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Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | $ 2,447 |
Derivative assets | 35 | $ 57
Total assets | 7,820 | 7,132
Derivative liabilities | (244) | (242)
Net assets (liabilities) | 7,576 | 6,890
Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 4
Total assets | 5,845 | 5,156
Derivative liabilities | (23) | (11)
Net assets (liabilities) | 5,822 | 5,145
Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 27 | 25
Total assets | 1,906 | 1,883
Derivative liabilities | (100) | (90)
Net assets (liabilities) | 1,806 | 1,793
Level 3 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 6 | 28
Total assets | 6 | 28
Derivative liabilities | (121) | (141)
Net assets (liabilities) | (115) | (113)
Fair Value Measured at Net Asset Value Per Share [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 63 | 65
Net assets (liabilities) | 63 | 65
Ndtf [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 5,061 | 4,475
Debt securities, available-for-sale | 2,302 | 2,231
Ndtf [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 4,998 | 4,410
Debt securities, available-for-sale | 630 | 576
Ndtf [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 1,672 | 1,655
Ndtf [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 63 | 65
Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 112 | 99
Debt securities, available-for-sale | 310 | 270
Other Classification [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 112 | 99
Debt securities, available-for-sale | 103 | 67
Other Classification [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 207 | 203
Duke Energy Carolinas [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 1,065 |
Derivative assets | 5 | 3
Total assets | 3,918 | 3,556
Derivative liabilities | (39) | (33)
Net assets (liabilities) | 3,879 | 3,523
Duke Energy Carolinas [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 2,940 | 2,568
Net assets (liabilities) | 2,940 | 2,568
Duke Energy Carolinas [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 5 | 3
Total assets | 915 | 923
Derivative liabilities | (39) | (33)
Net assets (liabilities) | 876 | 890
Duke Energy Carolinas [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 63 | 65
Net assets (liabilities) | 63 | 65
Duke Energy Carolinas [Member] | Ndtf [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 2,791 | 2,484
Debt securities, available-for-sale | 1,122 | 1,069
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 2,728 | 2,419
Debt securities, available-for-sale | 212 | 149
Duke Energy Carolinas [Member] | Ndtf [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 910 | 920
Duke Energy Carolinas [Member] | Ndtf [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 63 | 65
Progress Energy [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 1,172 |
Derivative assets | 8 | 4
Total assets | 3,554 | 3,221
Derivative liabilities | (44) | (44)
Net assets (liabilities) | 3,510 | 3,177
Progress Energy [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 |
Total assets | 2,735 | 2,435
Derivative liabilities | 0 |
Net assets (liabilities) | 2,735 | 2,435
Progress Energy [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 8 | 4
Total assets | 819 | 786
Derivative liabilities | (44) | (44)
Net assets (liabilities) | 775 | 742
Progress Energy [Member] | Ndtf [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 2,270 | 1,991
Debt securities, available-for-sale | 1,180 | 1,162
Progress Energy [Member] | Ndtf [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 2,270 | 1,991
Debt securities, available-for-sale | 418 | 427
Progress Energy [Member] | Ndtf [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 762 | 735
Progress Energy [Member] | Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 96 | 64
Progress Energy [Member] | Other Classification [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 47 | 17
Progress Energy [Member] | Other Classification [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 49 | 47
Duke Energy Progress [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 883 |
Derivative assets | 8 | 4
Total assets | 2,749 | 2,504
Derivative liabilities | (12) | (27)
Net assets (liabilities) | 2,737 | 2,477
Duke Energy Progress [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 |
Total assets | 2,113 | 1,888
Derivative liabilities | 0 |
Net assets (liabilities) | 2,113 | 1,888
Duke Energy Progress [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 8 | 4
Total assets | 636 | 616
Derivative liabilities | (12) | (27)
Net assets (liabilities) | 624 | 589
Duke Energy Progress [Member] | Ndtf [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 1,812 | 1,588
Debt securities, available-for-sale | 926 | 906
Duke Energy Progress [Member] | Ndtf [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 1,812 | 1,588
Debt securities, available-for-sale | 298 | 294
Duke Energy Progress [Member] | Ndtf [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 628 | 612
Duke Energy Progress [Member] | Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 3 | 6
Duke Energy Progress [Member] | Other Classification [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 3 | 6
Duke Energy Florida [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 289 |
Total assets | 762 | 707
Derivative liabilities | (18) | (9)
Net assets (liabilities) | 744 | 698
Duke Energy Florida [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 579 | 537
Net assets (liabilities) | 579 | 537
Duke Energy Florida [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 183 | 170
Derivative liabilities | (18) | (9)
Net assets (liabilities) | 165 | 161
Duke Energy Florida [Member] | Ndtf [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 458 | 403
Debt securities, available-for-sale | 254 | 256
Duke Energy Florida [Member] | Ndtf [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 458 | 403
Debt securities, available-for-sale | 120 | 133
Duke Energy Florida [Member] | Ndtf [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 134 | 123
Duke Energy Florida [Member] | Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 50 | 48
Duke Energy Florida [Member] | Other Classification [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 1 | 1
Duke Energy Florida [Member] | Other Classification [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 49 | 47
Duke Energy Indiana [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 76 | 67
Debt securities, available-for-sale | 42 |
Derivative assets | 5 | 23
Total assets | 123 | 131
Duke Energy Indiana [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 0 | 1
Total assets | 76 | 68
Duke Energy Indiana [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total assets | 42 | 41
Duke Energy Indiana [Member] | Level 3 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 5 | 22
Total assets | 5 | 22
Duke Energy Indiana [Member] | Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 76 | 67
Duke Energy Indiana [Member] | Other Classification [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities, FV-NI | 76 | 67
Piedmont Natural Gas [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 3
Derivative liabilities | (121) | (141)
Net assets (liabilities) | (119) | (138)
Piedmont Natural Gas [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative assets | 2 | 3
Net assets (liabilities) | 2 | 3
Piedmont Natural Gas [Member] | Level 3 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Derivative liabilities | (121) | (141)
Net assets (liabilities) | (121) | (141)
Debt Securities [Member] | Duke Energy Indiana [Member] | Other Classification [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | 42 | 41
Debt Securities [Member] | Duke Energy Indiana [Member] | Other Classification [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt securities, available-for-sale | $ 42 | $ 41

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