Earnings Per Common Share (EPS) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Average shares, basic	1,332,000,000	1,320,000,000	1,331,000,000	1,315,000,000
Average shares, diluted	1,333,000,000	1,322,000,000	1,332,000,000	1,316,000,000
EPS, basic	$ 0.35	$ 0.51	$ 1.06	$ 0.68
EPS, diluted	$ 0.35	$ 0.51	$ 1.06	$ 0.68
Value of stock options, performance and unvested stock awards not included in the effect of dilutive securities			11,000,000	16,000,000
Proceeds from sale of common stock		$ 98,000,000		$ 205,000,000
Income [Member]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic	471,000,000.00	669,000,000.00	1,415,000,000	891,000,000
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - diluted	$ 471,000,000.00	$ 669,000,000.00	$ 1,415,000,000	$ 891,000,000
Average Shares [Member]
Average shares, basic	1,332,000,000.00	1,320,000,000.00	1,331,000,000	1,315,000,000
Average shares, diluted	1,333,000,000.00		1,332,000,000	1,316,000,000
Average shares, basic and diluted		1,322,000,000.00		1,322,000,000.00
Stock options, performance and restricted stock	1,000,000.00	2,000,000.00	1,000,000	1,000,000
EPS [Member]
EPS, basic	$ 0.35	$ 0.51	$ 1.06	$ 0.68
EPS, diluted	$ 0.35		$ 1.06	$ 0.68
EPS, basic and diluted		$ 0.51