Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 37	$ 45
Interest cost on projected benefit obligation	83	75
Expected return on plan assets	(143)	(140)
Amortization of actuarial loss (gain)	24	33
Amortization of prior service (credit) cost	(8)	(8)
Net periodic costs	(7)	5
Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	15
Interest cost on projected benefit obligation	20	18
Expected return on plan assets	(38)	(37)
Amortization of actuarial loss (gain)	6	7
Amortization of prior service (credit) cost	(2)	(2)
Net periodic costs	(2)	1
Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	11	13
Interest cost on projected benefit obligation	26	24
Expected return on plan assets	(44)	(45)
Amortization of actuarial loss (gain)	9	11
Amortization of prior service (credit) cost	(1)	(1)
Net periodic costs	1	2
Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	7
Interest cost on projected benefit obligation	12	11
Expected return on plan assets	(23)	(21)
Amortization of actuarial loss (gain)	3	5
Net periodic costs	(2)	2
Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	4	5
Interest cost on projected benefit obligation	14	13
Expected return on plan assets	(22)	(23)
Amortization of actuarial loss (gain)	6	6
Net periodic costs	2	1
Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	5	5
Expected return on plan assets	(8)	(7)
Amortization of actuarial loss (gain)	1	1
Net periodic costs	(1)
Duke Energy Indiana [Member]
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)	(10)
Amortization of actuarial loss (gain)	2	2
Net periodic costs	(1)	0
Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	2
Interest cost on projected benefit obligation	3	3
Expected return on plan assets	(5)	(6)
Amortization of actuarial loss (gain)	2	3
Amortization of prior service (credit) cost	(3)	(3)
Net periodic costs	$ (2)	$ (1)