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Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 USD ($) | Jun. 30, 2018 USD ($)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | $ 2,272 | $ 2,272
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt Securities, Available-for-sale, Realized Gain | 5 | 10
Debt Securities, Available-for-sale, Realized Loss | 12 | 25
Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 2,136 | 2,136
Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 267 | 267
Corporate Debt Securities [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 5 | 5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 12 | 12
Debt Securities, Available-for-sale | 560 | 560
Corporate Debt Securities [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 68 | 68
Municipal Bonds [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 2 | 2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 4 | 4
Debt Securities, Available-for-sale | 341 | 341
Municipal Bonds [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 87 | 87
US Treasury and Government [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 7 | 7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 20 | 20
Debt Securities, Available-for-sale | 991 | 991
US Treasury and Government [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 52 | 52
Other Debt Obligations [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 3
Debt Securities, Available-for-sale | 128 | 128
Other Debt Obligations [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 45 | 45
Duke Energy Carolinas [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1,017 | 1,017
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt Securities, Available-for-sale, Realized Gain | 4 | 9
Debt Securities, Available-for-sale, Realized Loss | 8 | 18
Duke Energy Carolinas [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1,049 | 1,049
Duke Energy Carolinas [Member] | Corporate Debt Securities [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 2 | 2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 8 | 8
Debt Securities, Available-for-sale | 347 | 347
Duke Energy Carolinas [Member] | Municipal Bonds [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 72 | 72
Duke Energy Carolinas [Member] | US Treasury and Government [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 2 | 2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 12 | 12
Debt Securities, Available-for-sale | 474 | 474
Duke Energy Carolinas [Member] | Other Debt Obligations [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 3
Debt Securities, Available-for-sale | 124 | 124
Progress Energy [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1,050 | 1,050
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt Securities, Available-for-sale, Realized Gain | 1 | 1
Debt Securities, Available-for-sale, Realized Loss | 4 | 7
Progress Energy [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1,087 | 1,087
Progress Energy [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 58 | 58
Progress Energy [Member] | Corporate Debt Securities [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 3 | 3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 4 | 4
Debt Securities, Available-for-sale | 213 | 213
Progress Energy [Member] | Municipal Bonds [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 3
Debt Securities, Available-for-sale | 269 | 269
Progress Energy [Member] | Municipal Bonds [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale | 47 | 47
Progress Energy [Member] | US Treasury and Government [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 5 | 5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 8 | 8
Debt Securities, Available-for-sale | 517 | 517
Progress Energy [Member] | Other Debt Obligations [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 4 | 4
Duke Energy Progress [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 762 | 762
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt Securities, Available-for-sale, Realized Gain | 1 | 1
Debt Securities, Available-for-sale, Realized Loss | 3 | 5
Duke Energy Progress [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 808 | 808
Duke Energy Progress [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1 | 1
Duke Energy Progress [Member] | Corporate Debt Securities [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 2 | 2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 3
Debt Securities, Available-for-sale | 153 | 153
Duke Energy Progress [Member] | Municipal Bonds [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 3
Debt Securities, Available-for-sale | 268 | 268
Duke Energy Progress [Member] | US Treasury and Government [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 4 | 4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 6 | 6
Debt Securities, Available-for-sale | 339 | 339
Duke Energy Progress [Member] | Other Debt Obligations [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 2 | 2
Duke Energy Florida [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 288 | 288
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt Securities, Available-for-sale, Realized Loss | 1 | 2
Duke Energy Florida [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 279 | 279
Duke Energy Florida [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 48 | 48
Duke Energy Florida [Member] | Corporate Debt Securities [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | 60 | 60
Duke Energy Florida [Member] | Municipal Bonds [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 1 | 1
Duke Energy Florida [Member] | Municipal Bonds [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale | 47 | 47
Duke Energy Florida [Member] | US Treasury and Government [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 2 | 2
Debt Securities, Available-for-sale | 178 | 178
Duke Energy Florida [Member] | Other Debt Obligations [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 2 | 2
Duke Energy Indiana [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 41 | 41
Duke Energy Indiana [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 41 | 41
Duke Energy Indiana [Member] | Corporate Debt Securities [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale | 8 | 8
Duke Energy Indiana [Member] | Municipal Bonds [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 1
Debt Securities, Available-for-sale | $ 33 | $ 33

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