Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income taxes receivable		$ 52
Income tax payable	$ 71
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	178	47
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income taxes receivable	60	29
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable	10
Income tax payable		16
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable	14
Income tax payable		3
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income taxes receivable	3	8
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 85
Income tax payable		$ 45