Variable Interest Entities (Schedule of Accounts Receivable Securitizations) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Long-Term Debt	$ 50,507	$ 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	7,401	7,204
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt	$ 7,102	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	$ 504	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	$ 795	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	$ 635	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	$ 456	$ 317