire Progress, before reverse stock split adjustment		773
Adjusted conversion ratio, after reverse stock split adjustment		0.87083
Number of shares to be issued by Duke to acquire Progress, after reverse stock split adjustment				258
Value of transaction				$ 16,000,000,000
Incremental goodwill as a result of the merger				10,000,000,000
Debt assumed by Duke as a result of the merger				15,000,000,000
Settlement agreement, customer guaranteed savings	650,000,000
Merger agreement, termination fees						400,000,000	675,000,000
Transaction costs		8,000,000	11,000,000
Accruals for commitments from merger								600,000,000	400,000,000
Estimsted upgrade costs		$ 110,000,000