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Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 11 | $ 27 | $ 28
Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 9,025 | 8,324 |
Master Trust | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,199 | 2,052 |
Master Trust | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 5,487 | 5,133 |
Master Trust | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 11 | 27 |
Master Trust | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 328 | 1,112 |
Master Trust | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 2,730 | 2,373 |
Master Trust | Equity securities | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 2,712 | 1,751 |
Master Trust | Equity securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Equity securities | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Equity securities | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 18 | 622 |
Master Trust | Corporate debt securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,999 | 4,054 |
Master Trust | Corporate debt securities | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Corporate debt securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,999 | 4,054 |
Master Trust | Corporate debt securities | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Corporate debt securities | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Short-term investment funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 545 | 363 |
Master Trust | Short-term investment funds | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 455 | 279 |
Master Trust | Short-term investment funds | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 90 | 84 |
Master Trust | Short-term investment funds | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Short-term investment funds | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Partnership interests |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 104 | 120 |
Master Trust | Partnership interests | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Partnership interests | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Partnership interests | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Partnership interests | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 104 | 120 |
Master Trust | Hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 206 | 226 |
Master Trust | Hedge funds | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Hedge funds | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Hedge funds | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Hedge funds | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 206 | 226 |
Master Trust | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 144 |
Master Trust | Real estate | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Real estate | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Real estate | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Real estate | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 144 |
Master Trust | U.S. government bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1,231 | 961 |
Master Trust | U.S. government bonds | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | U.S. government bonds | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1,231 | 961 |
Master Trust | U.S. government bonds | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | U.S. government bonds | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Guaranteed investment contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 11 | 27 |
Master Trust | Guaranteed investment contracts | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Guaranteed investment contracts | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Guaranteed investment contracts | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 11 | 27 |
Master Trust | Guaranteed investment contracts | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Governments bonds – foreign |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 78 | 30 |
Master Trust | Governments bonds – foreign | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Governments bonds – foreign | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 78 | 30 |
Master Trust | Governments bonds – foreign | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Governments bonds – foreign | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Cash |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 75 | 28 |
Master Trust | Cash | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 75 | 28 |
Master Trust | Cash | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Cash | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Cash | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Net pending transactions and other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 46 | (2) |
Master Trust | Net pending transactions and other investments | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | (43) | (6) |
Master Trust | Net pending transactions and other investments | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 89 | 4 |
Master Trust | Net pending transactions and other investments | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
Master Trust | Net pending transactions and other investments | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 0 |
OPEB |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 50 | 49 |
OPEB | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 50 | 49 |
OPEB | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 22 | 25 |
OPEB | Equity securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 22 | 25 |
OPEB | Real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1 | 1 |
OPEB | Real estate | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1 | 1 |
OPEB | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 9 | 3 |
OPEB | Cash and cash equivalents | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 9 | 3 |
OPEB | Debt securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 18 | 20 |
OPEB | Debt securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 18 | $ 20 |
Duke Energy Carolinas | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 26.00% | 27.00% |
Progress Energy | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 31.00% | 31.00% |
Duke Energy Progress | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 15.00% | 15.00% |
Duke Energy Florida | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 17.00% | 16.00% |
Duke Energy Ohio | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 5.00% | 5.00% |
Duke Energy Indiana | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 7.00% | 7.00% |
Piedmont | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 4.00% | 4.00% |

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