Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		$ 44
Income taxes receivable, current	$ 52
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable, current	47	168
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		21
Income taxes receivable, current	29
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	16
Income taxes receivable, current		44
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	3
Income taxes receivable, current		22
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current		35
Income taxes receivable, current	8
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Accrued Income Taxes, Current	$ 45
Income taxes receivable, current		$ 7