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Fair Value Measurements (Reconciliation of Assets and Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs) (Details) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement, transfers between activity levels | $ 0 | $ 0 | $ 0 | $ 0
Derivatives (net) |  |  |  |
Balance at beginning of period | (115,000,000) | (124,000,000) | (113,000,000) | (114,000,000)
Purchases, sales, issuances and settlements: |  |  |  |
Purchases | 38,000,000 | 56,000,000 | 38,000,000 | 56,000,000
Settlements | (11,000,000) | 15,000,000 | (23,000,000) | (29,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet | 9,000,000 | (14,000,000) | 19,000,000 | (10,000,000)
Balance at end of period | (79,000,000) | (97,000,000) | (79,000,000) | (97,000,000)
Duke Energy Indiana [Member] |  |  |  |
Derivatives (net) |  |  |  |
Balance at beginning of period | 5,000,000 |  | 22,000,000 | 27,000,000
Purchases, sales, issuances and settlements: |  |  |  |
Purchases | 29,000,000 | 49,000,000 | 29,000,000 | 49,000,000
Settlements | (9,000,000) | (14,000,000) | (19,000,000) | (28,000,000)
Total gains (losses) included on the Condensed Consolidated Balance Sheet | 3,000,000 | 2,000,000 | (4,000,000) | (4,000,000)
Balance at end of period | 28,000,000 | 44,000,000 | 28,000,000 | 44,000,000
Piedmont Natural Gas [Member] |  |  |  |
Derivatives (net) |  |  |  |
Balance at beginning of period | (121,000,000) | (132,000,000) | (141,000,000) | (142,000,000)
Purchases, sales, issuances and settlements: |  |  |  |
Total gains (losses) and settlements | 7,000,000 | (18,000,000) | 27,000,000 | (8,000,000)
Balance at end of period | $ (114,000,000) | $ (150,000,000) | $ (114,000,000) | $ (150,000,000)

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- Definition Total amount, including deferred gains or losses, recorded as regulatory assets and liabilities [net] measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period. + References No definition available. + Details
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