Summary of Significant Accounting Policies (Accounts Payable and Supplier Invoices Sold) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Payables [Line Items]
Outstanding Accounts Payable Balance Sold	$ 19	$ 15
Suppliers Invoices Settled Through The Program	122	45
Progress Energy
Payables [Line Items]
Outstanding Accounts Payable Balance Sold	9
Suppliers Invoices Settled Through The Program	10
Duke Energy Florida
Payables [Line Items]
Outstanding Accounts Payable Balance Sold	9
Suppliers Invoices Settled Through The Program	10
Duke Energy Ohio
Payables [Line Items]
Outstanding Accounts Payable Balance Sold	6	1
Suppliers Invoices Settled Through The Program	12	9
Piedmont
Payables [Line Items]
Outstanding Accounts Payable Balance Sold	4	14
Suppliers Invoices Settled Through The Program	$ 100	$ 36