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, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Pension Plan [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		$ 19	$ 155		$ 302
Pension Plan [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		8,131	7,727
Obligation assumed from acquisition			352
Service cost		159	147		159
Interest cost		328	335		324
Actuarial loss (gain)		455	307
Plan amendments		(61)	(52)
Benefits paid		(537)	(679)
Impact of settlements		(27)	(6)
Obligation at measurement date	$ 8,131	8,448	8,131		7,727
Accumulated benefit obligation at measurement date	8,006	8,369	8,006
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		8,531	8,136
Assets received from acquisition			343
Employer contributions		19	155
Actual return on plan assets		1,017	582
Benefits paid		(537)	(679)
Impact of Settlements		(27)	(6)
Plan assets at measurement date	8,531	9,003	8,531		8,136
Funded status of plan	400	555	400
Pension Plan [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		332	341
Obligation assumed from acquisition			5
Service cost		2	2		3
Interest cost		13	14		13
Actuarial loss (gain)		15	4
Plan amendments			(2)
Benefits paid		(31)	(32)
Obligation at measurement date	332	331	332		341
Accumulated benefit obligation at measurement date	332	331	332
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		31	32
Benefits paid		(31)	(32)
Pension Plan [Member] | Duke Energy Carolinas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			43		91
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,952	1,995
Service cost		48	48		50
Interest cost		79	86		83
Actuarial loss (gain)		68	46
Transfers		27	14
Plan amendments			(3)
Benefits paid		(145)	(234)
Obligation at measurement date	1,952	2,029	1,952		1,995
Accumulated benefit obligation at measurement date	1,952	2,029	1,952
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,225	2,243
Employer contributions			43
Actual return on plan assets		265	159
Benefits paid		(145)	(234)
Transfer of plan assets		27	14
Plan assets at measurement date	2,225	2,372	2,225		2,243
Funded status of plan	273	343	273
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		14	16
Service cost		1
Interest cost		1	1		1
Actuarial loss (gain)			(1)
Benefits paid		(2)	(2)
Obligation at measurement date	14	14	14		16
Accumulated benefit obligation at measurement date	14	14	14
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		2	2
Benefits paid		(2)	(2)
Pension Plan [Member] | Progress Energy [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			43		83
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		2,512	2,451
Service cost		45	42		44
Interest cost		100	106		104
Actuarial loss (gain)		158	111
Transfers		(32)	(3)
Benefits paid		(146)	(195)
Obligation at measurement date	2,512	2,637	2,512		2,451
Accumulated benefit obligation at measurement date	2,479	2,601	2,479
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		2,675	2,640
Employer contributions			43
Actual return on plan assets		317	190
Benefits paid		(146)	(195)
Transfer of plan assets		(32)	(3)
Plan assets at measurement date	2,675	2,814	2,675		2,640
Funded status of plan	163	177	163
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		114	112
Service cost					1
Interest cost		5	5		4
Actuarial loss (gain)		5	5
Benefits paid		(8)	(8)
Obligation at measurement date	114	116	114		112
Accumulated benefit obligation at measurement date	114	116	114
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		8	8
Benefits paid		(8)	(8)
Pension Plan [Member] | Duke Energy Progress [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			24		42
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,158	1,143
Service cost		26	24		23
Interest cost		47	49		48
Actuarial loss (gain)		57	52
Transfers		(2)	(3)
Benefits paid		(75)	(107)
Obligation at measurement date	1,158	1,211	1,158		1,143
Accumulated benefit obligation at measurement date	1,158	1,211	1,158
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,290	1,284
Employer contributions			24
Actual return on plan assets		153	92
Benefits paid		(75)	(107)
Transfer of plan assets		(2)	(3)
Plan assets at measurement date	1,290	1,366	1,290		1,284
Funded status of plan	132	155	132
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		33	33
Interest cost		1	1		1
Actuarial loss (gain)		4	2
Benefits paid		(3)	(3)
Obligation at measurement date	33	35	33		33
Accumulated benefit obligation at measurement date	33	35	33
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		3	3
Benefits paid		(3)	(3)
Pension Plan [Member] | Duke Energy Florida [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			20		40
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		1,323	1,276
Service cost		19	19		20
Interest cost		53	55		54
Actuarial loss (gain)		99	57
Transfers		(15)
Benefits paid		(69)	(84)
Obligation at measurement date	1,323	1,410	1,323		1,276
Accumulated benefit obligation at measurement date	1,290	1,375	1,290
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1,352	1,321
Employer contributions			20
Actual return on plan assets		161	95
Benefits paid		(69)	(84)
Transfer of plan assets		(15)
Plan assets at measurement date	1,352	1,429	1,352		1,321
Funded status of plan	29	19	29
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		46	46
Interest cost		2	2		2
Actuarial loss (gain)		2	1
Benefits paid		(3)	(3)
Obligation at measurement date	46	47	46		46
Accumulated benefit obligation at measurement date	46	47	46
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		3	3
Benefits paid		(3)	(3)
Pension Plan [Member] | Duke Energy Ohio [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		4	5		8
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		447	453
Service cost		4	4		4
Interest cost		18	19		18
Actuarial loss (gain)		35	13
Transfers		12	(3)
Plan amendments			(3)
Benefits paid		(37)	(36)
Obligation at measurement date	447	479	447		453
Accumulated benefit obligation at measurement date	436	468	436
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		428	433
Employer contributions		4	5
Actual return on plan assets		51	29
Benefits paid		(37)	(36)
Transfer of plan assets		12	(3)
Plan assets at measurement date	428	458	428		433
