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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
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Mar. 31, 2019 | Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair value measurement, transfers between activity levels | $ 0 | $ 0
Derivatives (net) |  |
Balance at beginning of period | (113,000,000) | (114,000,000)
Purchases, sales, issuances and settlements: |  |
Settlements | (12,000,000) | (14,000,000)
Total gains included on the Condensed Consolidated Balance Sheet | 10,000,000 | 4,000,000
Balance at end of period | (115,000,000) | (124,000,000)
Duke Energy Indiana [Member] |  |
Derivatives (net) |  |
Balance at beginning of period | 22,000,000 | 27,000,000
Purchases, sales, issuances and settlements: |  |
Settlements | (10,000,000) | (14,000,000)
Total gains included on the Condensed Consolidated Balance Sheet | (7,000,000) | (6,000,000)
Balance at end of period | 5,000,000 | 7,000,000
Piedmont Natural Gas [Member] |  |
Derivatives (net) |  |
Balance at beginning of period | (141,000,000) | (142,000,000)
Purchases, sales, issuances and settlements: |  |
Total gains and settlements | 20,000,000 | 10,000,000
Balance at end of period | $ (121,000,000) | $ (132,000,000)

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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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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of increase (decrease) of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19279-110258 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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- Definition Amount of settlements of financial instrument classified as a derivative asset (liability) after deduction of derivative liability, measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19279-110258 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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