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Regulatory Matters (Narrative) (Details) customer in Millions, $ in Millions |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 03, 2018 | Jul. 31, 2018 USD ($) | Sep. 30, 2018 USD ($) customer | Jul. 31, 2018 USD ($) | May 31, 2018 USD ($) | Feb. 28, 2018 USD ($) | Jun. 30, 2017 USD ($) | Dec. 31, 2015 USD ($) | Sep. 30, 2018 USD ($) customer | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) customer MW | Sep. 30, 2017 USD ($) | Dec. 31, 2017 USD ($) | Jun. 30, 2018 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | $ 1,584.0 | $ 1,476.0 | $ 4,592.0 | $ 4,385.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 124.0 | 207.0 | 339.0 | 216.0 |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (1,230.0) | (1,321.0) | (2,640.0) | (3,400.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 319.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | $ 89,865.0 |  |  |  |  |  | 89,865.0 |  | 89,865.0 |  | $ 86,391.0 |
Regulated operating revenue, electric, non-nuclear |  |  |  |  |  |  |  |  | 6,216.0 | 6,091.0 | $ 16,678.0 | 16,122.0 |  |
Generation Facilities To Be Retired [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capacity (in MW) | MW |  |  |  |  |  |  |  |  |  |  | 1,631 |  |  |
Public utilities, property, plant and equipment, net |  |  | $ 355.0 |  |  |  |  |  | $ 355.0 |  | $ 355.0 |  |  |
Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  | 47.00% |  |  |  |  |  | 47.00% |  | 47.00% |  |  |
Long-term purchase commitment, period |  |  |  |  |  |  |  |  |  |  | 20 years |  |  |
Sabal Trail Transmission Pipeline [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | $ 3,200.0 |  |  |  |  |  | $ 3,200.0 |  | $ 3,200.0 |  |  |
Joint owner ownership percentage |  |  | 7.50% |  |  |  |  |  | 7.50% |  | 7.50% |  |  |
Long-term purchase commitment, period |  |  |  |  |  |  |  |  |  |  | 25 years |  |  |
Constitution Pipeline [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  | 24.00% |  |  |  |  |  | 24.00% |  | 24.00% |  |  |
Estimated contributions |  |  | $ 229.0 |  |  |  |  |  | $ 229.0 |  | $ 229.0 |  |  |
Equity method investment, OTTI |  |  |  |  |  |  |  |  |  |  | $ 55.0 |  |  |
Dominion Resources [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  | 48.00% |  |  |  |  |  | 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% |  | 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% |  | 50.00% |  |  |
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint owner ownership percentage |  |  | 42.50% |  |  |  |  |  | 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% |  | 41.00% |  |  |
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | $ 6,500.0 |  |  |  |  |  | $ 6,500.0 |  | $ 6,500.0 |  |  | $ 6,000.0
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | $ 7,000.0 |  |  |  |  |  | $ 7,000.0 |  | $ 7,000.0 |  |  | $ 6,500.0
Hurricane Florence Storm Damage [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Customers experiencing outages | customer |  |  | 1.8 |  |  |  |  |  | 1.8 |  | 1.8 |  |  |
Operation, maintenance and other |  |  | $ 455.0 |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | 85.0 |  |  |  |  |  | $ 85.0 |  | $ 85.0 |  |  |
FERC 494 Refund of Regional Transmission Enhancement Projects [Member] | FERC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Customer refundable fees, refund payments |  |  |  |  |  |  |  |  |  |  | 47.0 |  |  |
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] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 514.0 | 494.0 | 1,464.0 | 1,472.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 1.0 |  | 191.0 |  |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (641.0) | (695.0) | (1,204.0) | (1,531.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 133.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 28,550.0 |  |  |  |  |  | 28,550.0 |  | 28,550.0 |  | 27,876.0 |
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 |  | 650.0 |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ 600.0 |  |  |
Joint owner ownership percentage |  |  | 13.00% |  |  |  |  |  | 13.00% |  | 13.00% |  |  |
Duke Energy Carolinas [Member] | Hurricane Florence Storm Damage [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  | $ 35.0 |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | 10.0 |  |  |  |  |  | $ 10.0 |  | $ 10.0 |  |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  | $ 4.0 |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ 647.0 |  |  |
