Common Stock (Earnings Per Share Data)(Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Income from continuing operations attributable to Duke Energy common stockholders excluding impact of participating securities	$ 504	$ 687	$ 1,123	$ 1,402
Average shares, basic	703	700	702	700
Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements	1
Average shares, diluted	704	700	702	700
EPS, basic (usd per share)	$ 0.72	$ 0.98	$ 1.60	$ 2.00
EPS, diluted (usd per share)	$ 0.72	$ 0.98	$ 1.60	$ 2.00
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)	$ 0.89	$ 0.855	$ 1.78	$ 1.71