Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated entity - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Duke Energy Carolinas
Related Party Transaction [Line Items]
Intercompany income tax receivable		$ 52
Intercompany income tax payable	$ 5
Progress Energy
Related Party Transaction [Line Items]
Intercompany income tax receivable	125	47
Duke Energy Progress
Related Party Transaction [Line Items]
Intercompany income tax receivable	28	29
Duke Energy Florida
Related Party Transaction [Line Items]
Intercompany income tax payable	2	16
Duke Energy Ohio
Related Party Transaction [Line Items]
Intercompany income tax receivable	9
Intercompany income tax payable		3
Duke Energy Indiana
Related Party Transaction [Line Items]
Intercompany income tax receivable	28	8
Piedmont
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 13
Intercompany income tax payable		$ 45