Variable Interest Entities (Sales and Cash Flows)(Details) (Cinergy Receivables [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 512	$ 490	$ 1,150	$ 1,100
Gain (loss) recognized on sale	(3)	(3)	(6)	(7)
Cash proceeds from receivables sold	539	484	1,156	1,120
Return received on retained interests	2	1	3	3
Collection fees received	1	1	1	1
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	702	701	1,449	1,407
Gain (loss) recognized on sale	(3)	(3)	(6)	(6)
Cash proceeds from receivables sold	721	673	1,446	1,397
Return received on retained interests	1	1	3	3
Collection fees received	$ 1	$ 1	$ 1	$ 1