Employee Benefit Plans (Projected Benefit Obligations Reconciliation of Funded Status to Net Amount Recognized) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	$ 8,107	$ 7,510
Defined Benefit Plan, Other Changes	(83)
Service cost	159	135	$ 167
Interest cost on projected benefit obligation	324	344	320
Actuarial (gains) losses	(241)	618
Plan amendments	(6)	(4)
Benefits paid	(533)	(496)
Obligation at measurement date	7,727	8,107	7,510
Accumulated benefit obligation at measurement date	7,606	7,966
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	8,498	8,142
Defined Benefit Plan, Divestitures, Plan Assets	(81)
Actual return on plan assets	(50)	852
Benefits paid	(533)	(496)
Employer contributions	302		250
Plan assets at measurement date	8,136	8,498	8,142
Funded status of plan	409	391
Pension Plan [Member] | Change in Assumptions for Pension Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Actuarial (gains) losses		180
Pension Plan [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	2,053	1,875
Service cost	50	41	49
Interest cost on projected benefit obligation	83	85	80
Actuarial (gains) losses	(53)	132
Transfers of benefit obligation	8	37
Plan amendments		(1)
Benefits paid	(146)	(116)
Obligation at measurement date	1,995	2,053	1,875
Accumulated benefit obligation at measurement date	1,993	2,052
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,300	2,162
Actual return on plan assets	(10)	217
Benefits paid	(146)	(116)
Transfer of plan assets	8	37
Employer contributions	91
Plan assets at measurement date	2,243	2,300	2,162
Funded status of plan	248	247
Pension Plan [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	2,557	2,739
Service cost	44	40	60
Interest cost on projected benefit obligation	104	112	116
Actuarial (gains) losses	(111)	211
Transfers of benefit obligation	4	(375)
Benefits paid	(147)	(170)
Obligation at measurement date	2,451	2,557	2,739
Accumulated benefit obligation at measurement date	2,414	2,519
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	2,722	2,944
Actual return on plan assets	(22)	300
Benefits paid	(147)	(170)
Transfer of plan assets	4	(352)
Employer contributions	83		250
Plan assets at measurement date	2,640	2,722	2,944
Funded status of plan	189	165
Pension Plan [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,187	1,172
Service cost	23	21	22
Interest cost on projected benefit obligation	48	54	50
Actuarial (gains) losses	(46)	98
Transfers of benefit obligation	7	(61)
Benefits paid	(76)	(97)
Obligation at measurement date	1,143	1,187	1,172
Accumulated benefit obligation at measurement date	1,143	1,187
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,321	1,330
Actual return on plan assets	(10)	149
Benefits paid	(76)	(97)
Transfer of plan assets	7	(61)
Employer contributions	42		63
Plan assets at measurement date	1,284	1,321	1,330
Funded status of plan	141	134
Pension Plan [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	1,335	1,233
Service cost	20	20	30
Interest cost on projected benefit obligation	54	57	53
Actuarial (gains) losses	(62)	105
Transfers of benefit obligation	(3)	(9)
Benefits paid	(68)	(71)
Obligation at measurement date	1,276	1,335	1,233
Accumulated benefit obligation at measurement date	1,240	1,297
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	1,363	1,299
Actual return on plan assets	(11)	144
Benefits paid	(68)	(71)
Transfer of plan assets	(3)	(9)
Employer contributions	40		133
Plan assets at measurement date	1,321	1,363	1,299
Funded status of plan	45	28
Pension Plan [Member] | Duke Energy Ohio [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	469	442
Service cost	4	4	6
Interest cost on projected benefit obligation	18	20	21
Actuarial (gains) losses	(9)	41
Transfers of benefit obligation	8	(6)
Plan amendments		(1)
Benefits paid	(37)	(31)
Obligation at measurement date	453	469	442
Accumulated benefit obligation at measurement date	442	459
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	456	448
Actual return on plan assets	(2)	45
Benefits paid	(37)	(31)
Transfer of plan assets	8	(6)
Employer contributions	8
Plan assets at measurement date	433	456	448
Funded status of plan	(20)	(13)
Pension Plan [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	673	632
Service cost	10	9	11
Interest cost on projected benefit obligation	27	29	28
Actuarial (gains) losses	(15)	41
Plan amendments	(4)
Benefits paid	(42)	(38)
Obligation at measurement date	649	673	632
Accumulated benefit obligation at measurement date	628	645
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	681	654
Actual return on plan assets	(3)	65
Benefits paid	(42)	(38)
Employer contributions	19
Plan assets at measurement date	655	681	654
Funded status of plan	6	8
Non Qualified Pension Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	337	304
Service cost	3	3	3
Interest cost on projected benefit obligation	13	14	13
Actuarial (gains) losses	10	43
Transfers of benefit obligation	4
Benefits paid	(26)	(27)
Obligation at measurement date	341	337	304
Accumulated benefit obligation at measurement date	336	333
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid	(26)	(27)
Employer contributions	26	27
Non Qualified Pension Plans [Member] | Change in Assumptions for Pension Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Actuarial (gains) losses		21
Non Qualified Pension Plans [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	16	15
Interest cost on projected benefit obligation	1	1	1
Actuarial (gains) losses	1	2
Benefits paid	(2)	(2)
Obligation at measurement date	16	16	15
Accumulated benefit obligation at measurement date	16	15
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid	(2)	(2)
Employer contributions	2	2
Non Qualified Pension Plans [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	116	140
Service cost	1	1	1
