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Commitments and Contingencies (Narrative) (Details) | 1 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jul. 31, 2018 USD ($) | Sep. 30, 2018 USD ($) plant claim T | Dec. 31, 2017 USD ($)
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | $ 63,000,000 | $ 88,000,000
Coal Ash Insurance Coverage Litigation [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Number of NC and SC plants with ash basins | plant |  | 15 |
NCDEQ State Enforcement Actions [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Number of plants with no disputed facts | plant |  | 7 |
Number of NC plants with ash basins | plant |  | 14 |
Number of plants with disputed facts | plant |  | 7 |
Groundwater Contamination Claims [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Goodwill payment |  | $ 5,000 |
Water bill stipend period |  | 25 years |
Duke Energy Carolinas [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | $ 11,000,000 | 30,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | 4,000,000 |
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Asbestos-related injuries and damages reserves |  | 461,000,000 | 489,000,000
Reinsurance retention policy, excess retention, amount reinsured |  | 764,000,000 |
Probable insurance recoveries |  | $ 553,000,000 | 585,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Non-Malignant Asbestos Claim [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency, pending claims, number | claim |  | 160 |
Asbestos-related injuries and damages reserves |  | $ 43,000,000 |
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Malignant Asbestos Claim [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency, pending claims, number | claim |  | 63 |
Asbestos-related injuries and damages reserves |  | $ 19,000,000 |
Progress Energy [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | 50,000,000 | 55,000,000
Duke Energy Progress [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | 11,000,000 | 13,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | 2,000,000 |
Duke Energy Progress [Member] | Spent Nuclear Fuels [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Gain contingency, unrecorded amount |  |  | 48,000,000
Litigation settlement, amount awarded from other party |  | $ 48,000,000 |
Duke Energy Progress [Member] | Gypsum Supply Agreements [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Minimum amount of gypsum to be supplied | T |  | 50,000 |
Estimate of possible losses |  | $ 90,000,000 |
Duke Energy Florida [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Loss contingency accrual |  | 23,000,000 | 24,000,000
Duke Energy Florida [Member] | Spent Nuclear Fuels [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Gain contingency, unrecorded amount |  |  | $ 25,000,000
Litigation settlement, amount awarded from other party |  | 21,000,000 |
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Gain contingency, unrecorded amount |  | 54,000,000 |
Loss contingency, damages sought, original amount |  | 510,000,000 |
Loss contingency, damages awarded, value |  | 30,000,000 |
Gain contingency, dismissed amount |  | 54,000,000 |
Loss contingency damages awarded and interest, value |  | 34,000,000 |
Loss contingency, damages paid, value | $ 34,000,000 |  |
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member] |  |  |
Valuation and Qualifying Accounts [Abstract] |  |  |
Gain contingency, unrecorded amount |  | $ 43,000,000 |

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