Common Stock (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Line Items]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted									$ 2,451	$ 2,574	$ 1,593
Average shares, basic									707	706	574
Average shares, diluted									707	706	575
EPS, basic	$ 0.14	$ 1.25	$ 1.02	$ 1.05	$ 0.96	$ 1.33	$ 0.40	$ 0.93	$ 3.46	$ 3.64	$ 2.77
EPS, diluted	$ 0.14	$ 1.25	$ 1.02	$ 1.05	$ 0.96	$ 1.33	$ 0.40	$ 0.93	$ 3.46	$ 3.63	$ 2.77
Common Class A [Member]
Earnings Per Share [Line Items]
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted									$ 2,446	$ 2,565	$ 1,588
Average shares, basic									707	706	574
Stock options, performance and restricted stock											1
Average shares, diluted									707	706	575
EPS, basic									$ 3.46	$ 3.64	$ 2.77
EPS, diluted									$ 3.46	$ 3.63	$ 2.77
Number of stock options and performance and unvested stock awards excluded from the dilutive securities calculation									2	2	1
Dividends declared per share									$ 3.15	$ 3.09	$ 3.03