Employee Benefit Plans (Projected Benefit Obligations Reconciliation of Funded Status to Net Amount Recognized) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	$ 0	$ 77	$ 141
Pension Plan | Duke Energy Carolinas
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	7	46
Pension Plan | Progress Energy
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	57	45
Pension Plan | Duke Energy Progress
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	4	25
Pension Plan | Duke Energy Florida
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	53	20
Pension Plan | Duke Energy Ohio
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	2	0
Pension Plan | Duke Energy Indiana
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	2	8
Pension Plan | Piedmont
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	0	1	0
Pension Plan | Qualified Plan
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	8,321	7,869
Service cost	157	150	182
Interest cost	269	317	299
Actuarial loss	433	716
Transfers	0	0
Benefits paid	(541)	(731)
Benefits paid – settlements	(5)
Obligation at measurement date	8,634	8,321	7,869
Accumulated Benefit Obligation at measurement date	8,577	8,262
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	8,910	8,233
Employer contributions		77
Actual return on plan assets	973	1,331
Benefits paid	(541)	(731)
Benefits paid – settlements	(5)
Transfers	0	0
Plan assets at measurement date	9,337	8,910	8,233
Funded status of plan	703	589
Pension Plan | Qualified Plan | Duke Energy Carolinas
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,923	1,954
Service cost	49	47	58
Interest cost	62	75	72
Actuarial loss	83	101
Transfers	8	11
Benefits paid	(137)	(265)
Benefits paid – settlements	0
Obligation at measurement date	1,988	1,923	1,954
Accumulated Benefit Obligation at measurement date	1,989	1,923
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,263	2,168
Employer contributions		7
Actual return on plan assets	247	342
Benefits paid	(137)	(265)
Benefits paid – settlements	0
Transfers	8	11
Plan assets at measurement date	2,381	2,263	2,168
Funded status of plan	393	340
Pension Plan | Qualified Plan | Progress Energy
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	2,608	2,433
Service cost	46	43	51
Interest cost	85	100	94
Actuarial loss	144	223
Transfers	(8)	0
Benefits paid	(160)	(191)
Benefits paid – settlements	0
Obligation at measurement date	2,715	2,608	2,433
Accumulated Benefit Obligation at measurement date	2,684	2,578
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,898	2,606
Employer contributions		57
Actual return on plan assets	319	426
Benefits paid	(160)	(191)
Benefits paid – settlements	0
Transfers	(8)	0
Plan assets at measurement date	3,049	2,898	2,606
Funded status of plan	334	290
Pension Plan | Qualified Plan | Duke Energy Progress
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,170	1,125
Service cost	26	25	29
Interest cost	38	45	43
Actuarial loss	50	87
Transfers	(8)	0
Benefits paid	(83)	(112)
Benefits paid – settlements	0
Obligation at measurement date	1,193	1,170	1,125
Accumulated Benefit Obligation at measurement date	1,194	1,170
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,364	1,268
Employer contributions		4
Actual return on plan assets	149	204
Benefits paid	(83)	(112)
Benefits paid – settlements	0
Transfers	(8)	0
Plan assets at measurement date	1,422	1,364	1,268
Funded status of plan	229	194
Pension Plan | Qualified Plan | Duke Energy Florida
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,424	1,295
Service cost	20	18	22
Interest cost	46	54	50
Actuarial loss	93	135
Transfers	0	0
Benefits paid	(76)	(78)
Benefits paid – settlements	0
Obligation at measurement date	1,507	1,424	1,295
Accumulated Benefit Obligation at measurement date	1,476	1,392
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,515	1,322
Employer contributions		53
Actual return on plan assets	166	218
Benefits paid	(76)	(78)
Benefits paid – settlements	0
Transfers	0	0
Plan assets at measurement date	1,605	1,515	1,322
Funded status of plan	98	91
Pension Plan | Qualified Plan | Duke Energy Ohio
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	481	435
Service cost	4	4	5
Interest cost	15	18	17
Actuarial loss	21	54
Transfers	15	0
Benefits paid	(34)	(30)
Benefits paid – settlements	0
Obligation at measurement date	502	481	435
Accumulated Benefit Obligation at measurement date	493	471
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	443	405
Employer contributions		2
Actual return on plan assets	48	66
Benefits paid	(34)	(30)
Benefits paid – settlements	0
Transfers	15	0
Plan assets at measurement date	472	443	405
Funded status of plan	(30)	(38)
Pension Plan | Qualified Plan | Duke Energy Indiana
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	693	618
Service cost	8	8	11
Interest cost	22	26	23
Actuarial loss	46	87
Transfers	0	0
Benefits paid	(49)	(46)
Benefits paid – settlements	(5)
Obligation at measurement date	715	693	618
Accumulated Benefit Obligation at measurement date	709	686
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	667	611
Employer contributions		2
Actual return on plan assets	71	100
Benefits paid	(49)	(46)
