Variable Interest Entities (Sales and Cash Flows)(Details) - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 429	$ 425	$ 961	$ 1,069
Loss recognized on sale	2	2	5	5
Cash proceeds from receivables sold	427	467	964	1,107
Collection fees received	0	1	0	1
Return received on retained interests	0	1	1	2
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	623	637	1,258	1,353
Loss recognized on sale	2	2	5	5
Cash proceeds from receivables sold	612	660	1,255	1,382
Collection fees received	1	1	1	1
Return received on retained interests	$ 1	$ 1	$ 2	$ 3