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Debt and Credit Facilities (Summary of Debt Issuances) (Details) - USD ($) | 1 Months Ended | 9 Months Ended
--- | --- | ---
Apr. 30, 2018 | Sep. 30, 2018 | Sep. 30, 2017
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 4,050,000,000 |
Repayments of long-term debt |  | 2,278,000,000 | $ 2,035,000,000
Parent Company [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 1,250,000,000 |
Duke Energy Carolinas [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 1,000,000,000 |
Repayments of long-term debt |  | 704,000,000 | 115,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing April 2018, 5.100% Coupon |  |  |
Debt Instrument [Line Items] |  |  |
Repayments of long-term debt | $ 300,000,000 |  |
Duke Energy Progress [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 800,000,000 |
Repayments of long-term debt |  | 2,000,000 | 270,000,000
Duke Energy Florida [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 1,000,000,000 |
Repayments of long-term debt |  | 717,000,000 | $ 341,000,000
Unsecured Debt [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 250,000,000 |
Interest rate |  | 3.95% |
Unsecured Debt [Member] | May 2018 Debt Issuance 2.819% Coupon Due 2021 [Member] [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
Interest rate |  | 2.819% |
Unsecured Debt [Member] | September 2018 Debt Issuance 5.625% Coupon Due 2078 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
Interest rate |  | 5.625% |
Unsecured Debt [Member] | Parent Company [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 250,000,000 |
Unsecured Debt [Member] | Parent Company [Member] | May 2018 Debt Issuance 2.819% Coupon Due 2021 [Member] [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 500,000,000 |
Unsecured Debt [Member] | Parent Company [Member] | September 2018 Debt Issuance 5.625% Coupon Due 2078 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 500,000,000 |
First Mortgage [Member] | March 2018 Debt Issuance 3.050% Coupon Due 2023 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
Interest rate |  | 3.05% |
First Mortgage [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
Interest rate |  | 3.95% |
First Mortgage [Member] | June 2018 Debt issuance 3.80% coupon Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 600,000,000 |
Interest rate |  | 3.80% |
First Mortgage [Member] | June 2018 Debt Issuance 4.20 Coupon Due 2048 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 400,000,000 |
Interest rate |  | 4.20% |
First Mortgage [Member] | August 2018 Debt Issuance 3.375% Coupon Due 2023 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 300,000,000 |
Interest rate |  | 3.375% |
First Mortgage [Member] | August 2018 Debt Issuance 3.700% Coupon Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
Interest rate |  | 3.70% |
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.050% Coupon Due 2023 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 500,000,000 |
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2018 Debt Issuance 3.950% Coupon Due 2048 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 500,000,000 |
First Mortgage [Member] | Duke Energy Progress [Member] | August 2018 Debt Issuance 3.375% Coupon Due 2023 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 300,000,000 |
First Mortgage [Member] | Duke Energy Progress [Member] | August 2018 Debt Issuance 3.700% Coupon Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 500,000,000 |
First Mortgage [Member] | Duke Energy Florida [Member] | June 2018 Debt issuance 3.80% coupon Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | 600,000,000 |
First Mortgage [Member] | Duke Energy Florida [Member] | June 2018 Debt Issuance 4.20 Coupon Due 2048 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt issuances |  | $ 400,000,000 |

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