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Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 0 | $ 11 | $ 27
Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 9,479 | 9,025 |
Master Trust | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,541 | 3,199 |
Master Trust | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 5,603 | 5,487 |
Master Trust | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 0 | 11 |
Master Trust | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 335 | 328 |
Master Trust | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,202 | 2,730 |
Master Trust | Equity securities | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3,162 | 2,712 |
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 | 40 | 18 |
Master Trust | Corporate debt securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 4,162 | 3,999 |
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 | 4,162 | 3,999 |
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 | 397 | 545 |
Master Trust | Short-term investment funds | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 247 | 455 |
Master Trust | Short-term investment funds | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 150 | 90 |
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 | 97 | 104 |
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 | 97 | 104 |
Master Trust | Hedge funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 198 | 206 |
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 | 198 | 206 |
Master Trust | U.S. government bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1,164 | 1,231 |
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 | 1,164 | 1,231 |
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 |
Master Trust | Guaranteed investment contracts | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 0 |
Master Trust | Guaranteed investment contracts | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 0 |
Master Trust | Guaranteed investment contracts | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 11 |
Master Trust | Guaranteed investment contracts | Not Categorized |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 0 |
Master Trust | Governments bonds – foreign |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 73 | 78 |
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 | 73 | 78 |
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 | 98 | 75 |
Master Trust | Cash | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 98 | 75 |
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 | 88 | 46 |
Master Trust | Net pending transactions and other investments | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 34 | (43) |
Master Trust | Net pending transactions and other investments | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 54 | 89 |
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 | 48 | 50 |
OPEB | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 48 | 50 |
OPEB | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 23 | 22 |
OPEB | Equity securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 23 | 22 |
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 | 5 | 9 |
OPEB | Cash and cash equivalents | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 5 | 9 |
OPEB | Debt securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 19 | 18 |
OPEB | Debt securities | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 19 | $ 18 |
Duke Energy Carolinas | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 26.00% | 26.00% |
Progress Energy | Master Trust |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 32.00% | 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% | 17.00% |
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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