Employee Benefit Plans (Projected Benefit Obligations Reconciliation of Funded Status to Net Amount Recognized) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	$ 77	$ 141	$ 19
Pension Plan | Duke Energy Carolinas
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	7	46	0
Pension Plan | Progress Energy
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	57	45	0
Pension Plan | Duke Energy Progress
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	4	25	0
Pension Plan | Duke Energy Florida
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	53	20	0
Pension Plan | Duke Energy Ohio
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	2	0	4
Pension Plan | Duke Energy Indiana
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	2	8	0
Pension Plan | Piedmont
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	1	0	11
Pension Plan | Qualified Plan
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	7,869	8,448
Service cost	150	174	159
Interest cost	317	299	328
Actuarial loss (gain)	716	(485)
Transfers	0	0
Benefits paid	(731)	(567)
Obligation at measurement date	8,321	7,869	8,448
Accumulated Benefit Obligation at measurement date	8,262	7,818
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	8,233	9,003
Employer contributions	77	141
Actual return on plan assets	1,331	(344)
Benefits paid	(731)	(567)
Transfers	0	0
Plan assets at measurement date	8,910	8,233	9,003
Funded status of plan	589	364
Pension Plan | Qualified Plan | Duke Energy Carolinas
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,954	2,029
Service cost	47	56	48
Interest cost	75	72	79
Actuarial loss (gain)	101	(44)
Transfers	11	0
Benefits paid	(265)	(159)
Obligation at measurement date	1,923	1,954	2,029
Accumulated Benefit Obligation at measurement date	1,923	1,954
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,168	2,372
Employer contributions	7	46
Actual return on plan assets	342	(91)
Benefits paid	(265)	(159)
Transfers	11	0
Plan assets at measurement date	2,263	2,168	2,372
Funded status of plan	340	214
Pension Plan | Qualified Plan | Progress Energy
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	2,433	2,637
Service cost	43	49	45
Interest cost	100	94	100
Actuarial loss (gain)	223	(204)
Transfers	0	0
Benefits paid	(191)	(143)
Obligation at measurement date	2,608	2,433	2,637
Accumulated Benefit Obligation at measurement date	2,578	2,404
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,606	2,814
Employer contributions	57	45
Actual return on plan assets	426	(110)
Benefits paid	(191)	(143)
Transfers	0	0
Plan assets at measurement date	2,898	2,606	2,814
Funded status of plan	290	173
Pension Plan | Qualified Plan | Duke Energy Progress
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,125	1,211
Service cost	25	28	26
Interest cost	45	43	47
Actuarial loss (gain)	87	(87)
Transfers	0	0
Benefits paid	(112)	(70)
Obligation at measurement date	1,170	1,125	1,211
Accumulated Benefit Obligation at measurement date	1,170	1,125
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,268	1,366
Employer contributions	4	25
Actual return on plan assets	204	(53)
Benefits paid	(112)	(70)
Transfers	0	0
Plan assets at measurement date	1,364	1,268	1,366
Funded status of plan	194	143
Pension Plan | Qualified Plan | Duke Energy Florida
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,295	1,410
Service cost	18	21	19
Interest cost	54	50	53
Actuarial loss (gain)	135	(114)
Transfers	0	0
Benefits paid	(78)	(72)
Obligation at measurement date	1,424	1,295	1,410
Accumulated Benefit Obligation at measurement date	1,392	1,265
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,322	1,429
Employer contributions	53	20
Actual return on plan assets	218	(55)
Benefits paid	(78)	(72)
Transfers	0	0
Plan assets at measurement date	1,515	1,322	1,429
Funded status of plan	91	27
Pension Plan | Qualified Plan | Duke Energy Ohio
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	435	479
Service cost	4	5	4
Interest cost	18	17	18
Actuarial loss (gain)	54	(29)
Transfers	0	0
Benefits paid	(30)	(37)
Obligation at measurement date	481	435	479
Accumulated Benefit Obligation at measurement date	471	425
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	405	458
Employer contributions	2	0
Actual return on plan assets	66	(16)
Benefits paid	(30)	(37)
Transfers	0	0
Plan assets at measurement date	443	405	458
Funded status of plan	(38)	(30)
Pension Plan | Qualified Plan | Duke Energy Indiana
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	618	669
Service cost	8	10	9
Interest cost	26	23	26
Actuarial loss (gain)	87	(29)
Transfers	0	0
Benefits paid	(46)	(55)
Obligation at measurement date	693	618	669
Accumulated Benefit Obligation at measurement date	686	614
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	611	684
Employer contributions	2	8
Actual return on plan assets	100	(26)
Benefits paid	(46)	(55)
Transfers	0	0
Plan assets at measurement date	667	611	684
Funded status of plan	(26)	(7)
Pension Plan | Qualified Plan | Piedmont
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	264	313
Service cost	5	7	10
Interest cost	10	11	14
Actuarial loss (gain)	33	(18)
Transfers	0	(16)
