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Debt and Credit Facilities (Narrative) (Details) | 1 Months Ended | 2 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jan. 31, 2019 USD ($) | Feb. 28, 2019 USD ($) | Dec. 31, 2018 USD ($) | Aug. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances |  |  | $ 5,050,000,000 |  | $ 6,070,000,000
Other Debt Matters [Abstract] |  |  |  |  |
Demand notes, maximum amount available for sale |  |  | 3,000,000,000 |  |
Demand notes, maximum amount outstanding |  |  | 1,500,000,000 |  |
Principal amount of demand notes |  |  | 1,010,000,000 |  | 986,000,000
Other Loans [Abstract] |  |  |  |  |
Other loans outstanding against cash surrender value of life insurance policies |  |  | $ 741,000,000 |  | 701,000,000
Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 8,000,000,000 |  |
Line of credit facility, expiration date |  |  | Mar. 16, 2023 |  |
June 2017 Three Year Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 1,000,000,000.0 |  |
Debt Instrument, Term |  |  | 3 years |  |
Long-term Line of Credit |  |  | $ 500,000,000 |  |
Term Loan Proceeds |  |  | 500,000,000 |  |
Duke Energy Carolinas [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances |  |  | $ 2,000,000,000 |  | 550,000,000
Duke Energy Carolinas [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 1,750,000,000 |  |
Progress Energy [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Progress [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances |  |  | $ 800,000,000 |  | 800,000,000
Other Loans [Abstract] |  |  |  |  |
Other loans outstanding against cash surrender value of life insurance policies |  |  | $ 37,000,000 |  | 38,000,000
Duke Energy Progress [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Progress [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 1,400,000,000 |  |
Duke Energy Progress [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 700,000,000 |  |
Debt Instrument, Term |  |  | 2 years |  |
Long-term Line of Credit |  |  | $ 50,000,000 |  |
Term Loan Proceeds |  |  | 50,000,000 |  |
Duke Energy Progress [Member] | Subsequent Event [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Drawings on credit facility |  | $ 650,000,000 |  |  |
Duke Energy Florida [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances |  |  | $ 1,000,000,000 |  | 1,300,000,000
Duke Energy Florida [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Florida [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 650,000,000 |  |
Duke Energy Ohio [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances |  |  |  |  | $ 100,000,000
Duke Energy Ohio [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Ohio [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 450,000,000 |  |
Duke Energy Indiana [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.65 |  |
Duke Energy Indiana [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 600,000,000 |  |
Piedmont Natural Gas [Member] | Maximum [Member] |  |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Debt to total capitalization percentage, for each borrower |  |  | 0.7 |  |
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | $ 500,000,000 |  |
Piedmont Natural Gas [Member] | June 2017 Piedmont Term Loan Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Facility Size |  |  | 350,000,000 | $ 250,000,000 |
Long-term Line of Credit |  |  | 350,000,000 |  |
Term Loan Proceeds |  |  | 350,000,000 |  |
USDOJ [Member] | North Carolina Ash Basins [Member] | Duke Energy Carolinas [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Minimum Master Credit Facility Balance required |  |  | 250,000,000 |  |
USDOJ [Member] | North Carolina Ash Basins [Member] | Duke Energy Progress [Member] | Revolving Credit Facility [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Minimum Master Credit Facility Balance required |  |  | $ 250,000,000 |  |
January 2019 First Mortgage Bonds [Member] | Duke Energy Ohio [Member] | Subsequent Event [Member] | First Mortgage [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt issuances | $ 800,000,000 |  |  |  |
Restrictive Debt Covenants [Abstract] |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond | $ 450,000,000 |  |  |  |
January 2019 First Mortgage Bonds, 3.65% Interest [Member] | Duke Energy Ohio [Member] | Subsequent Event [Member] | First Mortgage [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate | 3.65% |  |  |  |
Debt issuances | $ 400,000,000 |  |  |  |
Debt Instrument, Term | 10 years |  |  |  |
January 2019 First Mortgage Bonds, 4.30% Interest [Member] | Duke Energy Ohio [Member] | Subsequent Event [Member] | First Mortgage [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate | 4.30% |  |  |  |
Debt issuances | $ 400,000,000 |  |  |  |
Debt Instrument, Term | 30 years |  |  |  |

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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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