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Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | $ 2,899
Gross Unrealized Holding Losses |  | 42
Estimated Fair Value |  | 7,451
Debt Securities, Available-for-sale |  |
Estimated Fair Value | $ 2,391 |
Total Investments |  |
Unrealized Holding Gains | 2,458 |
Unrealized Holding Losses | 131 |
Estimated Fair Value | 7,075 |
NDTF [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 88 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2,837
Gross Unrealized Holding Losses |  | 40
Estimated Fair Value |  | 7,088
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 2,402 |
Gross Unrealized Holding Losses | 95 |
Estimated Fair Value | 4,475 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 2,231 |
Total Investments |  |
Unrealized Holding Gains | 2,421 |
Unrealized Holding Losses | 126 |
Estimated Fair Value | 6,706 |
NDTF [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 115
NDTF [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2,805
Gross Unrealized Holding Losses |  | 27
Estimated Fair Value |  | 4,914
NDTF [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 17
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 570
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 4 |
Gross Unrealized Holding Losses | 13 |
Estimated Fair Value | 566 |
NDTF [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 4
Gross Unrealized Holding Losses |  | 3
Estimated Fair Value |  | 344
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 |
Gross Unrealized Holding Losses | 4 |
Estimated Fair Value | 353 |
NDTF [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 11
Gross Unrealized Holding Losses |  | 7
Estimated Fair Value |  | 1,027
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 14 |
Gross Unrealized Holding Losses | 12 |
Estimated Fair Value | 1,076 |
NDTF [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 118
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Losses | 2 |
Estimated Fair Value | 148 |
Other Classification [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 22 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 62
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 363
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 36 |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 99 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 270 |
Total Investments |  |
Unrealized Holding Gains | 37 |
Unrealized Holding Losses | 5 |
Estimated Fair Value | 369 |
Other Classification [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 15
Other Classification [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 59
Estimated Fair Value |  | 123
Other Classification [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1
Estimated Fair Value |  | 57
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Losses | 2 |
Estimated Fair Value | 60 |
Other Classification [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 83
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 85 |
Other Classification [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 41
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 |
Estimated Fair Value | 45 |
Other Classification [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 44
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 58 |
Duke Energy Carolinas [Member] |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,040 |
Duke Energy Carolinas [Member] | NDTF [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 29 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1,543
Gross Unrealized Holding Losses |  | 20
Estimated Fair Value |  | 3,758
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,309 |
Gross Unrealized Holding Losses | 54 |
Estimated Fair Value | 2,484 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,069 |
Total Investments |  |
Unrealized Holding Gains | 1,316 |
Unrealized Holding Losses | 74 |
Estimated Fair Value | 3,553 |
Duke Energy Carolinas [Member] | NDTF [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 32
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1,531
Gross Unrealized Holding Losses |  | 12
Estimated Fair Value |  | 2,692
Duke Energy Carolinas [Member] | NDTF [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 9
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 359
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 2 |
Gross Unrealized Holding Losses | 9 |
Estimated Fair Value | 341 |
Duke Energy Carolinas [Member] | NDTF [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 60
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 81 |
Duke Energy Carolinas [Member] | NDTF [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 3
Gross Unrealized Holding Losses |  | 4
Estimated Fair Value |  | 503
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 5 |
Gross Unrealized Holding Losses | 8 |
Estimated Fair Value | 475 |
Duke Energy Carolinas [Member] | NDTF [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 112
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 2 |
Estimated Fair Value | 143 |
Progress Energy [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1,296
Gross Unrealized Holding Losses |  | 20
Estimated Fair Value |  | 3,389
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,150 |
Total Investments |  |
Unrealized Holding Gains | 1,105 |
Unrealized Holding Losses | 52 |
Estimated Fair Value | 3,217 |
Progress Energy [Member] | NDTF [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 59 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1,294
Gross Unrealized Holding Losses |  | 20
Estimated Fair Value |  | 3,330
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,093 |
Gross Unrealized Holding Losses | 41 |
Estimated Fair Value | 1,991 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,162 |
Total Investments |  |
Unrealized Holding Gains | 1,105 |
Unrealized Holding Losses | 52 |
Estimated Fair Value | 3,153 |
Progress Energy [Member] | NDTF [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 83
Progress Energy [Member] | NDTF [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 1,274
Gross Unrealized Holding Losses |  | 15
Estimated Fair Value |  | 2,222
Progress Energy [Member] | NDTF [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 8
Estimated Fair Value |  | 211
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 2 |
Gross Unrealized Holding Losses | 4 |
Estimated Fair Value | 225 |
Progress Energy [Member] | NDTF [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 4
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 284
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 |
Gross Unrealized Holding Losses | 3 |
Estimated Fair Value | 272 |
Progress Energy [Member] | NDTF [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 8
Gross Unrealized Holding Losses |  | 3
Estimated Fair Value |  | 524
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 9 |
