Income Taxes (Other Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 24	$ 25	$ 17
Gross increases – tax positions in prior periods	105	7	12
Gross decreases – tax positions in prior periods	(3)	(2)	(4)
Decreases due to settlements		(6)
Total changes	102	(1)	8
Unrecognized tax benefits – December 31	126	24	25
Amount that if recognized, would affect the effective tax rate or regulatory liability	122
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	16	2
Interest receivable related to income taxes	1
Interest payable related to income taxes	1	3	5
Duke Energy Carolinas
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	6	5	1
Gross increases – tax positions in prior periods	2	2	4
Gross decreases – tax positions in prior periods		(1)
Total changes	2	1	4
Unrecognized tax benefits – December 31	8	6	5
Amount that if recognized, would affect the effective tax rate or regulatory liability	8
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest expense recognized related to income taxes			2
Interest payable related to income taxes			25
Progress Energy
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	9	5	2
Gross increases – tax positions in prior periods	1	4	3
Gross decreases – tax positions in prior periods	(1)
Total changes		4	3
Unrecognized tax benefits – December 31	9	9	5
Amount that if recognized, would affect the effective tax rate or regulatory liability	9
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	1		1
Interest payable related to income taxes		1	1
Duke Energy Progress
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	6	5	2
Gross increases – tax positions in prior periods	1	1	3
Gross decreases – tax positions in prior periods	(1)
Total changes		1	3
Unrecognized tax benefits – December 31	6	6	5
Amount that if recognized, would affect the effective tax rate or regulatory liability	6
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	1
Interest payable related to income taxes		1	1
Duke Energy Florida
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	3	5	4
Gross increases – tax positions in prior periods		2	1
Gross decreases – tax positions in prior periods		(4)
Total changes		(2)	1
Unrecognized tax benefits – December 31	3	3	5
Amount that if recognized, would affect the effective tax rate or regulatory liability	3
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes			1
Duke Energy Ohio
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	1	1	4
Gross increases – tax positions in prior periods			1
Gross decreases – tax positions in prior periods			(4)
Total changes			(3)
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
Gross increases – tax positions in prior periods			1
Total changes			1
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	3
Gross increases – tax positions in prior periods		1	3
Total changes		1	3
Unrecognized tax benefits – December 31	4	$ 4	$ 3
Amount that if recognized, would affect the effective tax rate or regulatory liability	4
Income Tax Examination, Penalties and Interest Expense [Abstract]
Interest payable related to income taxes	$ 1