Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 44	$ 41
Interest cost on projected benefit obligation	55	67
Expected return on plan assets	(139)	(143)
Amortization of actuarial loss	33	34
Amortization of prior service credit	(7)	(8)
Amortization of settlement charges	2	2
Net periodic pension costs	(12)	(7)
Duke Energy Carolinas
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	14	12
Interest cost on projected benefit obligation	13	16
Expected return on plan assets	(35)	(36)
Amortization of actuarial loss	7	7
Amortization of prior service credit	(2)	(2)
Amortization of settlement charges	1	1
Net periodic pension costs	(2)	(2)
Progress Energy
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12
Interest cost on projected benefit obligation	17	21
Expected return on plan assets	(47)	(48)
Amortization of actuarial loss	10	11
Amortization of prior service credit	(1)	(1)
Amortization of settlement charges	1	1
Net periodic pension costs	(7)	(4)
Duke Energy Progress
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	6
Interest cost on projected benefit obligation	7	10
Expected return on plan assets	(21)	(22)
Amortization of actuarial loss	5	5
Net periodic pension costs	(2)	(1)
Duke Energy Florida
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5
Interest cost on projected benefit obligation	10	12
Expected return on plan assets	(26)	(25)
Amortization of actuarial loss	5	6
Net periodic pension costs	(6)	(2)
Duke Energy Ohio
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	3	4
Expected return on plan assets	(7)	(7)
Amortization of actuarial loss	2	2
Net periodic pension costs	(1)
Duke Energy Indiana
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2
Interest cost on projected benefit obligation	5	6
Expected return on plan assets	(10)	(11)
Amortization of actuarial loss	3	3
Piedmont
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	2	2
Expected return on plan assets	(5)	(5)
Amortization of actuarial loss	2	2
Amortization of prior service credit	(1)	(2)
Net periodic pension costs	$ (1)	$ (2)