Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated entity - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Duke Energy Carolinas
Related Party Transaction [Line Items]
Intercompany income tax payable	$ 31	$ 5
Progress Energy
Related Party Transaction [Line Items]
Intercompany income tax receivable		125
Intercompany income tax payable	33
Duke Energy Progress
Related Party Transaction [Line Items]
Intercompany income tax receivable		28
Intercompany income tax payable	46
Duke Energy Florida
Related Party Transaction [Line Items]
Intercompany income tax payable	35	2
Duke Energy Ohio
Related Party Transaction [Line Items]
Intercompany income tax receivable		9
Intercompany income tax payable	2
Duke Energy Indiana
Related Party Transaction [Line Items]
Intercompany income tax receivable	9	28
Piedmont
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 10	$ 13