Interest cost on projected benefit obligation	4	5	7
Actuarial (gains) losses	(1)	11
Transfers of benefit obligation		(32)
Benefits paid	(8)	(9)
Obligation at measurement date	112	116	140
Accumulated benefit obligation at measurement date	112	116
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid	(8)	(9)
Employer contributions	8	9
Non Qualified Pension Plans [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	35	34
Service cost		1	1
Interest cost on projected benefit obligation	1	1	1
Actuarial (gains) losses		2
Benefits paid	(3)	(3)
Obligation at measurement date	33	35	34
Accumulated benefit obligation at measurement date	33	35
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid	(3)	(3)
Employer contributions	3	3
Non Qualified Pension Plans [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	61	39
Interest cost on projected benefit obligation	2	2	1
Actuarial (gains) losses	(14)	20
Transfers of benefit obligation		4
Benefits paid	(3)	(4)
Obligation at measurement date	46	61	39
Accumulated benefit obligation at measurement date	46	61
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid	(3)	(4)
Employer contributions	3	4
Non Qualified Pension Plans [Member] | Duke Energy Ohio [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	4	3
Actuarial (gains) losses		1
Obligation at measurement date	4	4	3
Accumulated benefit obligation at measurement date	4	4
Non Qualified Pension Plans [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	5	5
Actuarial (gains) losses		1
Settlements		0
Benefits paid		(1)
Obligation at measurement date	5	5	5
Accumulated benefit obligation at measurement date	5	5
Change in Fair Value of Plan Assets [Rollforward]
Benefits paid		(1)
Employer contributions		1
Other Post-Retirement Benefit Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	916	1,106
Defined Benefit Plan, Other Changes	(3)
Service cost	6	10	24
Interest cost on projected benefit obligation	36	49	68
Plan participants' contributions	20	25
Actuarial (gains) losses	(39)	(87)
Plan amendments	(9)	(85)
Benefits paid	(100)	(103)
Accrued retiree drug subsidy	1	1
Obligation at measurement date	828	916	1,106
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	227	214
Actual return on plan assets	(1)	18
Benefits paid	(100)	(103)
Employer contributions	62	73
Plan participants' contributions	20	25
Plan assets at measurement date	208	227	214
Other Post-Retirement Benefit Plans [Member] | Change in Assumptions for Pension Plans [Member]
Change in Projected Benefit Obligation [Rollforward]
Actuarial (gains) losses		7
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	220	265
Service cost	1	2	2
Interest cost on projected benefit obligation	9	12	13
Plan participants' contributions	4	10
Actuarial (gains) losses	(18)	(35)
Transfers of benefit obligation	2	1
Plan amendments		(4)
Benefits paid	(18)	(31)
Obligation at measurement date	200	220	265
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	145	143
Actual return on plan assets	(1)	12
Benefits paid	(18)	(31)
Transfer of plan assets		(1)
Employer contributions	4	12
Plan participants' contributions	4	10
Plan assets at measurement date	134	145	143
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	379	533
Service cost	1	4	18
Interest cost on projected benefit obligation	15	22	41
Plan participants' contributions	7	8
Actuarial (gains) losses	$ (1)	(19)
Transfers of benefit obligation		(48)
Plan amendments		(77)
Benefits paid	$ (47)	(44)
Obligation at measurement date	354	379	533
Change in Fair Value of Plan Assets [Rollforward]
Actual return on plan assets	1
Benefits paid	(47)	(44)
Employer contributions	39	36
Plan participants' contributions	7	8
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	207	233
Service cost	1	1	9
Interest cost on projected benefit obligation	8	11	22
Plan participants' contributions	4	4
Actuarial (gains) losses	$ (13)	(21)
Transfers of benefit obligation		$ (2)
Plan amendments
Benefits paid	$ (19)	$ (19)
Obligation at measurement date	188	207	233
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	(1)
Actual return on plan assets	1
Benefits paid	(19)	(19)
Employer contributions	15	14
Plan participants' contributions	4	4
Plan assets at measurement date		(1)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	170	253
Service cost	1	3	7
Interest cost on projected benefit obligation	7	12	16
Plan participants' contributions	3	4
Actuarial (gains) losses	11
Plan amendments		(78)
Benefits paid	(28)	(24)
Obligation at measurement date	164	170	253
Change in Fair Value of Plan Assets [Rollforward]
Actual return on plan assets	1
Benefits paid	(28)	(24)
Employer contributions	25	20
Plan participants' contributions	3	4
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	39	42
Service cost			1
Interest cost on projected benefit obligation	2	2	2
Plan participants' contributions	1
Actuarial (gains) losses	(3)
Transfers of benefit obligation		(1)
Plan amendments	(1)	(1)
Benefits paid	(3)	(3)
Obligation at measurement date	35	39	42
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	8	8
Benefits paid	(3)	(3)
Employer contributions	2	3
Plan participants' contributions	1
Plan assets at measurement date	8	8	8
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Change in Projected Benefit Obligation [Rollforward]
Obligation at prior measurement date	96	118
Service cost	1	1	1
Interest cost on projected benefit obligation	4	5	5
Plan participants' contributions	2	2
Actuarial (gains) losses	1	(20)
Plan amendments	(4)
Benefits paid	(13)	(10)
Obligation at measurement date	87	96	118
Change in Fair Value of Plan Assets [Rollforward]
Plan assets at prior measurement date	23	18
Actual return on plan assets	(1)	2
Benefits paid	(13)	(10)
Employer contributions	8	11
Plan participants' contributions	2	2
Plan assets at measurement date	$ 19	$ 23	$ 18