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Regulatory Matters (Narrative) (Details) Customers in Millions, $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jul. 31, 2018 USD ($) | May 31, 2018 USD ($) | Feb. 28, 2018 USD ($) | Jun. 30, 2017 USD ($) | Dec. 31, 2015 USD ($) | Jun. 30, 2018 USD ($) Customers | Jun. 30, 2017 USD ($) | Jun. 30, 2018 USD ($) Customers MW | Jun. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | $ 1,544.0 | $ 1,441.0 | $ 3,008.0 | $ 2,909.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 88,495.0 |  | 88,495.0 |  | $ 86,391.0
Regulated Operating Revenue, Electric, Non-Nuclear |  |  |  |  |  | 5,178.0 | 5,118.0 | 10,462.0 | 10,031.0 |
Accretion expense |  |  |  |  |  |  |  | 212.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (607.0) | (1,018.0) | (1,410.0) | (2,079.0) |
Generation Facilities To Be Retired [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | $ 387.0 |  | $ 387.0 |  |
Capacity (in MW) | MW |  |  |  |  |  |  |  | 1,738 |  |
Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 47.00% |  | 47.00% |  |
Long-term Purchase Commitment, Period |  |  |  |  |  |  |  | 20 years |  |
Sabal Trail Transmission Pipeline [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 7.50% |  | 7.50% |  |
Estimated capital cost |  |  |  |  |  | $ 3,200.0 |  | $ 3,200.0 |  |
Long-term Purchase Commitment, Period |  |  |  |  |  |  |  | 25 years |  |
Constitution Pipeline [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 24.00% |  | 24.00% |  |
Estimated Contributions |  |  |  |  |  | $ 229.0 |  | $ 229.0 |  |
Equity Method Investment, Other than Temporary Impairment |  |  |  |  |  |  |  | $ 55.0 |  |
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 48.00% |  | 48.00% |  |
Southern Company Gas [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 5.00% |  | 5.00% |  |
Spectra Energy Partners [Member] | Sabal Trail Transmission Pipeline [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 50.00% |  | 50.00% |  |
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 42.50% |  | 42.50% |  |
Williams Partners L.P. [Member] | Constitution Pipeline [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  |  |  |  | 41.00% |  | 41.00% |  |
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  |  |  |  | $ 6,000.0 |  | $ 6,000.0 |  |
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  |  |  |  | 6,500.0 |  | 6,500.0 |  |
Progress Energy Merger FERC Mitigation [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Penalty assessed |  |  |  |  |  |  |  | 3.5 |  |
Duke Energy Carolinas [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 499.0 | 483.0 | 950.0 | 978.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 28,181.0 |  | 28,181.0 |  | 27,876.0
Accretion expense |  |  |  |  |  |  |  | 89.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (149.0) | (418.0) | (563.0) | (836.0) |
Duke Energy Carolinas [Member] | William States Lee Combined Cycle Facility [Member] | NCEMC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated capital cost of new utility plant, including AFUDC |  |  |  |  |  | $ 650.0 |  | $ 650.0 |  |
Joint owner ownership percentage |  |  |  |  |  | 13.00% |  | 13.00% |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 600.0 |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 647.0 |  |
Requested Rate Increase, Percentage |  |  |  |  |  |  |  | 13.60% |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 9.90% |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  |  |  |  |  | 52.00% |  |
Public Utilities, Requested Debt Capital Structure, Percentage |  |  |  |  |  |  |  | 48.00% |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  | $ 4.0 |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  |  |  | $ 150.0 |  |  |  |
Penalty assessed |  |  |  |  |  |  |  | $ 70.0 |  |
Estimated future coal ash costs |  |  |  |  |  | 201.0 |  | 201.0 |  |
Loss Before Income Taxes |  |  |  |  |  |  |  | $ 14.0 |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Asset retirement obligations - coal ash [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 5 years |  |
Regulatory Assets |  |  |  |  |  | 554.0 |  | $ 554.0 |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Deferred Project Costs [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 12 years |  |
Regulatory Assets |  |  |  |  |  | 347.0 |  | $ 347.0 |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | William State Lee Iii Nuclear Station [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  |  |  |  |  | 29.0 |  |
Duke Energy Carolinas [Member] | FERC Formula Rate Matter [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Customer Refundable Fees, Refund Payments |  |  |  |  |  |  |  | 25.0 |  |
Duke Energy Carolinas [Member] | 2018 Sale of Hydro Plants [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated loss on Asset Sale |  | $ 40.0 |  |  |  |  |  |  |  |
Duke Energy Carolinas [Member] | 2018 PSCSC Petitions [Member] | Subsequent Event [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount | $ 33.0 |  |  |  |  |  |  |  |  |
