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Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 USD ($) | Sep. 30, 2018 USD ($)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | $ 2,307 | $ 2,307
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt securities, available-for-sale, realized gain | 4 | 14
Debt securities, available-for-sale, realized loss | 7 | 32
Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 2,131 | 2,131
Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 272 | 272
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 | 10 | 10
Debt securities, available-for-sale | 595 | 595
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 | 64 | 64
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 | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 7 | 7
Debt securities, available-for-sale | 346 | 346
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 | 85 | 85
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 | 25 | 25
Debt securities, available-for-sale | 974 | 974
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 | 59 | 59
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 | 141 | 141
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 | 43 | 43
Duke Energy Carolinas [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 1,028 | 1,028
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt securities, available-for-sale, realized gain | 4 | 13
Debt securities, available-for-sale, realized loss | 6 | 24
Duke Energy Carolinas [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 1,046 | 1,046
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 | 7 | 7
Debt securities, available-for-sale | 372 | 372
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 | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 2 | 2
Debt securities, available-for-sale | 80 | 80
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 | 1 | 1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 14 | 14
Debt securities, available-for-sale | 439 | 439
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 gain, before tax | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 3 | 3
Debt securities, available-for-sale | 137 | 137
Progress Energy [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 1,076 | 1,076
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt securities, available-for-sale, realized gain | 0 | 1
Debt securities, available-for-sale, realized loss | 1 | 8
Progress Energy [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 1,085 | 1,085
Progress Energy [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 66 | 66
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 | 3 | 3
Debt securities, available-for-sale | 223 | 223
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 | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 5 | 5
Debt securities, available-for-sale | 266 | 266
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 | 48 | 48
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 | 4 | 4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 11 | 11
Debt securities, available-for-sale | 535 | 535
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 | 781 | 781
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt securities, available-for-sale, realized gain | 0 | 1
Debt securities, available-for-sale, realized loss | 1 | 6
Duke Energy Progress [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract] |  |
Debt securities, available-for-sale | 823 | 823
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 | 8 | 8
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 | 2 | 2
Debt securities, available-for-sale | 162 | 162
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 | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 5 | 5
Debt securities, available-for-sale | 265 | 265
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 | 3 | 3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 8 | 8
Debt securities, available-for-sale | 352 | 352
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, accumulated gross unrealized gain, before tax | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 0
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 | 295 | 295
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |
Debt securities, available-for-sale, realized loss | 0 | 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 | 262 | 262
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 | 61 | 61
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, accumulated gross unrealized gain, before tax | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 0
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 | 48 | 48
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 | 3 | 3
Debt securities, available-for-sale | 183 | 183
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, accumulated gross unrealized gain, before tax | 0 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 0
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 | 40 | 40
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 | 40 | 40
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 | $ 32 | $ 32

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