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Employee Benefit Plans (Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions | 2 Months Ended | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 31, 2016
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | $ 6 | $ (3) | $ 11 |
Progress Energy [Member] |  |  |  |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | (5) | (4) | $ (1) |
Pension Plan [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 298 | (212) |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  | (2) |  |  |
Prior year service cost (credit) arising during the year |  | 1 | 1 |  |
Amortization of prior year actuarial gains (losses) |  | 10 | (7) |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | 9 | (6) |  |
Pension Plan [Member] | Nonqualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | (16) | 5 |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  | 1 |  |  |
Actuarial (gains) losses arising during the year |  | (4) | 2 |  |
Prior year service cost (credit) arising during the year |  |  | (1) |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | (3) | 1 |  |
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 170 | (70) |  |
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 1 | (1) |  |
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 40 | (49) |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  | 1 | 3 |  |
Amortization of prior year actuarial gains (losses) |  | (4) | (7) |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | (3) | (4) |  |
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | (6) | 3 |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  | 1 |  |  |
Actuarial (gains) losses arising during the year |  | (3) |  |  |
Net amount recognized in accumulated other comprehensive (income) loss |  | (2) |  |  |
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 31 | (37) |  |
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | (3) | 1 |  |
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 9 | (11) |  |
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | (3) | 2 |  |
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 10 | 9 |  |
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 30 | (19) |  |
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) | $ 34 | 8 | (64) |  | $ 35
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  |  | 0 |  |
Prior year service cost (credit) arising during the year |  |  | 0 |  |
Amortization of prior year actuarial gains (losses) |  |  | 0 |  |
Net amount recognized in accumulated other comprehensive (income) loss |  |  | 0 |  |
Other Post-Retirement Benefit Plans [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 137 | 71 |  |
Regulatory liabilities, net increase (decrease) |  | 154 | (27) |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  | (1) | (1) |  |
Amortization of prior year prior service cost |  | 1 | 3 |  |
Net amount recognized in accumulated other comprehensive (income) loss |  |  | 2 |  |
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory liabilities, net increase (decrease) |  | (6) | (2) |  |
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 133 | 81 |  |
Regulatory liabilities, net increase (decrease) |  | 149 |  |  |
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 84 | 42 |  |
Regulatory liabilities, net increase (decrease) |  | 93 |  |  |
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | 49 | 39 |  |
Regulatory liabilities, net increase (decrease) |  | 56 |  |  |
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory liabilities, net increase (decrease) |  | 2 | (3) |  |
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) |  | (5) | (5) |  |
Regulatory liabilities, net increase (decrease) |  | 3 | (7) |  |
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member] |  |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |  |
Regulatory assets, net increase (decrease) | $ (1) | $ 4 | (11) |  | $ 2
Regulatory liabilities, net increase (decrease) |  |  | 0 |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |  |
Deferred income tax expense (benefit) |  |  | 0 |  |
Amortization of prior year prior service cost |  |  | 0 |  |
Net amount recognized in accumulated other comprehensive (income) loss |  |  | $ 0 |  |

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