Variable Interest Entities (Schedule of Accounts Receivable Securitizations) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Long-Term Debt		$ 49,030	$ 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		6,604	7,204
Duke Energy Florida [Member]
Variable Interest Entities [Line Items]
Long-Term Debt		$ 6,247	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		$ 634	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		$ 497	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, 2019
Facility size		$ 225
Long-Term Debt		225	225
Accounts Receivable from Securitization		$ 313	$ 317
Subsequent Event [Member] | 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