Variable Interest Entities (Sales and Cash Flows)(Details) - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 425	$ 487	$ 1,069	$ 1,228
Loss recognized on sale	2	2	5	6
Cash proceeds from receivables sold	467	544	1,107	1,267
Collection fees received	1	1	1	1
Return received on retained interests	1	1	2	3
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	637	679	1,353	1,434
Loss recognized on sale	2	2	5	5
Cash proceeds from receivables sold	660	713	1,382	1,474
Collection fees received	1	1	1	1
Return received on retained interests	$ 1	$ 1	$ 3	$ 3