Variable Interest Entities (Sales and Cash Flows) (Details) - VIE not primary beneficiary - CRC - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Duke Energy Ohio
Variable Interest Entities [Line Items]
Receivables sold	$ 462	$ 479	$ 1,428	$ 1,483
Loss recognized on sale	2	4	8	11
Cash proceeds from receivables sold	449	471	1,439	1,516
Collection fees received	1		1	1
Return received on retained interests	1	1	3	5
Duke Energy Indiana
Variable Interest Entities [Line Items]
Receivables sold	717	762	1,947	2,172
Loss recognized on sale	3	4	9	13
Cash proceeds from receivables sold	689	762	1,941	2,200
Collection fees received			1	1
Return received on retained interests	$ 1	$ 2	$ 4	$ 7