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Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Assets) (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 USD ($) $ / MWh | Dec. 31, 2017 USD ($) $ / MWh | Dec. 31, 2016 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Net Derivative Asset (Liability) | $ (113) | $ (114) | $ (166)
Duke Energy Ohio [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Net Derivative Asset (Liability) | 6 | 1 | 5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Net Derivative Asset (Liability) | $ 6 | $ 1 |
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value Input Price Per Unit | $ / MWh | 1.19 | 0.07 |
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value Input Price Per Unit | $ / MWh | 4.59 | 1.41 |
Duke Energy Indiana [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Net Derivative Asset (Liability) | $ 22 | $ 27 | $ 16
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Net Derivative Asset (Liability) | $ 22 | $ 27 |
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value Input Price Per Unit | $ / MWh | (2.07) | (0.77) |
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value Input Price Per Unit | $ / MWh | 8.27 | 7.44 |

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