Common Stock (Earnings Per Share Data) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities	$ 1,077	$ 954	$ 2,199	$ 2,356
Average shares, basic	713	700	705	700
Equity Forwards, shares	1		1
Average shares, diluted	714	700	706	700
EPS, basic (usd per share)	$ 1.51	$ 1.36	$ 3.12	$ 3.37
EPS, diluted (usd per share)	$ 1.51	$ 1.36	$ 3.11	$ 3.37
Number of stock options and performance and unvested stock awards excluded from the dilutive securities calculation	2	2	2	2
Dividends declared per share (usd per share)	$ 0.9275	$ 0.89	$ 2.7075	$ 2.60