Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 37	$ 51
Net amounts recognized on the Condensed Consolidated Balance Sheet	37	51
Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	15	35
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	13	35
Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	22	16
Net amounts recognized on the Condensed Consolidated Balance Sheet	22	16
Duke Energy Carolinas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Progress Energy [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	3
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	2
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Progress Energy [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Progress [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	1
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Progress [Member] | Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized		1
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Florida [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	1
Duke Energy Indiana [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	7	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	7	27
Piedmont Natural Gas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	1	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 1	$ 2