Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 62	$ 65
Duke Energy Carolinas
Legal Reserves Details [Line Items]
Reserves for legal matters	2	9
Progress Energy
Legal Reserves Details [Line Items]
Reserves for legal matters	55	54
Duke Energy Progress
Legal Reserves Details [Line Items]
Reserves for legal matters	12	12
Duke Energy Florida
Legal Reserves Details [Line Items]
Reserves for legal matters	22	24
Piedmont
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 1	$ 1