Income Taxes (Other Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 126	$ 24	$ 25
Gross decreases – tax positions in prior periods	(2)	(3)	(2)
Gross increases – current period tax positions	4	105
Gross increases – tax positions in prior periods			7
Decreases due to settlements			(6)
Reduction due to lapse of statute of limitations	(3)
Total changes	(1)	102	(1)
Unrecognized tax benefits – December 31	125	126	24
Amount that if recognized, would affect the effective tax rate or regulatory liability	122
Duke Energy Carolinas
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	8	6	5
Gross decreases – tax positions in prior periods			(1)
Gross increases – current period tax positions	2	2
Gross increases – tax positions in prior periods			2
Total changes	2	2	1
Unrecognized tax benefits – December 31	10	8	6
Amount that if recognized, would affect the effective tax rate or regulatory liability	10
Progress Energy
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	9	9	5
Gross decreases – tax positions in prior periods		(1)
Gross increases – current period tax positions	1	1
Gross increases – tax positions in prior periods			4
Total changes	1	0	4
Unrecognized tax benefits – December 31	10	9	9
Amount that if recognized, would affect the effective tax rate or regulatory liability	10
Duke Energy Progress
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	6	6	5
Gross decreases – tax positions in prior periods		(1)
Gross increases – current period tax positions	0	1
Gross increases – tax positions in prior periods			1
Total changes		0	1
Unrecognized tax benefits – December 31	6	6	6
Amount that if recognized, would affect the effective tax rate or regulatory liability	6
Duke Energy Florida
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	3	3	5
Gross decreases – tax positions in prior periods			(4)
Gross increases – current period tax positions	0
Gross increases – tax positions in prior periods			2
Total changes		0	(2)
Unrecognized tax benefits – December 31	3	3	3
Amount that if recognized, would affect the effective tax rate or regulatory liability	3
Duke Energy Ohio
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	1	1	1
Gross increases – current period tax positions	0
Total changes			0
Unrecognized tax benefits – December 31	1	1	1
Amount that if recognized, would affect the effective tax rate or regulatory liability	1
Duke Energy Indiana
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	1	1	1
Total changes			0
Unrecognized tax benefits – December 31	1	1	1
Amount that if recognized, would affect the effective tax rate or regulatory liability	1
Piedmont
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	4	4	3
Gross increases – tax positions in prior periods			1
Reduction due to lapse of statute of limitations	(3)
Total changes	(3)		1
Unrecognized tax benefits – December 31	1	$ 4	$ 4
Amount that if recognized, would affect the effective tax rate or regulatory liability	$ 1