Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Duke Energy Carolinas
Related Party Transaction [Line Items]
Intercompany income tax payable	$ 36	$ 31
Progress Energy
Related Party Transaction [Line Items]
Intercompany income tax receivable	74
Intercompany income tax payable		33
Duke Energy Progress
Related Party Transaction [Line Items]
Intercompany income tax payable	4	46
Duke Energy Florida
Related Party Transaction [Line Items]
Intercompany income tax receivable	1
Intercompany income tax payable		35
Duke Energy Ohio
Related Party Transaction [Line Items]
Intercompany income tax payable	6	2
Duke Energy Indiana
Related Party Transaction [Line Items]
Intercompany income tax receivable		9
Intercompany income tax payable	7
Piedmont
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 22	$ 10