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Employee Benefit Plans (Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Net amount recognized in accumulated other comprehensive income | [1] | $ (9) | $ 6 | $ (3)
Progress Energy |  |  |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Net amount recognized in accumulated other comprehensive income |  | (2) | (5) | $ (4)
Pension Plan | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (212) | 298 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 20 | (2) |
Amortization of prior year service credit |  | 1 | 1 |
Amortization of prior year actuarial losses |  | (15) | 10 |
Net amount recognized in accumulated other comprehensive income |  | 6 | 9 |
Pension Plan | Duke Energy Carolinas | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (156) | 170 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Pension Plan | Progress Energy | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (79) | 40 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 1 | 1 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | (2) | (4) |
Net amount recognized in accumulated other comprehensive income |  | (1) | (3) |
Pension Plan | Duke Energy Progress | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (59) | 31 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Pension Plan | Duke Energy Florida | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (20) | 9 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | (1) | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 3 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 2 | 0 |
Pension Plan | Duke Energy Ohio | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 12 | 10 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Pension Plan | Duke Energy Indiana | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 22 | 30 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Pension Plan | Piedmont | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 0 | 8 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year service credit |  | 0 | 0 |
Amortization of prior year actuarial losses |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (127) | 137 |
Accumulated other comprehensive loss (income) |  | (152) | 154 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | (1) |
Amortization of prior year prior service cost |  | (4) | 1 |
Net amount recognized in accumulated other comprehensive income |  | (4) | 0 |
Other Post-Retirement Benefit Plans | Duke Energy Carolinas |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 0 | 0 |
Accumulated other comprehensive loss (income) |  | 1 | (6) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Progress Energy |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (127) | 133 |
Accumulated other comprehensive loss (income) |  | (149) | 149 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Duke Energy Progress |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (82) | 84 |
Accumulated other comprehensive loss (income) |  | (93) | 93 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Duke Energy Florida |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (45) | 49 |
Accumulated other comprehensive loss (income) |  | (56) | 56 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Duke Energy Ohio |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 0 | 0 |
Accumulated other comprehensive loss (income) |  | (1) | 2 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Duke Energy Indiana |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (5) | (5) |
Accumulated other comprehensive loss (income) |  | (4) | 3 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | 0 | 0 |
Other Post-Retirement Benefit Plans | Piedmont |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 0 | 4 |
Accumulated other comprehensive loss (income) |  | 3 | 0 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year prior service cost |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | $ 0 | $ 0 |
[1] | Tax impacts are insignificant for all periods presented.

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