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Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 31, 2016 | Oct. 31, 2015
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | $ 81 | $ 98 | $ 94 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 81 | 98 | 94 |  |
Provision/adjustments | 26 | 8 | 19 |  |
Cash reductions | (30) | (25) | (15) |  |
Ending balance | 77 | 81 | 98 |  |
Duke Energy Carolinas [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 10 | 10 | 10 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 10 | 10 | 10 |  |
Provision/adjustments | 3 | 3 | 4 |  |
Cash reductions | (2) | (3) | (4) |  |
Ending balance | 11 | 10 | 10 |  |
Progress Energy [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 15 | 18 | 17 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 15 | 18 | 17 |  |
Provision/adjustments | 2 | 3 | 7 |  |
Cash reductions | (6) | (6) | (6) |  |
Ending balance | 11 | 15 | 18 |  |
Duke Energy Progress [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 3 | 3 | 3 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 3 | 3 | 3 |  |
Provision/adjustments | 3 | 2 | 2 |  |
Cash reductions | (2) | (2) | (2) |  |
Ending balance | 4 | 3 | 3 |  |
Duke Energy Florida [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 12 | 14 | 14 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 12 | 14 | 14 |  |
Provision/adjustments | (2) | 2 | 4 |  |
Cash reductions | (4) | (4) | (4) |  |
Ending balance | 6 | 12 | 14 |  |
Duke Energy Ohio [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 47 | 59 | 54 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 47 | 59 | 54 |  |
Provision/adjustments | 21 | 3 | 7 |  |
Cash reductions | (20) | (15) | (2) |  |
Ending balance | 48 | 47 | 59 |  |
Duke Energy Indiana [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 5 | 10 | 12 |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 5 | 10 | 12 |  |
Provision/adjustments | 1 | (4) | 1 |  |
Cash reductions | (1) | (1) | (3) |  |
Ending balance | 5 | 5 | 10 |  |
Piedmont Natural Gas [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental reserve | 2 | 1 | 1 | $ 1 | $ 1
Accrual for Environmental Loss Contingencies [Roll Forward] |  |  |  |  |
Beginning balance | 2 | 1 |  |  |
Ending balance | 2 | $ 2 | $ 1 |  |
Environmental Reserves [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental Exit Costs, Reasonably Possible Additional Loss | 46 |  |  |  |
Environmental Reserves [Member] | Duke Energy Carolinas [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental Exit Costs, Reasonably Possible Additional Loss | 17 |  |  |  |
Environmental Reserves [Member] | Duke Energy Ohio [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental Exit Costs, Reasonably Possible Additional Loss | 19 |  |  |  |
Environmental Reserves [Member] | Piedmont Natural Gas [Member] |  |  |  |  |
Disclosure Environmental Matters Details [Line Items] |  |  |  |  |
Environmental Exit Costs, Reasonably Possible Additional Loss | $ 2 |  |  |  |

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