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Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($) $ in Millions | Mar. 31, 2019 | Dec. 31, 2018
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Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | $ 3,022 | $ 2,458
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 76 | 131
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 7,785 | 7,075
Debt securities, available-for-sale | 2,447 |
Ndtf [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 2,971 | 2,421
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 74 | 126
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 7,363 | 6,706
Debt securities, available-for-sale | 2,302 | 2,231
Equity Securities, FV-NI, Accumulated Unrealized Gain | 2,923 | 2,402
Equity Securities, FV-NI, Accumulated Unrealized Loss | 65 | 95
Cash and cash equivalents | 114 | 88
Equity securities, FV-NI | 5,061 | 4,475
Ndtf [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 17 | 4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 2 | 13
Debt securities, available-for-sale | 624 | 566
Ndtf [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 5 | 1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 4
Debt securities, available-for-sale | 317 | 353
Ndtf [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 25 | 14
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 5 | 12
Debt securities, available-for-sale | 1,102 | 1,076
Ndtf [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 1 |
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 2
Debt securities, available-for-sale | 145 | 148
Other Classification [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 51 | 37
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 2 | 5
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 422 | 369
Debt securities, available-for-sale | 310 | 270
Equity Securities, FV-NI, Accumulated Unrealized Gain | 47 | 36
Equity Securities, FV-NI, Accumulated Unrealized Loss |  | 1
Cash and cash equivalents | 51 | 22
Equity securities, FV-NI | 112 | 99
Other Classification [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 1 |
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax |  | 2
Debt securities, available-for-sale | 57 | 60
Other Classification [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 2 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 1
Debt securities, available-for-sale | 89 | 85
Other Classification [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 1 | 1
Debt securities, available-for-sale | 52 | 45
Other Classification [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 1
Debt securities, available-for-sale | 61 | 58
Duke Energy Carolinas [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale | 1,065 |
Duke Energy Carolinas [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 1,615 | 1,316
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 43 | 74
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 3,913 | 3,553
Debt securities, available-for-sale | 1,122 | 1,069
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,593 | 1,309
Equity Securities, FV-NI, Accumulated Unrealized Loss | 37 | 54
Cash and cash equivalents | 57 | 29
Equity securities, FV-NI | 2,791 | 2,484
Duke Energy Carolinas [Member] | Ndtf [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 9 | 2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 2 | 9
Debt securities, available-for-sale | 354 | 341
Duke Energy Carolinas [Member] | Ndtf [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 1 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 1
Debt securities, available-for-sale | 62 | 81
Duke Energy Carolinas [Member] | Ndtf [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 11 | 5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 3 | 8
Debt securities, available-for-sale | 509 | 475
Duke Energy Carolinas [Member] | Ndtf [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 1 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 2
Debt securities, available-for-sale | 140 | 143
Progress Energy [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 1,358 | 1,105
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 31 | 52
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 3,546 | 3,217
Debt securities, available-for-sale | 1,172 |
Progress Energy [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 1,356 | 1,105
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 31 | 52
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 3,450 | 3,153
Debt securities, available-for-sale | 1,180 | 1,162
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,330 | 1,093
Equity Securities, FV-NI, Accumulated Unrealized Loss | 28 | 41
Cash and cash equivalents | 57 | 59
Equity securities, FV-NI | 2,270 | 1,991
Progress Energy [Member] | Ndtf [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 8 | 2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax |  | 4
Debt securities, available-for-sale | 270 | 225
Progress Energy [Member] | Ndtf [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 4 | 1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 3
Debt securities, available-for-sale | 255 | 272
Progress Energy [Member] | Ndtf [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 14 | 9
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 2 | 4
Debt securities, available-for-sale | 593 | 601
Progress Energy [Member] | Ndtf [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale | 5 | 5
Progress Energy [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 2 | 0
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 96 | 64
Debt securities, available-for-sale | 96 | 64
Cash and cash equivalents | 47 | 17
Progress Energy [Member] | Other Classification [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 2 | 0
Debt securities, available-for-sale | 49 | 47
Duke Energy Progress [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 1,042 | 842
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 22 | 39
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 2,741 | 2,500
Debt securities, available-for-sale | 883 |
Duke Energy Progress [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 1,042 | 842
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 22 | 39
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 2,738 | 2,494
Debt securities, available-for-sale | 926 | 906
Equity Securities, FV-NI, Accumulated Unrealized Gain | 1,022 | 833
Equity Securities, FV-NI, Accumulated Unrealized Loss | 20 | 30
Cash and cash equivalents | 43 | 46
Equity securities, FV-NI | 1,812 | 1,588
Duke Energy Progress [Member] | Ndtf [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 6 | 2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 3
Debt securities, available-for-sale | 204 | 171
Duke Energy Progress [Member] | Ndtf [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 4 | 1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 3
Debt securities, available-for-sale | 254 | 271
Duke Energy Progress [Member] | Ndtf [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 10 | 6
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 3
Debt securities, available-for-sale | 422 | 415
Duke Energy Progress [Member] | Ndtf [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
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 | 3 | 3
Duke Energy Progress [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 3 | 6
Debt securities, available-for-sale | 3 | 6
Cash and cash equivalents | 3 | 6
Duke Energy Florida [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 316 | 263
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 9 | 13
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 762 | 707
Debt securities, available-for-sale | 289 |
Duke Energy Florida [Member] | Ndtf [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 314 | 263
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 9 | 13
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 712 | 659
Debt securities, available-for-sale | 254 | 256
Equity Securities, FV-NI, Accumulated Unrealized Gain | 308 | 260
Equity Securities, FV-NI, Accumulated Unrealized Loss | 8 | 11
Cash and cash equivalents | 14 | 13
Equity securities, FV-NI | 458 | 403
Duke Energy Florida [Member] | Ndtf [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 2 | 0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 0 | 1
Debt securities, available-for-sale | 66 | 54
Duke Energy Florida [Member] | Ndtf [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
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] | Ndtf [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 4 | 3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 1
Debt securities, available-for-sale | 171 | 186
Duke Energy Florida [Member] | Ndtf [Member] | Other debt obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
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] | Other Classification [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 2 |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 50 | 48
Debt securities, available-for-sale | 50 | 48
Cash and cash equivalents | 1 | 1
Duke Energy Florida [Member] | Other Classification [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax | 2 | 0
Debt securities, available-for-sale | 49 | 47
Duke Energy Indiana [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | 37 | 29
Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | 1 | 1
Debt Securities, Available-for-sale, and Equity Securities, FV-NI | 118 | 108
Debt securities, available-for-sale | 42 |
Equity Securities, FV-NI, Accumulated Unrealized Gain | 37 | 29
Equity securities, FV-NI | 76 | 67
Duke Energy Indiana [Member] | Corporate debt securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale | 7 | 8
Duke Energy Indiana [Member] | Municipal bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax | 1 | 1
Debt securities, available-for-sale | 34 | 33
Duke Energy Indiana [Member] | US treasury and government [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale | 1 | 0
Duke Energy Indiana [Member] | Other Classification [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Equity securities, FV-NI | $ 76 | $ 67

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