Employee Benefit Plans (Projected Benefit Obligations Reconciliation of Funded Status to Net Amount Recognized) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Pension Plan [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		$ 141	$ 19	$ 155
Pension Plan [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		8,448	8,131
Service cost		174	159	147
Interest cost		299	328	335
Actuarial loss (gain)		(485)	455
Plan amendments			(61)
Benefits paid		(567)	(537)
Impact of settlements			(27)
Obligation at measurement date	$ 8,131	7,869	8,448	8,131
Accumulated benefit obligation at measurement date		7,818	8,369
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		9,003	8,531
Actual return on plan assets		(344)	1,017
Benefits paid		(567)	(537)
Impact of Settlements			(27)
Employer contributions		141	19
Plan assets at measurement date	8,531	8,233	9,003	8,531
Funded status of plan		364	555
Pension Plan [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		331	332
Service cost		2	2	2
Interest cost		12	13	14
Actuarial loss (gain)		(17)	15
Benefits paid		(24)	(31)
Obligation at measurement date	332	304	331	332
Accumulated benefit obligation at measurement date		304	331
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(24)	(31)
Employer contributions		24	31
Pension Plan [Member] | Duke Energy Carolinas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		46		43
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		2,029	1,952
Service cost		56	48	48
Interest cost		72	79	86
Actuarial loss (gain)		(44)	68
Transfers			27
Benefits paid		(159)	(145)
Obligation at measurement date	1,952	1,954	2,029	1,952
Accumulated benefit obligation at measurement date		1,954	2,029
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,372	2,225
Actual return on plan assets		(91)	265
Benefits paid		(159)	(145)
Transfer of plan assets			27
Employer contributions		46
Plan assets at measurement date	2,225	2,168	2,372	2,225
Funded status of plan		214	343
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		14	14
Service cost		1	1
Interest cost			1	1
Benefits paid		(1)	(2)
Obligation at measurement date	14	14	14	14
Accumulated benefit obligation at measurement date		14	14
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(1)	(2)
Employer contributions		1	2
Pension Plan [Member] | Progress Energy [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		45		43
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		2,637	2,512
Service cost		49	45	42
Interest cost		94	100	106
Actuarial loss (gain)		(204)	158
Transfers			(32)
Benefits paid		(143)	(146)
Obligation at measurement date	2,512	2,433	2,637	2,512
Accumulated benefit obligation at measurement date		2,404	2,601
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,814	2,675
Actual return on plan assets		(110)	317
Benefits paid		(143)	(146)
Transfer of plan assets			(32)
Employer contributions		45
Plan assets at measurement date	2,675	2,606	2,814	2,675
Funded status of plan		173	177
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		116	114
Interest cost		4	5	5
Actuarial loss (gain)		(6)	5
Benefits paid		(8)	(8)
Obligation at measurement date	114	106	116	114
Accumulated benefit obligation at measurement date		106	116
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(8)	(8)
Employer contributions		8	8
Pension Plan [Member] | Duke Energy Progress [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		25		24
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,211	1,158
Service cost		28	26	24
Interest cost		43	47	49
Actuarial loss (gain)		(87)	57
Transfers			(2)
Benefits paid		(70)	(75)
Obligation at measurement date	1,158	1,125	1,211	1,158
Accumulated benefit obligation at measurement date		1,125	1,211
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,366	1,290
Actual return on plan assets		(53)	153
Benefits paid		(70)	(75)
Transfer of plan assets			(2)
Employer contributions		25
Plan assets at measurement date	1,290	1,268	1,366	1,290
Funded status of plan		143	155
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		35	33
Interest cost		1	1	1
Actuarial loss (gain)		(2)	4
Benefits paid		(3)	(3)
Obligation at measurement date	33	31	35	33
Accumulated benefit obligation at measurement date		31	35
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(3)	(3)
Employer contributions		3	3
Pension Plan [Member] | Duke Energy Florida [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		20		20
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,410	1,323
Service cost		21	19	19
Interest cost		50	53	55
Actuarial loss (gain)		(114)	99
Transfers			(15)
Benefits paid		(72)	(69)
Obligation at measurement date	1,323	1,295	1,410	1,323
Accumulated benefit obligation at measurement date		1,265	1,375
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,429	1,352
Actual return on plan assets		(55)	161
Benefits paid		(72)	(69)
Transfer of plan assets			(15)
Employer contributions		20
Plan assets at measurement date	1,352	1,322	1,429	1,352
Funded status of plan		27	19
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		47	46
Interest cost		2	2	2
Actuarial loss (gain)		(3)	2
Benefits paid		(3)	(3)
Obligation at measurement date	46	43	47	46
Accumulated benefit obligation at measurement date		43	47
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(3)	(3)
Employer contributions		3	3
Pension Plan [Member] | Duke Energy Ohio [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			4	5
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		479	447
Service cost		5	4	4
Interest cost		17	18	19
Actuarial loss (gain)		(29)	35
Transfers			12
Benefits paid		(37)	(37)
Obligation at measurement date	447	435	479	447
Accumulated benefit obligation at measurement date		425	468
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		458	428
Actual return on plan assets		(16)	51
Benefits paid		(37)	(37)
Transfer of plan assets			12
Employer contributions			4
Plan assets at measurement date	428	405	458	428
Funded status of plan		(30)	(21)
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		4	4
Actuarial loss (gain)		(1)
Obligation at measurement date	4	3	4	4
Accumulated benefit obligation at measurement date		3	4
