Variable Interest Entities (Sales and Cash Flows)(Details) - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 481	$ 449	$ 1,442	$ 1,518
Loss recognized on sale	2	2	7	7
Cash proceeds from receivables sold	468	461	1,432	1,568
Collection fees received	1		1	1
Return received on retained interests	1		2	2
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	722	679	1,980	2,032
Loss recognized on sale	3	3	8	8
Cash proceeds from receivables sold	703	692	1,958	2,074
Collection fees received	0		1	1
Return received on retained interests	$ 2	$ 1	$ 4	$ 4