Variable Interest Entities (Sales and Cash Flows)(Details) (Cinergy Receivables [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 477	$ 514	$ 1,705	$ 1,664
Loss recognized on sale	3	3	9	9
Cash proceeds from receivables sold	494	518	1,761	1,674
Collection fees received			1	1
Return received on retained interests		1	3	4
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	739	765	2,173	2,214
Loss recognized on sale	3	2	8	8
Cash proceeds from receivables sold	759	758	2,233	2,204
Collection fees received			1	1
Return received on retained interests	$ 2	$ 2	$ 5	$ 5