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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, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Net amount recognized in accumulated other comprehensive income | [1] | $ (6) | $ (9) | $ 6
Progress Energy |  |  |  |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Net amount recognized in accumulated other comprehensive income |  | 1 | (2) | $ (5)
Pension Plan | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (62) | (212) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 2 | 20 |
Amortization of prior year service credit |  | 1 | 1 |
Amortization of prior year actuarial losses |  | (11) | (15) |
Net amount recognized in accumulated other comprehensive income |  | (8) | 6 |
Pension Plan | Duke Energy Carolinas | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (39) | (156) |
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) |  | (26) | (79) |
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 |  | (1) | (2) |
Net amount recognized in accumulated other comprehensive income |  | 0 | (1) |
Pension Plan | Duke Energy Progress | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (30) | (59) |
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) |  | 4 | (20) |
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 |  | (3) | 3 |
Net amount recognized in accumulated other comprehensive income |  | (2) | 2 |
Pension Plan | Duke Energy Ohio | Qualified Plan |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | (2) | 12 |
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) |  | 5 | 22 |
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) |  | (1) | 0 |
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) |  | 9 | (127) |
Regulatory liabilities, net increase (decrease) |  | (10) | (152) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | (1) | 4 |
Net amount recognized in accumulated other comprehensive income |  | 1 | (4) |
Other Post-Retirement Benefit Plans | Duke Energy Carolinas |  |  |  |
Amounts Recognized in Regulatory Assets and Liabilities [Abstract] |  |  |  |
Regulatory assets, net increase (decrease) |  | 0 | 0 |
Regulatory liabilities, net increase (decrease) |  | (7) | 1 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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) |  | 9 | (127) |
Regulatory liabilities, net increase (decrease) |  | 0 | (149) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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) |  | 6 | (82) |
Regulatory liabilities, net increase (decrease) |  | 0 | (93) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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) |  | 3 | (45) |
Regulatory liabilities, net increase (decrease) |  | 0 | (56) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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 |
Regulatory liabilities, net increase (decrease) |  | 0 | (1) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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) |  | (4) | (5) |
Regulatory liabilities, net increase (decrease) |  | (1) | (4) |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 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 | 0 |
Regulatory liabilities, net increase (decrease) |  | 0 | 3 |
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) [Abstract] |  |  |  |
Deferred income tax expense (benefit) |  | 0 | 0 |
Amortization of prior year actuarial gain |  | 0 | 0 |
Net amount recognized in accumulated other comprehensive income |  | $ 0 | $ 0 |
[1] | Net of income tax impacts of approximately $35 million for the year ended December 31, 2020. Tax impacts are immaterial for other periods presented.

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