Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Legal Reserves Details [Line Items]
Reserves for Legal Matters	$ 68	$ 62
Duke Energy Carolinas
Legal Reserves Details [Line Items]
Reserves for Legal Matters	2	2
Progress Energy
Legal Reserves Details [Line Items]
Reserves for Legal Matters	61	55
Duke Energy Progress
Legal Reserves Details [Line Items]
Reserves for Legal Matters	13	12
Duke Energy Florida
Legal Reserves Details [Line Items]
Reserves for Legal Matters	28	22
Piedmont
Legal Reserves Details [Line Items]
Reserves for Legal Matters	$ 1	$ 1