Variable Interest Entities (Schedule of Accounts Receivable Securitizations) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Long-Term Debt	$ 49,863	$ 49,035
Duke Energy Carolinas [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	9,589	8,598
Duke Energy Progress [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	6,605	7,204
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	$ 7,183	6,327
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Dec. 01, 2020
Facility size	$ 325
Long-Term Debt	325	325
Accounts Receivable from Securitization	$ 498	545
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Dec. 01, 2020
Facility size	$ 450
Long-Term Debt	450	450
Accounts Receivable from Securitization	$ 704	640
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Feb. 01, 2021
Facility size	$ 300
Long-Term Debt	300	300
Accounts Receivable from Securitization	$ 568	459
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Line of Credit Facility, Expiration Date	Apr. 01, 2021
Facility size	$ 225
Long-Term Debt	225	225
Accounts Receivable from Securitization	$ 394	$ 317