Employee Benefit Plans (Amounts Recognized in Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	$ 1,103	$ 1,111
Regulatory assets	13,879	13,901
Regulatory Liabilities	15,732	7,290
Duke Energy Carolinas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	95	97
Regulatory assets	3,152	3,397
Regulatory Liabilities	6,357	3,001
Progress Energy [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	545	547
Regulatory assets	6,751	6,123
Regulatory Liabilities	5,519	2,584
Duke Energy Progress [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	248	252
Regulatory assets	3,859	3,431
Regulatory Liabilities	4,138	2,104
Duke Energy Florida [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	264	262
Regulatory assets	2,892	2,693
Regulatory Liabilities	1,381	479
Duke Energy Ohio [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	59	56
Regulatory assets	494	557
Regulatory Liabilities	927	257
Duke Energy Indiana [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	76	71
Regulatory assets	1,143	1,222
Regulatory Liabilities	1,747	788
Piedmont Natural Gas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	5	14
Regulatory assets	378	497
Regulatory Liabilities	1,144	608
Pension Plan [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	680	518
Noncurrent pension liability	125	118
Net amount recognized	555	400
Regulatory assets	1,886	2,098
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(41)	(41)
Prior year service cost (credit) arising during the year	(5)	(6)
Net actuarial loss (gain)	116	123
Net amount recognized in accumulated other comprehensive income (loss)	70	76
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	132	147
Unrecognized prior service (credit) cost	(32)	(24)
Pension Plan [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	23	28
Noncurrent pension liability	308	304
Total accrued pension liability	331	332
Regulatory assets	78	73
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(4)	(3)
Prior year service cost (credit) arising during the year	(1)	(1)
Net actuarial loss (gain)	12	10
Net amount recognized in accumulated other comprehensive income (loss)	7	6
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	8	7
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	343	273
Net amount recognized	343	273
Regulatory assets	406	476
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	29	31
Unrecognized prior service (credit) cost	(8)	(8)
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	2	2
Noncurrent pension liability	12	12
Total accrued pension liability	14	14
Regulatory assets	4	5
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	245	225
Noncurrent pension liability	68	62
Net amount recognized	177	163
Regulatory assets	756	805
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(3)	(6)
Net actuarial loss (gain)	9	16
Net amount recognized in accumulated other comprehensive income (loss)	6	10
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	44	52
Unrecognized prior service (credit) cost	(3)	(3)
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	8	8
Noncurrent pension liability	108	106
Total accrued pension liability	116	114
Regulatory assets	21	18
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax asset	(3)	(3)
Net actuarial loss (gain)	9	9
Net amount recognized in accumulated other comprehensive income (loss)	6	6
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	2	2
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	155	132
Net amount recognized	155	132
Regulatory assets	341	378
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	21	23
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	3	2
Noncurrent pension liability	32	31
Total accrued pension liability	35	33
Regulatory assets	8	7
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	1
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	87	91
Noncurrent pension liability	68	62
Net amount recognized	19	29
Regulatory assets	415	426
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	23	29
Unrecognized prior service (credit) cost	(1)	(1)
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	3	3
Noncurrent pension liability	44	43
Total accrued pension liability	47	46
Regulatory assets	13	11
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	1
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	8	6
Noncurrent pension liability	29	25
Net amount recognized	(21)	(19)
Regulatory assets	90	81
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	5	5
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	4	4
Total accrued pension liability	4	4
Regulatory assets	1	1
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	16
Noncurrent pension liability	1	1
Net amount recognized	15	(1)
Regulatory assets	152	171
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	7	8
Unrecognized prior service (credit) cost	(2)	(2)
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	3	3
Total accrued pension liability	3	3
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Prefunded pension	55	3
Net amount recognized	55	3
Regulatory assets	73	137
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	11	13
Unrecognized prior service (credit) cost	(9)	(2)
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	4	4
Total accrued pension liability	4	4
Regulatory assets	1	1
Other Post-Retirement Benefit Plans [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	36	38
Noncurrent pension liability	552	586
Total accrued pension liability	588	624
Regulatory assets	125	54
Regulatory Liabilities	147	174
Accumulated Other Comprehensive Income (Loss) [Abstract]
Deferred income tax liability	4	5
Prior year service cost (credit) arising during the year	(2)	(5)
Net actuarial loss (gain)	(10)	(10)
Net amount recognized in accumulated other comprehensive income (loss)	(8)	(10)
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	5	10
Unrecognized prior service (credit) cost	(19)	(115)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	56	64
Total accrued pension liability	56	64
Regulatory Liabilities	44	46
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	3	(2)
Unrecognized prior service (credit) cost	(5)	(10)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	29	31
Noncurrent pension liability	313	325
Total accrued pension liability	342	356
Regulatory assets	129	48
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	21
Unrecognized prior service (credit) cost	(7)	(85)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	15	17
Noncurrent pension liability	169	174
Total accrued pension liability	184	191
Regulatory assets	80	38
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		12
Unrecognized prior service (credit) cost	(1)	(55)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	14	15
Noncurrent pension liability	142	149
Total accrued pension liability	156	164
Regulatory assets	49	10
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss	1	9
Unrecognized prior service (credit) cost	(6)	(30)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Current pension liability	2	2
Noncurrent pension liability	21	23
Total accrued pension liability	23	25
Regulatory Liabilities	16	19
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		(2)
Unrecognized prior service (credit) cost	(1)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	67	63
Total accrued pension liability	67	63
Regulatory assets	46	51
Regulatory Liabilities	64	71
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized net actuarial loss		(6)
Unrecognized prior service (credit) cost	(1)	(1)
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Noncurrent pension liability	1	10
Total accrued pension liability	1	10
Regulatory assets	(4)	$ 7
Amounts to be recognized in net periodic pension expense in the next year [Abstract]
Unrecognized prior service (credit) cost	$ (2)