Common Stock (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Common Stock [Line Items]
Income from continuing operations attributable to Duke Energy common shareholders, as adjusted for participating securities — basic and diluted	$ 888	$ 942	$ 2,356		$ 1,890
Average shares, basic	707	706	707		706
Average shares, diluted	707	706	707		706
EPS, basic (usd per share)	$ 1.25	$ 1.33	$ 3.33		$ 2.67
EPS, diluted (usd per share)	$ 1.25	$ 1.33	$ 3.33		$ 2.67
Common Class A [Member]
Common Stock [Line Items]
Income from continuing operations attributable to Duke Energy common shareholders, as adjusted for participating securities — basic and diluted	$ 887	$ 942	$ 2,351		$ 1,884
Average shares, basic	707	706	707		706
Average shares, diluted	707	706	707		706
EPS, basic (usd per share)	$ 1.25	$ 1.33	$ 3.33		$ 2.67
EPS, diluted (usd per share)	$ 1.25	$ 1.33	$ 3.33		$ 2.67
Number of stock options and performance and unvested stock awards excluded from the dilutive securities calculation			2	[1]	2	[1]
Dividends declared per share (usd per share)	$ 0.795	$ 0.78	$ 2.355		$ 2.31

[1] Stock options and performance and unvested stock awards were not included in the dilutive securities calculation because either the option exercise prices were greater than the average market price of the common shares during those periods, or performance measures related to the awards had not yet been met.