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Goodwill (Narrative) (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Sep. 30, 2018 | Dec. 31, 2017
Goodwill [Line Items] |  |
Goodwill | $ 19,303,000,000 | $ 19,396,000,000
Accumulated impairment charges | 122,000,000 | 29,000,000
Electric Utilities and Infrastructure [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 17,379,000,000 | 17,379,000,000
Gas Utilities and Infrastructure [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 1,924,000,000 | 1,924,000,000
Commercial Renewables [Member] |  |
Goodwill [Line Items] |  |
Goodwill |  | 93,000,000
Accumulated impairment charges | 122,000,000 | 29,000,000
Goodwill impairment | 93,000,000 |
Duke Energy Ohio [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 920,000,000 | 920,000,000
Accumulated impairment charges | 216,000,000 | 216,000,000
Duke Energy Ohio [Member] | Electric Utilities and Infrastructure [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 596,000,000 | 596,000,000
Duke Energy Ohio [Member] | Gas Utilities and Infrastructure [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 324,000,000 | 324,000,000
Progress Energy [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 3,655,000,000 | 3,655,000,000
Accumulated impairment charges | 0 | 0
Piedmont Natural Gas [Member] |  |
Goodwill [Line Items] |  |
Goodwill | 49,000,000 | 49,000,000
Accumulated impairment charges | $ 0 | $ 0

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