Variable Interest Entities (Sales and Cash Flows) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 429	$ 461	$ 1,004	$ 1,028
Loss recognized on sale	3	3	7	6
Cash proceeds from receivables sold	448	465	1,045	1,050
Collection fees received	1	1	1	1
Return received on retained interests	2	1	4	3
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	676	692	1,410	1,386
Loss recognized on sale	4	4	9	7
Cash proceeds from receivables sold	680	686	1,438	1,397
Collection fees received	1	1	1	1
Return received on retained interests	$ 2	$ 2	$ 5	$ 4