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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, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale |  |
Estimated Fair Value | $ 2,626 |
Total Investments |  |
Unrealized Holding Gains | 3,675 | $ 2,458
Unrealized Holding Losses | 57 | 131
Estimated Fair Value | 8,562 | 7,075
NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 3,523 | 2,402
Gross Unrealized Holding Losses | 55 | 95
Estimated Fair Value | 5,661 | 4,475
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 2,469 | 2,231
Total Investments |  |
Unrealized Holding Gains | 3,609 | 2,421
Unrealized Holding Losses | 57 | 126
Estimated Fair Value | 8,130 | 6,706
NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 101 | 88
NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 37 | 4
Gross Unrealized Holding Losses | 1 | 13
Estimated Fair Value | 603 | 566
NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 13 | 1
Gross Unrealized Holding Losses | 0 | 4
Estimated Fair Value | 368 | 353
NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 33 | 14
Gross Unrealized Holding Losses | 1 | 12
Estimated Fair Value | 1,256 | 1,076
NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 2
Estimated Fair Value | 141 | 148
Other Investments |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 57 | 36
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 122 | 99
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 310 | 270
Total Investments |  |
Unrealized Holding Gains | 66 | 37
Unrealized Holding Losses | 0 | 5
Estimated Fair Value | 432 | 369
Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 52 | 22
Other Investments | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 2
Estimated Fair Value | 67 | 60
Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 4 | 0
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 94 | 85
Other Investments | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 2 | 1
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 41 | 45
Other Investments | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 56 | 58
Duke Energy Carolinas |  |
Equity Securities, FV-NI |  |
Estimated Fair Value |  | 2,484
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,172 |
Duke Energy Carolinas | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,914 | 1,309
Gross Unrealized Holding Losses | 8 | 54
Estimated Fair Value | 3,154 | 2,484
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,193 | 1,069
Total Investments |  |
Unrealized Holding Gains | 1,957 | 1,316
Unrealized Holding Losses | 10 | 74
Estimated Fair Value | 4,347 | 3,553
Duke Energy Carolinas | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 21 | 29
Duke Energy Carolinas | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 21 | 2
Gross Unrealized Holding Losses | 1 | 9
Estimated Fair Value | 361 | 341
Duke Energy Carolinas | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 96 | 81
Duke Energy Carolinas | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 5
Gross Unrealized Holding Losses | 1 | 8
Estimated Fair Value | 578 | 475
Duke Energy Carolinas | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 2
Estimated Fair Value | 137 | 143
Progress Energy |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,247 |
Total Investments |  |
Unrealized Holding Gains | 1,655 | 1,105
Unrealized Holding Losses | 47 | 52
Estimated Fair Value | 3,883 | 3,217
Progress Energy | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,609 | 1,093
Gross Unrealized Holding Losses | 47 | 41
Estimated Fair Value | 2,507 | 1,991
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,276 | 1,162
Total Investments |  |
Unrealized Holding Gains | 1,652 | 1,105
Unrealized Holding Losses | 47 | 52
Estimated Fair Value | 3,783 | 3,153
Progress Energy | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 80 | 59
Progress Energy | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 2
Gross Unrealized Holding Losses | 0 | 4
Estimated Fair Value | 242 | 225
Progress Energy | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 10 | 1
Gross Unrealized Holding Losses | 0 | 3
Estimated Fair Value | 272 | 272
Progress Energy | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 17 | 9
Gross Unrealized Holding Losses | 0 | 4
Estimated Fair Value | 678 | 601
Progress Energy | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 4 | 5
Progress Energy | Other Investments |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 100 | 64
Total Investments |  |
Unrealized Holding Gains | 3 | 0
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 100 | 64
Progress Energy | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 49 | 17
Progress Energy | Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 51 | 47
Duke Energy Progress |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 921 |
Total Investments |  |
Unrealized Holding Gains | 1,300 | 842
Unrealized Holding Losses | 21 | 39
Estimated Fair Value | 3,053 | 2,500
Duke Energy Progress | NDTF |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 53 |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,258 | 833
Gross Unrealized Holding Losses | 21 | 30
Estimated Fair Value | 2,077 | 1,588
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 974 | 906
Total Investments |  |
Unrealized Holding Gains | 1,300 | 842
Unrealized Holding Losses | 21 | 39
Estimated Fair Value | 3,051 | 2,494
Duke Energy Progress | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments |  | 46
Duke Energy Progress | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 2
Gross Unrealized Holding Losses | 0 | 3
Estimated Fair Value | 242 | 171
Duke Energy Progress | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 10 | 1
Gross Unrealized Holding Losses | 0 | 3
Estimated Fair Value | 272 | 271
Duke Energy Progress | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 6
Gross Unrealized Holding Losses | 0 | 3
Estimated Fair Value | 403 | 415
Duke Energy Progress | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 4 | 3
Duke Energy Progress | Other Investments |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 2 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 2 | 6
Total Investments |  |
Unrealized Holding Gains | 0 | 0
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 2 | 6
Duke Energy Progress | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments |  | 6
Duke Energy Florida |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 326 |
Total Investments |  |
Unrealized Holding Gains | 355 | 263
Unrealized Holding Losses | 26 | 13
Estimated Fair Value | 787 | 707
Duke Energy Florida | NDTF |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 27 |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 351 | 260
Gross Unrealized Holding Losses | 26 | 11
Estimated Fair Value | 430 | 403
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 302 | 256
Total Investments |  |
Unrealized Holding Gains | 352 | 263
Unrealized Holding Losses | 26 | 13
Estimated Fair Value | 732 | 659
Duke Energy Florida | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments |  | 13
Duke Energy Florida | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 0 | 54
Duke Energy Florida | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 0 | 1
Duke Energy Florida | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 | 3
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 275 | 186
Duke Energy Florida | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 0 | 2
Duke Energy Florida | Other Investments |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments | 4 |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 55 | 48
Total Investments |  |
Unrealized Holding Gains | 3 | 0
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 55 | 48
Duke Energy Florida | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash And Cash Equivalent Investments |  | 1
Duke Energy Florida | Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 51 | 47
Duke Energy Indiana |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 43 | 29
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 81 | 67
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 44 |
Total Investments |  |
Unrealized Holding Gains | 44 | 29
Unrealized Holding Losses |  | 1
Estimated Fair Value | 125 | 108
Duke Energy Indiana | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 6 | 8
Duke Energy Indiana | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 | 0
Gross Unrealized Holding Losses | 0 | 1
Estimated Fair Value | 36 | 33
Duke Energy Indiana | Other Investments |  |
Equity Securities, FV-NI |  |
Estimated Fair Value | 81 | 67
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 44 | 41
Duke Energy Indiana | Other Investments | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Estimated Fair Value | $ 2 | $ 0

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