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

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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