Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 43	$ 41	$ 131	$ 124
Interest cost on projected benefit obligation	55	67	165	202
Expected return on plan assets	(139)	(143)	(418)	(429)
Amortization of actuarial loss	33	32	100	96
Amortization of prior service credit	(7)	(8)	(22)	(24)
Amortization of settlement charges	2	11	6	16
Net periodic pension costs	(13)		(38)	(15)
Duke Energy Carolinas
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	14	12	42	38
Interest cost on projected benefit obligation	13	16	38	47
Expected return on plan assets	(36)	(36)	(106)	(108)
Amortization of actuarial loss	7	7	22	21
Amortization of prior service credit	(2)	(2)	(6)	(6)
Amortization of settlement charges	1	6	4	8
Net periodic pension costs	(3)	3	(6)	0
Progress Energy
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12	38	36
Interest cost on projected benefit obligation	17	21	52	64
Expected return on plan assets	(47)	(48)	(141)	(143)
Amortization of actuarial loss	10	10	29	30
Amortization of prior service credit	(1)		(2)	(2)
Amortization of settlement charges	1	5	2	6
Net periodic pension costs	(7)		(22)	(9)
Duke Energy Progress
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	6	22	20
Interest cost on projected benefit obligation	8	10	23	29
Expected return on plan assets	(21)	(22)	(63)	(66)
Amortization of actuarial loss	5	4	14	13
Amortization of prior service credit			(1)	(1)
Amortization of settlement charges		5	1	6
Net periodic pension costs	(1)	3	(4)	1
Duke Energy Florida
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5	16	16
Interest cost on projected benefit obligation	10	12	29	35
Expected return on plan assets	(25)	(25)	(76)	(76)
Amortization of actuarial loss	5	6	15	17
Amortization of prior service credit	(1)		(1)	(1)
Amortization of settlement charges		1		1
Net periodic pension costs	(6)	(1)	(17)	(8)
Duke Energy Ohio
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	4	3
Interest cost on projected benefit obligation	2	4	9	12
Expected return on plan assets	(7)	(7)	(21)	(21)
Amortization of actuarial loss	2	2	5	5
Net periodic pension costs	(1)		(3)	(1)
Duke Energy Indiana
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	7	6
Interest cost on projected benefit obligation	5	6	14	17
Expected return on plan assets	(10)	(11)	(30)	(32)
Amortization of actuarial loss	3	3	10	9
Amortization of prior service credit			(1)	(1)
Amortization of settlement charges		1		1
Net periodic pension costs		1
Piedmont
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1	4	4
Interest cost on projected benefit obligation	2	2	6	7
Expected return on plan assets	(5)	(5)	(15)	(16)
Amortization of actuarial loss	2	2	7	7
Amortization of prior service credit	(1)	(2)	(6)	(7)
Amortization of settlement charges	$ 1	1	1	1
Net periodic pension costs		$ (1)	$ (3)	$ (4)