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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, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale |  |
Estimated Fair Value | $ 3,002 |
Total Investments |  |
Unrealized Holding Gains | 4,387 | $ 3,675
Unrealized Holding Losses | 55 | 57
Estimated Fair Value | 9,687 | 8,562
NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 4,138 | 3,523
Gross Unrealized Holding Losses | 54 | 55
Estimated Fair Value | 6,235 | 5,661
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 2,717 | 2,368
Total Investments |  |
Unrealized Holding Gains | 4,295 | 3,609
Unrealized Holding Losses | 55 | 57
Estimated Fair Value | 9,129 | 8,130
NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 177 | 101
NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 76 | 37
Gross Unrealized Holding Losses | 1 | 1
Estimated Fair Value | 806 | 603
NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 22 | 13
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 370 | 368
NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 51 | 33
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value | 1,361 | 1,256
NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 8 | 3
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 180 | 141
Other Investments |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 79 | 57
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 146 | 122
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 285 | 258
Total Investments |  |
Unrealized Holding Gains | 92 | 66
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 558 | 432
Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 127 | 52
Other Investments | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 8 | 3
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 110 | 67
Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 5 | 4
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 86 | 94
Other Investments | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 2
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 42 | 41
Other Investments | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 47 | 56
Duke Energy Carolinas |  |
Equity Securities, FV-NI |  |
Estimated Fair Value |  | 3,154
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,250 |
Duke Energy Carolinas | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 2,442 | 1,914
Gross Unrealized Holding Losses | 23 | 8
Estimated Fair Value | 3,685 | 3,154
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,250 | 1,172
Total Investments |  |
Unrealized Holding Gains | 2,529 | 1,957
Unrealized Holding Losses | 24 | 10
Estimated Fair Value | 4,965 | 4,347
Duke Energy Carolinas | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 30 | 21
Duke Energy Carolinas | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 49 | 21
Gross Unrealized Holding Losses | 1 | 1
Estimated Fair Value | 510 | 361
Duke Energy Carolinas | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 6 | 3
Estimated Fair Value | 91 | 96
Duke Energy Carolinas | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 25 | 16
Gross Unrealized Holding Losses |  | 1
Estimated Fair Value | 475 | 578
Duke Energy Carolinas | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 7 | 3
Estimated Fair Value | 174 | 137
Progress Energy |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,493 |
Total Investments |  |
Unrealized Holding Gains | 1,769 | 1,655
Unrealized Holding Losses | 31 | 47
Estimated Fair Value | 4,296 | 3,883
Progress Energy | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,696 | 1,609
Gross Unrealized Holding Losses | 31 | 47
Estimated Fair Value | 2,550 | 2,507
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 1,467 | 1,196
Total Investments |  |
Unrealized Holding Gains | 1,766 | 1,652
Unrealized Holding Losses | 31 | 47
Estimated Fair Value | 4,164 | 3,783
Progress Energy | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 147 | 80
Progress Energy | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 27 | 16
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 296 | 242
Progress Energy | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 10
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 279 | 272
Progress Energy | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 26 | 17
Gross Unrealized Holding Losses | 0 |
Estimated Fair Value | 886 | 678
Progress Energy | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 6 | 4
Progress Energy | Other Investments |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 26 | 51
Total Investments |  |
Unrealized Holding Gains | 3 | 3
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 132 | 100
Progress Energy | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 106 | 49
Progress Energy | Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 3
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 26 | 51
Duke Energy Progress |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 993 |
Total Investments |  |
Unrealized Holding Gains | 1,687 | 1,300
Unrealized Holding Losses | 31 | 21
Estimated Fair Value | 3,529 | 3,053
Duke Energy Progress | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 1,617 | 1,258
Gross Unrealized Holding Losses | 31 | 21
Estimated Fair Value | 2,459 | 2,077
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 993 | 921
Total Investments |  |
Unrealized Holding Gains | 1,687 | 1,300
Unrealized Holding Losses | 31 | 21
Estimated Fair Value | 3,528 | 3,051
Duke Energy Progress | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 76 | 53
Duke Energy Progress | NDTF | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 27 | 16
Estimated Fair Value | 296 | 242
Duke Energy Progress | NDTF | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 16 | 10
Estimated Fair Value | 279 | 272
Duke Energy Progress | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 26 | 16
Estimated Fair Value | 412 | 403
Duke Energy Progress | NDTF | Other debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 6 | 4
Duke Energy Progress | Other Investments |  |
Total Investments |  |
Unrealized Holding Gains | 0 | 0
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 1 | 2
Duke Energy Progress | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 1 | 2
Duke Energy Florida |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 500 |
Total Investments |  |
Unrealized Holding Gains | 82 | 355
Unrealized Holding Losses | 0 | 26
Estimated Fair Value | 663 | 787
Duke Energy Florida | NDTF |  |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 79 | 351
Gross Unrealized Holding Losses |  | 26
Estimated Fair Value | 91 | 430
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 474 | 275
Total Investments |  |
Unrealized Holding Gains | 79 | 352
Unrealized Holding Losses | 0 | 26
Estimated Fair Value | 636 | 732
Duke Energy Florida | NDTF | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 71 | 27
Duke Energy Florida | NDTF | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains |  | 1
Estimated Fair Value | 474 | 275
Duke Energy Florida | Other Investments |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 26 | 51
Total Investments |  |
Unrealized Holding Gains | 3 | 3
Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 27 | 55
Duke Energy Florida | Other Investments | Cash and cash equivalents |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 1 | 4
Duke Energy Florida | Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 3 | 3
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 26 | 51
Duke Energy Indiana |  |
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 45 |
Total Investments |  |
Unrealized Holding Gains | 59 | 44
Unrealized Holding Losses |  | 0
Estimated Fair Value | 143 | 125
Duke Energy Indiana | Other Investments |  |
Available-for-sale Securities |  |
Cash and cash equivalents | 1 |
Equity Securities, FV-NI |  |
Gross Unrealized Holding Gains | 58 | 43
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 97 | 81
Debt Securities, Available-for-sale |  |
Estimated Fair Value | 45 | 44
Duke Energy Indiana | Other Investments | Corporate debt securities |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 3 | 6
Duke Energy Indiana | Other Investments | Municipal bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 1 | 1
Gross Unrealized Holding Losses | 0 | 0
Estimated Fair Value | 38 | 36
Duke Energy Indiana | Other Investments | U.S. government bonds |  |
Debt Securities, Available-for-sale |  |
Gross Unrealized Holding Gains | 0 | 0
Estimated Fair Value | $ 4 | $ 2

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