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Employee Benefit Plans (Employee Savings Plans) (Details) - Employee Savings Plan [Member] - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | $ 49 | $ 43 | $ 167 | $ 147
Duke Energy Carolinas [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | 15 | 14 | 53 | 49
Progress Energy [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | 13 | 12 | 45 | 42
Duke Energy Progress [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | 9 | 9 | 31 | 30
Duke Energy Florida [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | 4 | 4 | 14 | 13
Duke Energy Ohio [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | 1 | 2 | 3
Duke Energy Indiana [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | 3 | 2 | 8 | 7
Piedmont Natural Gas [Member] |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Employer contributions | $ 4 | $ 2 | $ 10 | $ 5

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + 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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- Details
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- Details
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- Details
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