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Investments in Debt and Equity Securities (Available-For-Sale Investments) (Details) - USD ($)
$ in Millions
Sep. 30, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains $ 2,636 $ 2,156
Gross Unrealized Holding Losses 38 88
Estimated Fair Value 7,152 6,554
Ndtf [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 2,580 2,115
Gross Unrealized Holding Losses 37 83
Estimated Fair Value 6,794 6,184
Ndtf [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 129 111
Ndtf [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 2,549 2,092
Gross Unrealized Holding Losses 28 54
Estimated Fair Value 4,627 4,106
Ndtf [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 16 10
Gross Unrealized Holding Losses 2 8
Estimated Fair Value 600 528
Ndtf [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 5 3
Gross Unrealized Holding Losses 2 10
Estimated Fair Value 334 331
Ndtf [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 10 10
Gross Unrealized Holding Losses 4 8
Estimated Fair Value 984 984
Ndtf [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses 1 3
Estimated Fair Value 120 124
Other Classification [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 56 41
Gross Unrealized Holding Losses 1 5
Estimated Fair Value 358 370
Other Classification [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 15 25
Other Classification [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 52 38
Estimated Fair Value 115 104
Other Classification [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1 1
Gross Unrealized Holding Losses   1
Estimated Fair Value 64 66
Other Classification [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Gross Unrealized Holding Losses 1 1
Estimated Fair Value 83 82
Other Classification [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses   1
Estimated Fair Value 44 51
Other Classification [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses   2
Estimated Fair Value 37 42
Duke Energy Carolinas [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,408 1,165
Gross Unrealized Holding Losses 20 45
Estimated Fair Value 3,613 3,261
Duke Energy Carolinas [Member] | Ndtf [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,408 1,165
Gross Unrealized Holding Losses 20 44
Estimated Fair Value 3,613 3,258
Duke Energy Carolinas [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 34 18
Duke Energy Carolinas [Member] | Ndtf [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,395 1,157
Gross Unrealized Holding Losses 14 28
Estimated Fair Value 2,553 2,245
Duke Energy Carolinas [Member] | Ndtf [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 9 5
Gross Unrealized Holding Losses 2 6
Estimated Fair Value 395 354
Duke Energy Carolinas [Member] | Ndtf [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1 1
Gross Unrealized Holding Losses   2
Estimated Fair Value 52 67
Duke Energy Carolinas [Member] | Ndtf [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Gross Unrealized Holding Losses 3 5
Estimated Fair Value 466 458
Duke Energy Carolinas [Member] | Ndtf [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses 1 3
Estimated Fair Value 113 116
Duke Energy Carolinas [Member] | Other Classification [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses   1
Estimated Fair Value   3
Progress Energy [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,175 952
Gross Unrealized Holding Losses 17 39
Estimated Fair Value 3,239 2,991
Progress Energy [Member] | Ndtf [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,172 950
Gross Unrealized Holding Losses 17 39
Estimated Fair Value 3,181 2,926
Progress Energy [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 95 93
Progress Energy [Member] | Ndtf [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 1,154 935
Gross Unrealized Holding Losses 14 26
Estimated Fair Value 2,074 1,861
Progress Energy [Member] | Ndtf [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 7 5
Gross Unrealized Holding Losses   2
Estimated Fair Value 205 174
Progress Energy [Member] | Ndtf [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 4 2
Gross Unrealized Holding Losses 2 8
Estimated Fair Value 282 264
Progress Energy [Member] | Ndtf [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 7 8
Gross Unrealized Holding Losses 1 3
Estimated Fair Value 518 526
Progress Energy [Member] | Ndtf [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 7 8
Progress Energy [Member] | Other Classification [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Estimated Fair Value 58 65
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 11 21
Progress Energy [Member] | Other Classification [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Estimated Fair Value 47 44
Duke Energy Progress [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 896 715
Gross Unrealized Holding Losses 14 32
Estimated Fair Value 2,462 2,214
Duke Energy Progress [Member] | Ndtf [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 896 715
Gross Unrealized Holding Losses 14 32
Estimated Fair Value 2,461 2,213
Duke Energy Progress [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 46 45
Duke Energy Progress [Member] | Ndtf [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 882 704
Gross Unrealized Holding Losses 11 21
Estimated Fair Value 1,683 1,505
Duke Energy Progress [Member] | Ndtf [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 5 4
Gross Unrealized Holding Losses   1
Estimated Fair Value 144 120
Duke Energy Progress [Member] | Ndtf [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 4 2
Gross Unrealized Holding Losses 2 8
Estimated Fair Value 281 263
Duke Energy Progress [Member] | Ndtf [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 5 5
Gross Unrealized Holding Losses 1 2
Estimated Fair Value 303 275
Duke Energy Progress [Member] | Ndtf [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 4 5
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 1 1
Duke Energy Florida [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 279 237
Gross Unrealized Holding Losses 3 7
Estimated Fair Value 767 761
Duke Energy Florida [Member] | Ndtf [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 276 235
Gross Unrealized Holding Losses 3 7
Estimated Fair Value 720 713
Duke Energy Florida [Member] | Ndtf [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 49 48
Duke Energy Florida [Member] | Ndtf [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 272 231
Gross Unrealized Holding Losses 3 5
Estimated Fair Value 391 356
Duke Energy Florida [Member] | Ndtf [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 2 1
Gross Unrealized Holding Losses   1
Estimated Fair Value 61 54
Duke Energy Florida [Member] | Ndtf [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 1 1
Duke Energy Florida [Member] | Ndtf [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 2 3
Gross Unrealized Holding Losses   1
Estimated Fair Value 215 251
Duke Energy Florida [Member] | Ndtf [Member] | Other Debt Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 3 3
Duke Energy Florida [Member] | Other Classification [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Estimated Fair Value 47 48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value   4
Duke Energy Florida [Member] | Other Classification [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 3 2
Estimated Fair Value 47 44
Duke Energy Indiana [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 44 33
Gross Unrealized Holding Losses 1 1
Estimated Fair Value 122 110
Duke Energy Indiana [Member] | Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Gains 44 33
Estimated Fair Value 91 79
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value 3 2
Duke Energy Indiana [Member] | Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Holding Losses 1 1
Estimated Fair Value $ 28 28
Duke Energy Indiana [Member] | US Treasury and Government [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated Fair Value   $ 1