Variable Interest Entities (Sales and Cash Flows) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Cinergy Receivables [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables sold	$ 479	$ 450	$ 1,483	$ 1,478
Loss recognized on sale	4	4	11	10
Cash proceeds from receivables sold	471	449	1,516	1,499
Collection fees received			1	1
Return received on retained interests	1	2	5	5
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables sold	762	754	2,172	2,140
Loss recognized on sale	4	5	13	12
Cash proceeds from receivables sold	762	743	2,200	2,140
Collection fees received			1	1
Return received on retained interests	$ 2	$ 3	$ 7	$ 7