Employee Benefit Plans (Expected Benefit Payments) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	$ 642
2019	644
2020	661
2021	666
2022	672
2023-2027	3,099
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	23
2019	21
2020	21
2021	22
2022	25
2023-2027	117
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	185
2019	185
2020	195
2021	194
2022	197
2023-2027	865
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	2
2019	1
2020	1
2021	1
2022	1
2023-2027	6
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	161
2019	164
2020	172
2021	175
2022	176
2023-2027	888
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	8
2019	8
2020	8
2021	8
2022	8
2023-2027	36
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	85
2019	86
2020	90
2021	93
2022	92
2023-2027	449
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	3
2019	2
2020	2
2021	2
2022	2
2023-2027	11
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	75
2019	77
2020	80
2021	81
2022	83
2023-2027	435
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	3
2019	3
2020	3
2021	3
2022	3
2023-2027	15
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	36
2019	36
2020	36
2021	37
2022	36
2023-2027	166
Pension Plan [Member] | Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	1
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	47
2019	46
2020	44
2021	44
2022	44
2023-2027	210
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	1
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	29
2019	26
2020	24
2021	24
2022	23
2023-2027	103
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023-2027	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	78
2019	76
2020	73
2021	71
2022	68
2023-2027	290
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	17
2019	17
2020	17
2021	17
2022	17
2023-2027	70
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	30
2019	29
2020	29
2021	28
2022	27
2023-2027	117
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	16
2019	15
2020	15
2021	15
2022	14
2023-2027	63
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	14
2019	14
2020	14
2021	13
2022	13
2023-2027	54
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	3
2019	3
2020	3
2021	3
2022	3
2023-2027	12
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	9
2019	9
2020	8
2021	7
2022	7
2023-2027	29
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2018	2
2019	2
2020	2
2021	3
2022	3
2023-2027	$ 13