Gross Unrealized Holding Losses | 4 |
Estimated Fair Value | 601 |
Progress Energy [Member] | NDTF [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 6
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 5 |
Progress Energy [Member] | Other Classification [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 17 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Estimated Fair Value |  | 59
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 64 |
Total Investments |  |
Unrealized Holding Gains | 0 |
Estimated Fair Value | 64 |
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 12
Progress Energy [Member] | Other Classification [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Estimated Fair Value |  | 47
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Estimated Fair Value | 47 |
Duke Energy Progress [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 995
Gross Unrealized Holding Losses |  | 16
Estimated Fair Value |  | 2,592
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 860 |
Total Investments |  |
Unrealized Holding Gains | 842 |
Unrealized Holding Losses | 39 |
Estimated Fair Value | 2,500 |
Duke Energy Progress [Member] | NDTF [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 46 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 995
Gross Unrealized Holding Losses |  | 16
Estimated Fair Value |  | 2,591
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 833 |
Gross Unrealized Holding Losses | 30 |
Estimated Fair Value | 1,588 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 906 |
Total Investments |  |
Unrealized Holding Gains | 842 |
Unrealized Holding Losses | 39 |
Estimated Fair Value | 2,494 |
Duke Energy Progress [Member] | NDTF [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 50
Duke Energy Progress [Member] | NDTF [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 980
Gross Unrealized Holding Losses |  | 12
Estimated Fair Value |  | 1,795
Duke Energy Progress [Member] | NDTF [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 6
Estimated Fair Value |  | 149
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 2 |
Gross Unrealized Holding Losses | 3 |
Estimated Fair Value | 171 |
Duke Energy Progress [Member] | NDTF [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 4
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 283
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 |
Gross Unrealized Holding Losses | 3 |
Estimated Fair Value | 271 |
Duke Energy Progress [Member] | NDTF [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 5
Gross Unrealized Holding Losses |  | 2
Estimated Fair Value |  | 310
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 6 |
Gross Unrealized Holding Losses | 3 |
Estimated Fair Value | 415 |
Duke Energy Progress [Member] | NDTF [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 4
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 3 |
Duke Energy Progress [Member] | Other Classification [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 6 |
Available-for-sale Securities |  |
Estimated Fair Value |  | 1
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 6 |
Total Investments |  |
Estimated Fair Value | 6 |
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 1
Duke Energy Florida [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 301
Gross Unrealized Holding Losses |  | 4
Estimated Fair Value |  | 787
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 290 |
Total Investments |  |
Unrealized Holding Gains | 263 |
Unrealized Holding Losses | 13 |
Estimated Fair Value | 707 |
Duke Energy Florida [Member] | NDTF [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 13 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 299
Gross Unrealized Holding Losses |  | 4
Estimated Fair Value |  | 739
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 260 |
Gross Unrealized Holding Losses | 11 |
Estimated Fair Value | 403 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 256 |
Total Investments |  |
Unrealized Holding Gains | 263 |
Unrealized Holding Losses | 13 |
Estimated Fair Value | 659 |
Duke Energy Florida [Member] | NDTF [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 33
Duke Energy Florida [Member] | NDTF [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 294
Gross Unrealized Holding Losses |  | 3
Estimated Fair Value |  | 427
Duke Energy Florida [Member] | NDTF [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Estimated Fair Value |  | 62
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 54 |
Duke Energy Florida [Member] | NDTF [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 1
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 1 |
Duke Energy Florida [Member] | NDTF [Member] | US Treasury and Government [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 3
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 214
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 186 |
Duke Energy Florida [Member] | NDTF [Member] | Other Debt Obligations [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 2
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 2 |
Duke Energy Florida [Member] | Other Classification [Member] |  |
Investment [Line Items] |  |
Cash And Cash Equivalent Investments | 1 |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Estimated Fair Value |  | 48
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 48 |
Total Investments |  |
Estimated Fair Value | 48 |
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 1
Duke Energy Florida [Member] | Other Classification [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 2
Estimated Fair Value |  | 47
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 |
Estimated Fair Value | 47 |
Duke Energy Indiana [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 49
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | 128
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 29 |
Estimated Fair Value | 67 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 41 |
Total Investments |  |
Unrealized Holding Gains | 29 |
Unrealized Holding Losses | 1 |
Estimated Fair Value | 108 |
Duke Energy Indiana [Member] | Equity Securities [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Gains |  | 49
Estimated Fair Value |  | 97
Duke Energy Indiana [Member] | Corporate Debt Securities [Member] |  |
Available-for-sale Securities |  |
Estimated Fair Value |  | 3
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 8 |
Duke Energy Indiana [Member] | Municipal Bonds [Member] |  |
Available-for-sale Securities |  |
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value |  | $ 28
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Losses | 1 |
Estimated Fair Value | 33 |
Duke Energy Indiana [Member] | Other Classification [Member] |  |
Equity Securities, FV-NI |  |
Estimated Fair Value | $ 67 |

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