Variable Interest Entities (Schedule of Accounts Receivable Securitizations)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Long-Term debt	$ 49,035	$ 45,576
Duke Energy Carolinas [Member]
Variable Interest Entity [Line Items]
Long-Term debt	8,598	9,187
Duke Energy Progress [Member]
Variable Interest Entity [Line Items]
Long-Term debt	7,204	6,409
Duke Energy Florida [Member]
Variable Interest Entity [Line Items]
Long-Term debt	$ 6,327	5,799
Cinergy Receivables [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Dec. 01, 2020
Facility Size	$ 325
Long-Term debt	$ 325	325
DERF [Member] | Duke Energy Carolinas [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Dec. 01, 2020
Facility Size	$ 450
Long-Term debt	$ 450	425
DEPR [Member] | Duke Energy Progress [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Feb. 01, 2019
Facility Size	$ 300
Long-Term debt	$ 300	300
DEFR [Member] | Duke Energy Florida [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Line of credit facility, expiration date	Apr. 01, 2019
Facility Size	$ 225
Long-Term debt	$ 225	$ 225