Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic			$ 1,344
Average shares, basic	699	444	531	444
Average shares, diluted			531	444
EPS, basic	$ 0.84	$ 1.06	$ 2.50	$ 3.19
EPS, diluted	$ 0.84	$ 1.06	$ 2.50	$ 3.19
Value of stock options, performance and unvested stock awards not included in the effect of dilutive securities			1	4
Income [Member]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted	$ 589	$ 471	$ 1,326	$ 1,415
Average Shares [Member]
Average shares, basic and diluted		444		444
EPS [Member]
EPS, basic and diluted	$ 0.84	$ 1.06	$ 2.50	$ 3.19