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Employee Benefit Plans (Fair Value Measurements of Plan Assets - Master Retirement Trust) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 27 | $ 28 | $ 38
Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 8,324 | 9,114 |
Master Trust [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 2,052 | 2,189 |
Master Trust [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 5,133 | 5,552 |
Master Trust [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 27 | 28 |
Master Trust [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1,112 | 1,345 |
Master Trust [Member] | Equity Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 2,373 | 2,823 |
Master Trust [Member] | Equity Securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1,751 | 1,976 |
Master Trust [Member] | Equity Securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 622 | 847 |
Master Trust [Member] | Corporate Debt Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 4,054 | 4,694 |
Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 4,054 | 4,694 |
Master Trust [Member] | Short Term Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 363 | 246 |
Master Trust [Member] | Short Term Investments [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 279 | 192 |
Master Trust [Member] | Short Term Investments [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 84 | 54 |
Master Trust [Member] | Partnership Interest [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 120 | 137 |
Master Trust [Member] | Partnership Interest [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 120 | 137 |
Master Trust [Member] | Hedge Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 226 | 226 |
Master Trust [Member] | Hedge Funds [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 226 | 226 |
Master Trust [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 144 | 135 |
Master Trust [Member] | Real Estate [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 144 | 135 |
Master Trust [Member] | US Treasury and Government [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 961 | 762 |
Master Trust [Member] | US Treasury and Government [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 961 | 762 |
Master Trust [Member] | Guaranteed Investment Contracts [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 27 | 28 |
Master Trust [Member] | Guaranteed Investment Contracts [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 27 | 28 |
Master Trust [Member] | Government Bonds - Foreign [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 30 | 38 |
Master Trust [Member] | Government Bonds - Foreign [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 30 | 38 |
Master Trust [Member] | Cash [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 28 | 6 |
Master Trust [Member] | Cash [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 28 | 6 |
Master Trust [Member] | Asset Backed Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 2 |
Master Trust [Member] | Asset Backed Securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  | 2 |
Master Trust [Member] | Miscellaneous Investments And Other [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | (2) | 17 |
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | (6) | 15 |
Master Trust [Member] | Miscellaneous Investments And Other [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 4 | 2 |
OPEB [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 49 | 58 |
OPEB [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 49 | 58 |
OPEB [Member] | Equity Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 25 | 28 |
OPEB [Member] | Equity Securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 25 | 28 |
OPEB [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1 | 1 |
OPEB [Member] | Real Estate [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 1 | 1 |
OPEB [Member] | Cash and Cash Equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3 | 8 |
OPEB [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 3 | 8 |
OPEB [Member] | Debt Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | 20 | 21 |
OPEB [Member] | Debt Securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets | $ 20 | $ 21 |
Duke Energy Carolinas [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 27.00% | 27.00% |
Progress Energy [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 31.00% | 30.00% |
Duke Energy Progress [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 15.00% | 15.00% |
Duke Energy Florida [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 16.00% | 15.00% |
Duke Energy Ohio [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 5.00% | 5.00% |
Duke Energy Indiana [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 7.00% | 8.00% |
Piedmont Natural Gas [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets |  |  | $ 9
Piedmont Natural Gas [Member] | Master Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Allocated assets | 4.00% | 4.00% |

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