Pension Plan [Member] | Duke Energy Indiana [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		8		9
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		669	658
Service cost		10	9	9
Interest cost		23	26	28
Actuarial loss (gain)		(29)	26
Benefits paid		(55)	(50)
Obligation at measurement date	658	618	669	658
Accumulated benefit obligation at measurement date		614	652
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		684	657
Actual return on plan assets		(26)	77
Benefits paid		(55)	(50)
Employer contributions		8
Plan assets at measurement date	657	611	684	657
Funded status of plan		(7)	15
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		3	3
Obligation at measurement date	3	3	3	3
Accumulated benefit obligation at measurement date		3	3
Pension Plan [Member] | Piedmont Natural Gas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	10		11		$ 10
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		313	344
Service cost	2	7	10		11
Interest cost	2	11	14		9
Actuarial loss (gain)		(18)	(38)
Transfers		(16)	0
Plan amendments			(61)
Benefits paid		(33)	(5)
Impact of settlements			(27)
Obligation at measurement date	344	264	313	344
Accumulated benefit obligation at measurement date		264	313
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		368	346
Actual return on plan assets		(14)	43
Benefits paid		(33)	(5)
Impact of Settlements			(27)
Transfer of plan assets		(16)	0
Employer contributions			11
Plan assets at measurement date	346	305	368	346
Funded status of plan		41	55
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		4	4
Service cost			0
Interest cost			0
Actuarial loss (gain)		(1)	0
Benefits paid			0
Obligation at measurement date	4	3	4	4
Accumulated benefit obligation at measurement date		3	4
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid			0
Employer contributions			0
Other Post-Retirement Benefit Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		813	868
Service cost		6	4	3
Interest cost		28	34	35
Plan participants' contributions		18	17
Actuarial loss (gain)		(51)	4
Plan amendments			(28)
Benefits paid		(86)	(86)
Obligation at measurement date	868	728	813	868
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		225	244
Actual return on plan assets		(8)	25
Benefits paid		(86)	(86)
Employer contributions (reimbursements)			25
Plan participants' contributions		18	17
Employer contributions		46
Plan assets at measurement date	244	195	225	244
Funded status of plan		(533)	(588)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		189	201
Service cost		1	1	1
Interest cost		7	8	8
Plan participants' contributions		3	3
Actuarial loss (gain)		(8)	(3)
Transfers			2
Plan amendments			(5)
Benefits paid		(18)	(18)
Obligation at measurement date	201	174	189	201
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		133	137
Actual return on plan assets		(5)	15
Benefits paid		(18)	(18)
Employer contributions (reimbursements)		2	(4)
Plan participants' contributions		3	3
Plan assets at measurement date	137	115	133	137
Funded status of plan		(59)	(56)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		342	357
Service cost		1		1
Interest cost		12	13	15
Plan participants' contributions		6	6
Actuarial loss (gain)		(23)	4
Transfers			(1)
Plan amendments			(3)
Benefits paid		(35)	(34)
Obligation at measurement date	357	303	342	357
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date			1
Actual return on plan assets			1
Benefits paid		(35)	(34)
Employer contributions (reimbursements)			26
Plan participants' contributions		6	6
Employer contributions		29
Plan assets at measurement date	1			1
Funded status of plan		(303)	(342)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		184	191
Interest cost		6	7	8
Plan participants' contributions		4	3
Actuarial loss (gain)		(9)	1
Plan amendments			(1)
Benefits paid		(19)	(17)
Obligation at measurement date	191	166	184	191
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(19)	(17)
Employer contributions (reimbursements)			14
Plan participants' contributions		4	3
Employer contributions		15
Funded status of plan		(166)	(184)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		156	164
Service cost		1		1
Interest cost		6	6	7
Plan participants' contributions		3	3
Actuarial loss (gain)		(13)	3
Transfers			(1)
Plan amendments			(2)
Benefits paid		(16)	(17)
Obligation at measurement date	164	137	156	164
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(16)	(17)
Employer contributions (reimbursements)			14
Plan participants' contributions		3	3
Employer contributions		13
Funded status of plan		(137)	(156)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		30	32
Service cost		1
Interest cost		1	1	1
Plan participants' contributions		1	1
Actuarial loss (gain)		(2)
Transfers			1
Plan amendments			(2)
Benefits paid		(2)	(3)
Obligation at measurement date	32	29	30	32
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		7	7
Actual return on plan assets			2
Benefits paid		(2)	(3)
Plan participants' contributions		1	1
Employer contributions		2
Plan assets at measurement date	7	8	7	7
Funded status of plan		(21)	(23)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		78	83
Service cost		1
Interest cost		3	3	4
Plan participants' contributions		2	2
Actuarial loss (gain)		(5)	3
Plan amendments			(2)
Benefits paid		(12)	(11)
Obligation at measurement date	83	67	78	83
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		11	22
Actual return on plan assets			1
Benefits paid		(12)	(11)
Employer contributions (reimbursements)		4	(3)
Plan participants' contributions		2	2
Plan assets at measurement date	22	5	11	22
Funded status of plan		(62)	(67)
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		32	39
Service cost		1	1		1
Interest cost		1	1		$ 1
Plan participants' contributions			0
Actuarial loss (gain)		(1)	1
Transfers		(1)	0
Plan amendments			(9)
Benefits paid		(2)	(1)
Obligation at measurement date	39	30	32	39
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		31	29
Actual return on plan assets		(1)	3
Benefits paid		(2)	(1)
Employer contributions (reimbursements)			0
Plan participants' contributions			0
Employer contributions		1
Plan assets at measurement date	$ 29	29	31	$ 29
Funded status of plan		$ (1)	$ (1)