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Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI, realized gain | $ 66 | $ 47 | $ 101 | $ 66 |
Equity securities, FV-NI, realized loss | 63 | 31 | 93 | 44 |
Ndtf [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 3,076 |  | 3,076 |  | $ 2,402
Equity Securities, FV-NI, Accumulated Unrealized Loss | 36 |  | 36 |  | 95
Equity securities, FV-NI | 5,178 |  | 5,178 |  | 4,475
Other Classification [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 49 |  | 49 |  | 36
Equity Securities, FV-NI, Accumulated Unrealized Loss |  |  |  |  | 1
Equity securities, FV-NI | 112 |  | 112 |  | 99
Duke Energy Carolinas [Member] |  |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI, realized gain | 44 | 26 | 67 | 36 |
Equity securities, FV-NI, realized loss | 48 | 17 | 69 | 22 |
Duke Energy Carolinas [Member] | Ndtf [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,671 |  | 1,671 |  | 1,309
Equity Securities, FV-NI, Accumulated Unrealized Loss | 9 |  | 9 |  | 54
Equity securities, FV-NI | 2,883 |  | 2,883 |  | 2,484
Progress Energy [Member] |  |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI, realized gain | 22 | 21 | 34 | 30 |
Equity securities, FV-NI, realized loss | 15 | 14 | 24 | 22 |
Progress Energy [Member] | Ndtf [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,405 |  | 1,405 |  | 1,093
Equity Securities, FV-NI, Accumulated Unrealized Loss | 27 |  | 27 |  | 41
Equity securities, FV-NI | 2,295 |  | 2,295 |  | 1,991
Duke Energy Progress [Member] |  |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI, realized gain | 7 | 17 | 17 | 25 |
Equity securities, FV-NI, realized loss | 7 | 12 | 15 | 20 |
Duke Energy Progress [Member] | Ndtf [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,092 |  | 1,092 |  | 833
Equity Securities, FV-NI, Accumulated Unrealized Loss | 24 |  | 24 |  | 30
Equity securities, FV-NI | 1,886 |  | 1,886 |  | 1,588
Duke Energy Florida [Member] |  |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI, realized gain | 15 | 4 | 17 | 5 |
Equity securities, FV-NI, realized loss | 8 | $ 2 | 9 | $ 2 |
Duke Energy Florida [Member] | Ndtf [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 313 |  | 313 |  | 260
Equity Securities, FV-NI, Accumulated Unrealized Loss | 3 |  | 3 |  | 11
Equity securities, FV-NI | 409 |  | 409 |  | 403
Duke Energy Indiana [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 37 |  | 37 |  | 29
Equity securities, FV-NI | 74 |  | 74 |  | 67
Duke Energy Indiana [Member] | Other Classification [Member] |  |  |  |  |
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract] |  |  |  |  |
Equity securities, FV-NI | $ 74 |  | $ 74 |  | $ 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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- Definition Amount of realized gain from sale 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 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714 + Details
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