Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 42	$ 47	$ 116	$ 137
Interest cost on projected benefit obligation	77	74	242	224
Expected return on plan assets	(140)	(140)	(426)	(420)
Amortization of actuarial loss (gain)	28	33	77	99
Amortization of prior service (credit) cost	(8)	(8)	(24)	(24)
Net periodic costs	(1)	6	(15)	16
Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	15	37	45
Interest cost on projected benefit obligation	17	18	58	54
Expected return on plan assets	(36)	(37)	(111)	(111)
Amortization of actuarial loss (gain)	6	7	17	21
Amortization of prior service (credit) cost	(2)	(2)	(6)	(6)
Net periodic costs	(2)	1	(5)	3
Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	13	34	39
Interest cost on projected benefit obligation	24	24	76	70
Expected return on plan assets	(45)	(45)	(134)	(133)
Amortization of actuarial loss (gain)	10	11	28	33
Amortization of prior service (credit) cost	(1)	(1)	(2)	(3)
Net periodic costs	1	2	2	6
Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	7	19	22
Interest cost on projected benefit obligation	10	10	34	31
Expected return on plan assets	(22)	(21)	(66)	(63)
Amortization of actuarial loss (gain)	4	6	10	16
Amortization of prior service (credit) cost			(1)	(1)
Net periodic costs	(1)	2	(4)	5
Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5	15	16
Interest cost on projected benefit obligation	14	13	41	38
Expected return on plan assets	(22)	(23)	(66)	(69)
Amortization of actuarial loss (gain)	6	6	18	18
Amortization of prior service (credit) cost			(1)	(1)
Net periodic costs	3	1	7	2
Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	2	3	4
Interest cost on projected benefit obligation	5	4	14	13
Expected return on plan assets	(7)	(7)	(21)	(21)
Amortization of actuarial loss (gain)	2	1	3	3
Net periodic costs	1		(1)	(1)
Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	6	7
Interest cost on projected benefit obligation	6	6	19	18
Expected return on plan assets	(11)	(10)	(32)	(31)
Amortization of actuarial loss (gain)	3	2	6	6
Amortization of prior service (credit) cost			(1)
Net periodic costs			(2)
Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	2	4	6
Interest cost on projected benefit obligation	2	3	8	9
Expected return on plan assets	(5)	(6)	(16)	(18)
Amortization of actuarial loss (gain)	2	3	5	9
Amortization of prior service (credit) cost	(2)	(3)	(7)	(9)
Net periodic costs	$ (2)	$ (1)	$ (6)	$ (3)