Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Duke Energy Carolinas
Related Party Transaction [Line Items]
Intercompany income tax payable	$ 206	$ 5
Progress Energy
Related Party Transaction [Line Items]
Intercompany income tax receivable		125
Intercompany income tax payable	49
Duke Energy Progress
Related Party Transaction [Line Items]
Intercompany income tax receivable		28
Intercompany income tax payable	104
Duke Energy Florida
Related Party Transaction [Line Items]
Intercompany income tax payable	98	2
Duke Energy Ohio
Related Party Transaction [Line Items]
Intercompany income tax receivable		9
Intercompany income tax payable	6
Duke Energy Indiana
Related Party Transaction [Line Items]
Intercompany income tax receivable		28
Intercompany income tax payable	56
Piedmont Natural Gas
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 14	$ 13