Earnings Per Common Share (EPS) (Details) (USD $) In Millions, except Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Average shares, basic	1,332,000,000	1,314,000,000	1,331,000,000	1,312,000,000
Average shares, diluted	1,333,000,000	1,314,000,000	1,332,000,000	1,313,000,000
EPS, basic	$ 0.33	$ (0.17)	$ 0.71	$ 0.17
EPS, diluted	$ 0.33	$ (0.17)	$ 0.71	$ 0.17
Value of stock options, performance and unvested stock awards not included in the effect of dilutive securities			11,000,000	19,000,000
Proceeds from sale of common stock		$ 77		$ 108
Income [Member]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic	434		944	221
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - diluted	434		944	221
(Loss) income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted		$ (223)
Average Shares [Member]
Average shares, basic	1,332		1,331	1,312
Average shares, diluted	1,333		1,332	1,313
Average shares, basic and diluted		1,314		1,314
Stock options, performance and restricted stock	1		1	1
EPS [Member]
EPS, basic	$ 0.33		$ 0.71	$ 0.17
EPS, diluted	$ 0.33		$ 0.71	$ 0.17
EPS, basic and diluted		$ (0.17)

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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