Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 37	$ 45	$ 74	$ 90
Interest cost on projected benefit obligation	82	75	165	150
Expected return on plan assets	(143)	(140)	(286)	(280)
Amortization of actuarial loss (gain)	25	33	49	66
Amortization of prior service (credit) cost	(8)	(8)	(16)	(16)
Net periodic costs	(7)	5	(14)	10
Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	15	24	30
Interest cost on projected benefit obligation	21	18	41	36
Expected return on plan assets	(37)	(37)	(75)	(74)
Amortization of actuarial loss (gain)	5	7	11	14
Amortization of prior service (credit) cost	(2)	(2)	(4)	(4)
Net periodic costs	(1)	1	(3)	2
Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	10	13	21	26
Interest cost on projected benefit obligation	26	22	52	46
Expected return on plan assets	(45)	(43)	(89)	(88)
Amortization of actuarial loss (gain)	9	11	18	22
Amortization of prior service (credit) cost		(1)	(1)	(2)
Net periodic costs		2	1	4
Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	8	12	15
Interest cost on projected benefit obligation	12	10	24	21
Expected return on plan assets	(21)	(21)	(44)	(42)
Amortization of actuarial loss (gain)	3	5	6	10
Amortization of prior service (credit) cost	(1)	(1)	(1)	(1)
Net periodic costs	(1)	1	(3)	3
Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	6	10	11
Interest cost on projected benefit obligation	13	12	27	25
Expected return on plan assets	(22)	(23)	(44)	(46)
Amortization of actuarial loss (gain)	6	6	12	12
Amortization of prior service (credit) cost	(1)	(1)	(1)	(1)
Net periodic costs	2		4	1
Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1	2	2
Interest cost on projected benefit obligation	4	4	9	9
Expected return on plan assets	(6)	(7)	(14)	(14)
Amortization of actuarial loss (gain)		1	1	2
Net periodic costs	(1)	(1)	(2)	(1)
Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3	4	5
Interest cost on projected benefit obligation	7	6	13	12
Expected return on plan assets	(10)	(11)	(21)	(21)
Amortization of actuarial loss (gain)	1	2	3	4
Amortization of prior service (credit) cost	(1)		(1)
Net periodic costs	(1)		(2)
Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	3	4
Interest cost on projected benefit obligation	3	3	6	6
Expected return on plan assets	(6)	(6)	(11)	(12)
Amortization of actuarial loss (gain)	1	3	3	6
Amortization of prior service (credit) cost	(2)	(3)	(5)	(6)
Net periodic costs	$ (2)	$ (1)	$ (4)	$ (2)