Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 87	$ 51
Net amounts recognized on the Condensed Consolidated Balance Sheet	87	51
Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	64	35
Gross amounts offset	(4)
Net amounts recognized on the Condensed Consolidated Balance Sheet	60	35
Noncurrent Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	23	16
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet	22	16
Duke Energy Carolinas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	3	2
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	2
Gross amounts offset	(2)
Net amounts recognized on the Condensed Consolidated Balance Sheet	1	2
Progress Energy [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	5	3
Net amounts recognized on the Condensed Consolidated Balance Sheet	5	3
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	4	2
Gross amounts offset	(2)
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	1
Gross amounts offset	(1)
Net amounts recognized on the Condensed Consolidated Balance Sheet		1
Duke Energy Progress [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	4	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	4	2
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	3	1
Gross amounts offset	(2)
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	1
Gross amounts offset	(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	9	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	9	1
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	9	1
Net amounts recognized on the Condensed Consolidated Balance Sheet	9	1
Duke Energy Indiana [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	45	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	45	27
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	45	27
Net amounts recognized on the Condensed Consolidated Balance Sheet	45	27
Piedmont Natural Gas [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	2	2
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	2	2
Net amounts recognized on the Condensed Consolidated Balance Sheet	$ 2	$ 2