Variable Interest Entities (Sales and Cash Flows)(Details) (Variable Interest Entity, Not Primary Beneficiary [Member], Cinergy Receivables [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Duke Energy Ohio [Member]
Variable Interest Entity [Line Items]
Receivables sold	$ 2,246	$ 2,251	$ 2,154
Loss recognized on sale	11	12	13
Cash proceeds from receivables sold	2,261	2,220	2,172
Collection fees received	1	1	1
Return received on retained interests	4	5	5
Duke Energy Indiana [Member]
Variable Interest Entity [Line Items]
Receivables sold	2,913	2,985	2,773
Loss recognized on sale	11	11	12
Cash proceeds from receivables sold	2,932	2,944	2,784
Collection fees received	1	1	1
Return received on retained interests	$ 6	$ 6	$ 7