Funded status of plan	(19)	(21)	(19)
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		4	4
Obligation at measurement date	4	4	4		4
Accumulated benefit obligation at measurement date	4	4	4
Pension Plan [Member] | Duke Energy Indiana [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions			9		19
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		658	649
Service cost		9	9		10
Interest cost		26	28		27
Actuarial loss (gain)		26	41
Plan amendments			(15)
Benefits paid		(50)	(54)
Obligation at measurement date	658	669	658		649
Accumulated benefit obligation at measurement date	649	652	649
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		657	655
Employer contributions			9
Actual return on plan assets		77	47
Benefits paid		(50)	(54)
Plan assets at measurement date	657	684	657		655
Funded status of plan	(1)	15	(1)
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		3	5
Actuarial loss (gain)			(2)
Obligation at measurement date	3	3	3		5
Accumulated benefit obligation at measurement date	3	3	3
Pension Plan [Member] | Piedmont Natural Gas [Member]
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions	10	11		$ 10		$ 10
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	352	344		312
Service cost	2	10		11		11
Interest cost	2	14		9		12
Actuarial loss (gain)	(5)	38		34
Plan amendments		(61)
Benefits paid	(1)	(5)		(14)
Impact of settlements	(6)	(27)
Obligation at measurement date	344	313	344	352		312
Accumulated benefit obligation at measurement date	289	313	289	296
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	343	346		329
Employer contributions	10	11		10
Actual return on plan assets		43		18
Benefits paid	(1)	(5)		(14)
Impact of Settlements	(6)	(27)
Plan assets at measurement date	346	368	346	343		329
Funded status of plan	2	55	2	(9)
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	5	4		6
Actuarial loss (gain)	(1)
Impact of settlements				(1)
Obligation at measurement date	4	4	4	5		6
Accumulated benefit obligation at measurement date		4		5
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date				1
Impact of Settlements				(1)
Plan assets at measurement date						1
Other Post-Retirement Benefit Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		868	828
Obligation assumed from acquisition			39
Service cost		4	3		6
Interest cost		34	35		36
Plan participants' contributions		17	19
Actuarial loss (gain)		4	33
Plan amendments		(28)	(1)
Benefits paid		(86)	(88)
Obligation at measurement date	868	813	868		828
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		244	208
Assets received from acquisition			29
Employer contributions		25	62
Actual return on plan assets		25	14
Benefits paid		(86)	(88)
Plan participants' contributions		17	19
Plan assets at measurement date	244	225	244		208
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		201	200
Service cost		1	1		1
Interest cost		8	8		9
Plan participants' contributions		3	3
Actuarial loss (gain)		(3)	5
Transfers		2	1
Plan amendments		(5)
Benefits paid		(18)	(17)
Obligation at measurement date	201	189	201		200
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		137	134
Employer contributions			9
Actual return on plan assets		15	8
Benefits paid		(18)	(17)
Employer contributions (reimbursements)		(4)
Plan participants' contributions		3	3
Plan assets at measurement date	137	133	137		134
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		357	354
Service cost			1		1
Interest cost		13	15		15
Plan participants' contributions		6	7
Actuarial loss (gain)		4	16
Transfers		(1)
Plan amendments		(3)
Benefits paid		(34)	(36)
Obligation at measurement date	357	342	357		354
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		1
Employer contributions		26	29
Actual return on plan assets		1	1
Benefits paid		(34)	(36)
Plan participants' contributions		6	7
Plan assets at measurement date	1		1
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		191	188
Service cost					1
Interest cost		7	8		8
Plan participants' contributions		3	4
Actuarial loss (gain)		1	8
Plan amendments		(1)
Benefits paid		(17)	(17)
Obligation at measurement date	191	184	191		188
Change in Fair Value of Plan Assets [Rollforward]
Employer contributions		14	13
Benefits paid		(17)	(17)
Plan participants' contributions		3	4
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		164	164
Service cost			1		1
Interest cost		6	7		7
Plan participants' contributions		3	3
Actuarial loss (gain)		3	8
Transfers		(1)
Plan amendments		(2)
Benefits paid		(17)	(19)
Obligation at measurement date	164	156	164		164
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date			1
Employer contributions		14	15
Benefits paid		(17)	(19)
Plan participants' contributions		3	3
Plan assets at measurement date					1
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		32	35
Interest cost		1	1		2
Plan participants' contributions		1	1
Transfers		1
Plan amendments		(2)	(1)
Benefits paid		(3)	(4)
Obligation at measurement date	32	30	32		35
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		7	8
Employer contributions			1
Actual return on plan assets		2	1
Benefits paid		(3)	(4)
Plan participants' contributions		1	1
Plan assets at measurement date	7	7	7		8
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date		83	87
Service cost					1
Interest cost		3	4		4
Plan participants' contributions		2	2
Actuarial loss (gain)		3	3
Plan amendments		(2)
Benefits paid		(11)	(13)
Obligation at measurement date	83	78	83		87
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date		22	19
Employer contributions			12
Actual return on plan assets		1	2
Benefits paid		(11)	(13)
Employer contributions (reimbursements)		(3)
Plan participants' contributions		2	2
Plan assets at measurement date	22	11	22		$ 19
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	39	39		38
Service cost		1		1		1
Interest cost		1		1		2
Actuarial loss (gain)		1		2
Plan amendments		(9)
Benefits paid		(1)		(3)
Obligation at measurement date	39	32	39	39		38
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	29	29		28
Employer contributions				3
Actual return on plan assets		3		1
Benefits paid		(1)		(3)
Plan assets at measurement date	$ 29	$ 31	$ 29	$ 29		$ 28