Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Duke Energy Carolinas
Related Party Transaction [Line Items]
Intercompany income tax payable	$ 31	$ 31
Progress Energy
Related Party Transaction [Line Items]
Intercompany income tax receivable	84
Intercompany income tax payable		33
Duke Energy Progress
Related Party Transaction [Line Items]
Intercompany income tax payable	12	46
Duke Energy Florida
Related Party Transaction [Line Items]
Intercompany income tax receivable	46
Intercompany income tax payable		35
Duke Energy Ohio
Related Party Transaction [Line Items]
Intercompany income tax payable	2	2
Duke Energy Indiana
Related Party Transaction [Line Items]
Intercompany income tax receivable		9
Intercompany income tax payable	36
Piedmont
Related Party Transaction [Line Items]
Intercompany income tax receivable		$ 10
Intercompany income tax payable	$ 39