Variable Interest Entities (Sales and Cash Flows)(Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 438	$ 481	$ 1,392	$ 1,442
Loss recognized on sale	2	2	7	7
Cash proceeds from receivables sold	434	468	1,421	1,432
Collection fees received	1	1	1	1
Return received on retained interests	0	1	2	2
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	720	722	2,047	1,980
Loss recognized on sale	3	3	9	8
Cash proceeds from receivables sold	713	703	2,064	1,958
Collection fees received	0		1	1
Return received on retained interests	$ 2	$ 2	$ 5	$ 4