Benefits paid	(20)	(33)
Obligation at measurement date	292	264	313
Accumulated Benefit Obligation at measurement date	292	264
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	305	368
Employer contributions	1	0
Actual return on plan assets	49	(14)
Benefits paid	(20)	(33)
Transfers	0	(16)
Plan assets at measurement date	335	305	368
Funded status of plan	43	41
Other Post-Retirement Benefit Plans
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	728	813
Service cost	4	6	4
Interest cost	30	28	34
Plan participants' contributions	16	18
Actuarial loss (gain)	28	(51)
Transfers	0	0
Benefits paid	(83)	(86)
Obligation at measurement date	723	728	813
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	195	225
Employer contributions	60
Actual return on plan assets	32	(8)
Benefits paid	(83)	(86)
Employer contributions (reimbursements)		46
Plan participants' contributions	16	18
Plan assets at measurement date	220	195	225
Funded status of plan	(503)	(533)
Other Post-Retirement Benefit Plans | Duke Energy Carolinas
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	174	189
Service cost	1	1	1
Interest cost	7	7	8
Plan participants' contributions	3	3
Actuarial loss (gain)	9	(8)
Transfers	0	0
Benefits paid	(19)	(18)
Obligation at measurement date	175	174	189
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	115	133
Employer contributions	11
Actual return on plan assets	20	(5)
Benefits paid	(19)	(18)
Employer contributions (reimbursements)		2
Plan participants' contributions	3	3
Plan assets at measurement date	130	115	133
Funded status of plan	(45)	(59)
Other Post-Retirement Benefit Plans | Progress Energy
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	303	342
Service cost	1	1	0
Interest cost	12	12	13
Plan participants' contributions	6	6
Actuarial loss (gain)	13	(23)
Transfers	0	0
Benefits paid	(32)	(35)
Obligation at measurement date	303	303	342
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	0	0
Employer contributions	26
Actual return on plan assets	(1)	0
Benefits paid	(32)	(35)
Employer contributions (reimbursements)		29
Plan participants' contributions	6	6
Plan assets at measurement date	(1)	0	0
Funded status of plan	(304)	(303)
Other Post-Retirement Benefit Plans | Duke Energy Progress
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	166	184
Service cost	0	0	0
Interest cost	7	6	7
Plan participants' contributions	3	4
Actuarial loss (gain)	9	(9)
Transfers	0	0
Benefits paid	(17)	(19)
Obligation at measurement date	168	166	184
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	0	0
Employer contributions	13
Actual return on plan assets	0	0
Benefits paid	(17)	(19)
Employer contributions (reimbursements)		15
Plan participants' contributions	3	4
Plan assets at measurement date	(1)	0	0
Funded status of plan	(169)	(166)
Other Post-Retirement Benefit Plans | Duke Energy Florida
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	137	156
Service cost	1	1	0
Interest cost	5	6	6
Plan participants' contributions	2	3
Actuarial loss (gain)	5	(13)
Transfers	0	0
Benefits paid	(15)	(16)
Obligation at measurement date	135	137	156
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	0	0
Employer contributions	13
Actual return on plan assets	0	0
Benefits paid	(15)	(16)
Employer contributions (reimbursements)		13
Plan participants' contributions	2	3
Plan assets at measurement date	0	0	0
Funded status of plan	(135)	(137)
Other Post-Retirement Benefit Plans | Duke Energy Ohio
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	29	30
Service cost	0	1	0
Interest cost	1	1	1
Plan participants' contributions	1	1
Actuarial loss (gain)	1	(2)
Transfers	0	0
Benefits paid	(3)	(2)
Obligation at measurement date	29	29	30
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	8	7
Employer contributions	2
Actual return on plan assets	1	0
Benefits paid	(3)	(2)
Employer contributions (reimbursements)		2
Plan participants' contributions	1	1
Plan assets at measurement date	9	8	7
Funded status of plan	(20)	(21)
Other Post-Retirement Benefit Plans | Duke Energy Indiana
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	67	78
Service cost	1	1	0
Interest cost	3	3	3
Plan participants' contributions	2	2
Actuarial loss (gain)	2	(5)
Transfers	0	0
Benefits paid	(11)	(12)
Obligation at measurement date	64	67	78
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	5	11
Employer contributions	9
Actual return on plan assets	0	0
Benefits paid	(11)	(12)
Employer contributions (reimbursements)		4
Plan participants' contributions	2	2
Plan assets at measurement date	5	5	11
Funded status of plan	(59)	(62)
Other Post-Retirement Benefit Plans | Piedmont
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	30	32
Service cost	0	1	1
Interest cost	1	1	1
Plan participants' contributions	0	0
Actuarial loss (gain)	0	(1)
Transfers	0	(1)
Benefits paid	(1)	(2)
Obligation at measurement date	30	30	32
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	29	31
Employer contributions	0
Actual return on plan assets	6	(1)
Benefits paid	(1)	(2)
Employer contributions (reimbursements)		1
Plan participants' contributions	0	0
Plan assets at measurement date	34	29	$ 31
Funded status of plan	$ 4	$ (1)