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Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) | 2 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 31, 2016
Employee Savings Plans [Abstract] |  |  |  |  |
Matching contribution percentage |  | 100.00% |  |  |
Eligible pay percentage |  | 6.00% |  |  |
Additional contribution percentage for employees not participating in defined pension plans |  | 4.00% |  |  |
Employer contributions |  | $ 213,000,000 | $ 179,000,000 | $ 169,000,000 |
Duke Energy Carolinas [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | 68,000,000 | 61,000,000 | 57,000,000 |
Progress Energy [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | 58,000,000 | 53,000,000 | 50,000,000 |
Duke Energy Progress [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | 40,000,000 | 37,000,000 | 35,000,000 |
Duke Energy Florida [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | 19,000,000 | 16,000,000 | 15,000,000 |
Duke Energy Ohio [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | 4,000,000 | 3,000,000 | 3,000,000 |
Duke Energy Indiana [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions |  | $ 10,000,000 | 9,000,000 | 8,000,000 |
Piedmont Natural Gas [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Additional contribution percentage for employees not participating in defined pension plans |  | 4.00% |  |  |
Employer contributions |  |  | 7,000,000 |  |
Piedmont Natural Gas [Member] | Pension Plan [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Eligible pay percentage |  | 4.00% |  |  |
Employer contributions | $ 0 |  | $ 2,000,000 |  | $ 2,000,000
Piedmont Natural Gas [Member] | 401K [Member] |  |  |  |  |
Employee Savings Plans [Abstract] |  |  |  |  |
Employer contributions | $ 1,000,000 | $ 12,000,000 |  |  | $ 7,000,000

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- Definition Percentage of eligible pay per period contributed to an employee's 401(k) account in lieu of participation in Duke Energy's defined pension plans. + References No definition available. + Details
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- References No definition available. + Details
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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 Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
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