Progress Energy [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 610.0 | 549.0 | 1,233.0 | 1,109.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 32,894.0 |  | 32,894.0 |  | 31,887.0
Accretion expense |  |  |  |  |  |  |  | 113.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (323.0) | (416.0) | (596.0) | (721.0) |
Duke Energy Progress [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 375.0 | 342.0 | 756.0 | 704.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 19,617.0 |  | 19,617.0 |  | 19,101.0
Accretion expense |  |  |  |  |  |  |  | 97.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (174.0) | (226.0) | (380.0) | (449.0) |
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 344.0 |  | $ 344.0 |  | 385.0
Capacity (in MW) | MW |  |  |  |  |  |  |  | 376 |  |
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 477.0 |  |
Requested Rate Increase, Percentage |  |  |  |  |  |  |  | 14.90% |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 9.90% |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  |  |  |  |  | 52.00% |  |
Public Utilities, Requested Debt Capital Structure, Percentage |  |  |  |  |  |  |  | 48.00% |  |
Requested Rate Increase (Decrease), Amended, Amount |  |  |  |  |  |  |  | $ 420.0 |  |
Requested Rate Increase (Decrease), Amended, Percentage |  |  |  |  |  |  |  | 13.00% |  |
Estimated Storm Costs - Capital and Operation Maintenance |  |  |  |  |  | 116.0 |  | $ 116.0 |  |
Utilities Operating Expense, Impairments |  |  |  |  |  |  |  |  |  | 25.0
Penalty assessed |  |  |  |  |  |  |  | 30.0 |  |
Estimated future coal ash costs |  |  |  |  |  | 129.0 |  | 129.0 |  |
Loss Before Income Taxes |  |  |  |  |  |  |  | $ 68.0 |  |
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Asset retirement obligations - coal ash [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 5 years |  |
Excluded deferred coal ash costs |  |  |  |  |  | 9.5 |  | $ 9.5 |  |
Regulatory Assets |  |  |  |  |  | 234.0 |  | 234.0 |  |
Duke Energy Progress [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Storm Costs [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 80.0 |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 5 years |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 51.0 |  |
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 56.0 |  |
Accretion expense |  |  |  |  |  |  |  |  |  | 18.5
Approved return on equity percentage |  |  |  |  |  |  |  | 10.10% |  |
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 1 Increase [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 38.0 |  |
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 2 Increase [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 18.5 |  |
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 10 years |  |
Estimated capital cost |  |  |  |  |  | 893.0 |  | $ 893.0 |  |
Duke Energy Progress [Member] | Shearon Harris Nuclear Expansion [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Asset, Amortization Period |  |  |  |  |  |  |  | 8 years |  |
Wholesale Debt Return Amortization Period |  |  |  |  |  |  |  | 15 years |  |
Regulatory Assets |  |  |  |  |  |  |  |  |  | 47.0
Duke Energy Progress [Member] | 2018 PSCSC Petitions [Member] | Subsequent Event [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount | $ 20.0 |  |  |  |  |  |  |  |  |
Duke Energy Progress [Member] | FERC Form 1 Reporting Matter [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Customer Refundable Fees, Refund Payments |  |  |  |  |  |  |  | $ 14.0 |  |
Duke Energy Florida [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 237.0 | 208.0 | 474.0 | 403.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 13,274.0 |  | 13,274.0 |  | 12,783.0
Accretion expense |  |  |  |  |  |  |  | 16.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (205.0) | (250.0) | (328.0) | (392.0) |
Duke Energy Florida [Member] | Storm Costs [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  |  |  |  |  | 295.0 |  | 295.0 |  |
Duke Energy Florida [Member] | Citrus County Station [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated capital cost of new utility plant, including AFUDC |  |  |  |  |  | 1,500.0 |  | 1,500.0 |  |
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated Storm Costs - Capital and Operation Maintenance |  |  |  |  |  | $ 510.0 |  | $ 510.0 |  |
Customers Experiencing Outages | Customers |  |  |  |  |  | 1.3 |  | 1.3 |  |
Duke Energy Florida [Member] | Federal Tax Act Impacts [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ (151.0) |  |
Tax Act Annual Tax Savings |  |  |  |  |  |  |  | 84.0 |  |
Tax Act Excess Deferred Tax Amortization |  |  |  |  |  |  |  | 67.0 |  |
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 201.0 |  |
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | FPSC [Member] | Storm Costs [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory Assets |  |  |  |  |  | $ 151.0 |  | 151.0 |  |
