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Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI, realized gain | $ 35 | $ 19 |
Equity securities, FV-NI, realized loss | 30 | 13 |
Ndtf [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 2,923 |  | $ 2,402
Equity Securities, FV-NI, Accumulated Unrealized Loss | 65 |  | 95
Equity securities, FV-NI | 5,061 |  | 4,475
Other Classification [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 47 |  | 36
Equity Securities, FV-NI, Accumulated Unrealized Loss |  |  | 1
Equity securities, FV-NI | 112 |  | 99
Duke Energy Carolinas [Member] |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI, realized gain | 23 | 10 |
Equity securities, FV-NI, realized loss | 21 | 5 |
Duke Energy Carolinas [Member] | Ndtf [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,593 |  | 1,309
Equity Securities, FV-NI, Accumulated Unrealized Loss | 37 |  | 54
Equity securities, FV-NI | 2,791 |  | 2,484
Progress Energy [Member] |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI, realized gain | 12 | 9 |
Equity securities, FV-NI, realized loss | 9 | 8 |
Progress Energy [Member] | Ndtf [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,330 |  | 1,093
Equity Securities, FV-NI, Accumulated Unrealized Loss | 28 |  | 41
Equity securities, FV-NI | 2,270 |  | 1,991
Duke Energy Progress [Member] |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI, realized gain | 10 | 8 |
Equity securities, FV-NI, realized loss | 8 | 8 |
Duke Energy Progress [Member] | Ndtf [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,022 |  | 833
Equity Securities, FV-NI, Accumulated Unrealized Loss | 20 |  | 30
Equity securities, FV-NI | 1,812 |  | 1,588
Duke Energy Florida [Member] |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI, realized gain | 2 | 1 |
Equity securities, FV-NI, realized loss | 1 | $ 0 |
Duke Energy Florida [Member] | Ndtf [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 308 |  | 260
Equity Securities, FV-NI, Accumulated Unrealized Loss | 8 |  | 11
Equity securities, FV-NI | 458 |  | 403
Duke Energy Indiana [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 37 |  | 29
Equity securities, FV-NI | 76 |  | 67
Duke Energy Indiana [Member] | Other Classification [Member] |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |
Equity securities, FV-NI | $ 76 |  | $ 67

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- Definition Amount of accumulated unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Substantially all of the associated unrealized gains and losses on these investments are deferred as a regulatory asset or liability. + References No definition available. + Details
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- Definition Amount of accumulated unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Substantially all of the associated unrealized gains and losses on these investments are deferred as a regulatory asset or liability. + References No definition available. + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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