Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Stock options, performance and restricted stock			0
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - diluted	$ 444
Average shares, basic	446,000,000	444,000,000	446,000,000	444,000,000
Average shares, diluted	446,000,000	444,000,000	446,000,000	444,000,000
EPS, basic	$ 0.99	$ 0.98	$ 1.65	$ 2.13
EPS, diluted	$ 0.99	$ 0.98	$ 1.65	$ 2.13
Value of stock options, performance and unvested stock awards not included in the effect of dilutive securities			4,000,000	2,000,000
Income [Member]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted		434
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic	444		736	944
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - diluted		$ 434	$ 736	$ 944
Average Shares [Member]
Stock options, performance and restricted stock	0	0		0
Average shares, basic	446,000,000	444,000,000	446	444,000,000
Average shares, diluted	446,000,000	444,000,000	446,000,000	444,000,000
EPS [Member]
EPS, basic	$ 0.99	$ 0.98	$ 1.65	$ 2.13
EPS, diluted	$ 0.99	$ 0.98	$ 1.65	$ 2.13