Duke Energy Florida [Member] | Federal Tax Act Impacts Revenue Requirement [Member] | Crystal River Units 3 and 4 [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 50.0 |  | 50.0 |  |
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 200.0 |  |
Duke Energy Ohio [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 130.0 | 132.0 | 261.0 | 263.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 6,328.0 |  | 6,328.0 |  | 6,041.0
Regulated Operating Revenue, Electric, Non-Nuclear |  |  |  |  |  | 346.0 | 328.0 | 682.0 | 665.0 |
Accretion expense |  |  |  |  |  |  |  | 2.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (62.0) | (46.0) | (25.0) | (111.0) |
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 15.0 |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 10.40% |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  |  |  |  |  | 50.75% |  |
Public Utilities, Requested Debt Capital Structure, Percentage |  |  |  |  |  |  |  | 49.25% |  |
Requested Rate Increase (Decrease), Amended, Amount |  |  |  |  |  |  |  | $ (19.0) |  |
Requested Rate Increase (Decrease), Amended, Percentage |  |  |  |  |  |  |  | 9.84% |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ (20.0) |  |
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ (18.0) |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 9.22% |  |
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | PUCO [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ (29.0) |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 10.24% |  |
Requested Rider Revenue Increase |  |  |  |  |  |  |  | $ 10.0 |  |
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Regulated Operating Revenue, Electric, Non-Nuclear |  |  |  |  | $ 20.0 |  |  |  |  |
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 38.0 |  |
Approved Rate Increase (Decrease), One Time Waiver Amount |  |  |  |  |  |  |  | 56.0 |  |
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated Capital Cost Excluding AFUDC |  |  |  |  |  | 112.0 |  | 112.0 |  |
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | KPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 49.0 |  |
Requested Rate Increase, Percentage |  |  |  |  |  |  |  | 15.00% |  |
Requested Rate Increase (Decrease), Amended, Amount |  |  |  |  |  |  |  | $ (30.1) |  |
Requested Rate Increase (Decrease), Amended, Percentage |  |  |  |  |  |  |  | 9.00% |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ 8.4 |  |
Approved return on equity percentage |  |  |  |  |  |  |  | 9.725% |  |
Public Utilities, Approved Equity Capital Structure, Percentage |  |  |  |  |  |  |  | 49.00% |  |
Total Allocable Capitalization |  |  |  |  |  | 650.0 |  | $ 650.0 |  |
Incremental Rider Revenue |  |  |  |  |  |  |  | 13.0 |  |
Duke Energy Indiana [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 197.0 | 194.0 | 378.0 | 369.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 10,446.0 |  | 10,446.0 |  | 10,286.0
Accretion expense |  |  |  |  |  |  |  | 14.0 |  |
Loss Before Income Taxes |  |  |  |  |  | (132.0) | (175.0) | $ (267.0) | (325.0) |
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Litigation Settlement, Amount Awarded to Other Party |  |  |  | $ 29.0 |  |  |  |  |  |
Duke Energy Indiana [Member] | FERC Transmission Rates [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved return on equity percentage |  |  |  |  |  |  |  | 12.38% |  |
Approved Return on Equity Percentage Adder |  |  |  |  |  |  |  | 0.50% |  |
Duke Energy Indiana [Member] | FERC Complaint [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 8.67% |  |
Duke Energy Indiana [Member] | FERC Complaint 1 [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved return on equity percentage |  |  |  |  |  |  |  | 10.32% |  |
Duke Energy Indiana [Member] | FERC Complaint 2 [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Return on Equity, Percentage |  |  |  |  |  |  |  | 9.70% |  |
Duke Energy Indiana [Member] | Federal Tax Act Impacts Tranche 1 [Member] | IURC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | $ (7.0) |  |
Duke Energy Indiana [Member] | Federal Tax Act Impacts Tranche 2 [Member] | IURC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | (35.0) |  |
Piedmont Natural Gas [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses |  |  |  |  |  | 85.0 | 76.0 | 167.0 | 153.0 |
Public Utilities, Property, Plant and Equipment, Net |  |  |  |  |  | 5,556.0 |  | 5,556.0 |  | $ 5,246.0
Loss Before Income Taxes |  |  |  |  |  | 11.0 | $ 13.0 | (134.0) | $ (140.0) |
Piedmont Natural Gas [Member] | NCUC IMR Petition filed May 2018 [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Approved Rate Increase (Decrease), Amount |  |  |  |  |  | (5.7) |  |  |  |
Piedmont Natural Gas [Member] | TPUC IMR Petition Filed November 2017 [Member] | TPUC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 3.3 |  |
Requested Rate Increase (Decrease), Amended, Amount |  |  |  |  |  |  |  | 0.4 |  |
Storm Costs [Member] | Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Allowed Storm Reserve |  |  |  |  |  | $ 132.0 |  | $ 132.0 |  |

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