Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 41	$ 37
Interest cost on projected benefit obligation	67	83
Expected return on plan assets	(143)	(143)
Amortization of actuarial loss	34	24
Amortization of prior service credit	(8)	(8)
Amortization of settlement charges	2
Net periodic pension costs	(7)	(7)
Duke Energy Carolinas
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	12
Interest cost on projected benefit obligation	16	20
Expected return on plan assets	(36)	(38)
Amortization of actuarial loss	7	6
Amortization of prior service credit	(2)	(2)
Amortization of settlement charges	1
Net periodic pension costs	(2)	(2)
Progress Energy
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	11
Interest cost on projected benefit obligation	21	26
Expected return on plan assets	(48)	(44)
Amortization of actuarial loss	11	9
Amortization of prior service credit	(1)	(1)
Amortization of settlement charges	1
Net periodic pension costs	(4)	1
Duke Energy Progress
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	6
Interest cost on projected benefit obligation	10	12
Expected return on plan assets	(22)	(23)
Amortization of actuarial loss	5	3
Net periodic pension costs	(1)	(2)
Duke Energy Florida
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	4
Interest cost on projected benefit obligation	12	14
Expected return on plan assets	(25)	(22)
Amortization of actuarial loss	6	6
Net periodic pension costs	(2)	2
Duke Energy Ohio
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	4	5
Expected return on plan assets	(7)	(8)
Amortization of actuarial loss	2	1
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	6	6
Expected return on plan assets	(11)	(11)
Amortization of actuarial loss	3	2
Net periodic pension costs		(1)
Piedmont Natural Gas
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	2	3
Expected return on plan assets	(5)	(5)
Amortization of actuarial loss	2	2
Amortization of prior service credit	(2)	(3)
Net periodic pension costs	$ (2)	$ (2)