Benefits paid – settlements	(5)
Transfers	0	0
Plan assets at measurement date	684	667	611
Funded status of plan	(31)	(26)
Pension Plan | Qualified Plan | Piedmont
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	292	264
Service cost	5	5	7
Interest cost	9	10	11
Actuarial loss	14	33
Transfers	0	0
Benefits paid	(27)	(20)
Benefits paid – settlements	0
Obligation at measurement date	293	292	264
Accumulated Benefit Obligation at measurement date	294	292
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	335	305
Employer contributions		1
Actual return on plan assets	35	49
Benefits paid	(27)	(20)
Benefits paid – settlements	0
Transfers	0	0
Plan assets at measurement date	343	335	305
Funded status of plan	50	43
Other Post-Retirement Benefit Plans
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	723	728
Service cost	4	4	6
Interest cost	23	30	28
Plan participants' contributions	15	16
Actuarial loss	19	28
Benefits paid	(75)	(83)
Obligation at measurement date	709	723	728
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	220	195
Employer contributions	53
Actual return on plan assets	24	32
Benefits paid	(75)	(83)
Plan participants' contributions	15	16
Employer contributions		60
Plan assets at measurement date	237	220	195
Funded status of plan	(472)	(503)
Other Post-Retirement Benefit Plans | Duke Energy Carolinas
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	175	174
Service cost	1	1	1
Interest cost	5	7	7
Plan participants' contributions	3	3
Actuarial loss	8	9
Benefits paid	(18)	(19)
Obligation at measurement date	174	175	174
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	130	115
Employer contributions	10
Actual return on plan assets	14	20
Benefits paid	(18)	(19)
Plan participants' contributions	3	3
Employer contributions		11
Plan assets at measurement date	139	130	115
Funded status of plan	(35)	(45)
Other Post-Retirement Benefit Plans | Progress Energy
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	303	303
Service cost	1	1	1
Interest cost	10	12	12
Plan participants' contributions	5	6
Actuarial loss	8	13
Benefits paid	(28)	(32)
Obligation at measurement date	299	303	303
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	(1)	0
Employer contributions	23
Actual return on plan assets	0	(1)
Benefits paid	(28)	(32)
Plan participants' contributions	5	6
Employer contributions		26
Plan assets at measurement date	(1)	(1)	0
Funded status of plan	(300)	(304)
Other Post-Retirement Benefit Plans | Duke Energy Progress
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	168	166
Service cost	0	0	0
Interest cost	5	7	6
Plan participants' contributions	3	3
Actuarial loss	5	9
Benefits paid	(15)	(17)
Obligation at measurement date	166	168	166
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	(1)	0
Employer contributions	11
Actual return on plan assets	0	0
Benefits paid	(15)	(17)
Plan participants' contributions	3	3
Employer contributions		13
Plan assets at measurement date	(2)	(1)	0
Funded status of plan	(168)	(169)
Other Post-Retirement Benefit Plans | Duke Energy Florida
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	135	137
Service cost	0	1	1
Interest cost	4	5	6
Plan participants' contributions	2	2
Actuarial loss	2	5
Benefits paid	(13)	(15)
Obligation at measurement date	130	135	137
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	0	0
Employer contributions	10
Actual return on plan assets	0	0
Benefits paid	(13)	(15)
Plan participants' contributions	2	2
Employer contributions		13
Plan assets at measurement date	(1)	0	0
Funded status of plan	(131)	(135)
Other Post-Retirement Benefit Plans | Duke Energy Ohio
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	29	29
Service cost	0	0	1
Interest cost	1	1	1
Plan participants' contributions	1	1
Actuarial loss	0	1
Benefits paid	(4)	(3)
Obligation at measurement date	27	29	29
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	9	8
Employer contributions	3
Actual return on plan assets	0	1
Benefits paid	(4)	(3)
Plan participants' contributions	1	1
Employer contributions		2
Plan assets at measurement date	9	9	8
Funded status of plan	(18)	(20)
Other Post-Retirement Benefit Plans | Duke Energy Indiana
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	64	67
Service cost	1	1	1
Interest cost	2	3	3
Plan participants' contributions	2	2
Actuarial loss	1	2
Benefits paid	(9)	(11)
Obligation at measurement date	61	64	67
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	5	5
Employer contributions	8
Actual return on plan assets	1	0
Benefits paid	(9)	(11)
Plan participants' contributions	2	2
Employer contributions		9
Plan assets at measurement date	7	5	5
Funded status of plan	(54)	(59)
Other Post-Retirement Benefit Plans | Piedmont
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	30	30
Service cost	0	0	1
Interest cost	1	1	1
Plan participants' contributions	0	0
Actuarial loss	1	0
Benefits paid	(2)	(1)
Obligation at measurement date	30	30	30
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	34	29
Employer contributions	1
Actual return on plan assets	4	6
Benefits paid	(2)	(1)
Plan participants' contributions	0	0
Employer contributions		0
Plan assets at measurement date	37	34	$ 29
Funded status of plan	$ 7	$ 4