Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income taxes receivable		$ 52
Income tax payable	$ 76
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	25	47
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income taxes receivable		29
Income tax payable	41
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income tax payable	19	16
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable	15
Income tax payable		3
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income taxes receivable		8
Income tax payable	1
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 26
Income tax payable		$ 45