Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 1	$ 52
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	65	47
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income taxes receivable		29
Income tax payable	11
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable	22
Income tax payable		16
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable	6
Income tax payable		3
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income taxes receivable		8
Income tax payable	7
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income tax payable	$ 7	$ 45