Requested rate increase, percentage |  |  |  |  |  |  |  |  |  |  | 13.60% |  |  |
Requested return on equity, percent |  |  |  |  |  |  |  |  |  |  | 9.90% |  |  |
Public utilities, requested equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 52.00% |  |  |
Public utilities, requested debt capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 48.00% |  |  |
Penalty assessed |  |  |  |  |  |  |  |  |  |  | $ 70.0 |  |  |
Estimated future coal ash costs |  |  | 201.0 |  |  |  |  |  | 201.0 |  | 201.0 |  |  |
Utilities operating expenses, impairments |  |  |  |  |  |  |  |  | 150.0 |  |  |  |  |
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 assets |  |  | 554.0 |  |  |  |  |  | 554.0 |  | $ 554.0 |  |  |
Regulatory asset, amortization period |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |
Duke Energy Carolinas [Member] | 2017 North Carolina Rate Case [Member] | NCUC [Member] | Deferred Project Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  | 347.0 |  |  |  |  |  | 347.0 |  | $ 347.0 |  |  |
Regulatory asset, amortization period |  |  |  |  |  |  |  |  |  |  | 12 years |  |  |
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 expenses, 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] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  | $ 33.0 |  |  |  |  |  |  |  |  |  |
Progress Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 680.0 | 588.0 | 1,913.0 | 1,697.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 1.0 | 135.0 | 34.0 | 137.0 |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (500.0) | (484.0) | (1,096.0) | (1,205.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 168.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 33,558.0 |  |  |  |  |  | 33,558.0 |  | 33,558.0 |  | 31,887.0 |
Duke Energy Progress [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 431.0 | 365.0 | 1,187.0 | 1,069.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  |  |  | 33.0 |  |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (272.0) | (360.0) | (652.0) | (809.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 145.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 19,995.0 |  |  |  |  |  | 19,995.0 |  | $ 19,995.0 |  | 19,101.0 |
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capacity (in MW) | MW |  |  |  |  |  |  |  |  |  |  | 376 |  |  |
Public utilities, property, plant and equipment, net |  |  | 352.0 |  |  |  |  |  | 352.0 |  | $ 352.0 |  | 385.0 |
Duke Energy Progress [Member] | Hurricane Florence Storm Damage [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  | 420.0 |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | 75.0 |  |  |  |  |  | 75.0 |  | 75.0 |  |  |
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, percent |  |  |  |  |  |  |  |  |  |  | 9.90% |  |  |
Public utilities, requested equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 52.00% |  |  |
Public utilities, requested debt capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 48.00% |  |  |
Penalty assessed |  |  |  |  |  |  |  |  |  |  | $ 30.0 |  |  |
Estimated future coal ash costs |  |  | 129.0 |  |  |  |  |  | 129.0 |  | 129.0 |  |  |
Utilities operating expenses, impairments |  |  |  |  |  |  |  |  |  |  |  |  | 25.0 |
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 |  | $ 116.0 |  |  |
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 assets |  |  | 234.0 |  |  |  |  |  | 234.0 |  | $ 234.0 |  |  |
Regulatory asset, amortization period |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |
Excluded deferred coal ash costs |  |  | 9.5 |  |  |  |  |  | 9.5 |  | $ 9.5 |  |  |
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] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost |  |  | 893.0 |  |  |  |  |  | 893.0 |  | $ 893.0 |  |  |
Regulatory asset, amortization period |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |
Duke Energy Progress [Member] | Shearon Harris Nuclear Expansion [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  |  |  |  |  | 47.0 |
Regulatory asset, amortization period |  |  |  |  |  |  |  |  |  |  | 8 years |  |  |
Wholesale debt return amortization period |  |  |  |  |  |  |  |  |  |  | 15 years |  |  |
Duke Energy Progress [Member] | 2018 PSCSC Petitions [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] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 245.0 | 220.0 | 719.0 | 623.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 1.0 | 135.0 | 1.0 | 137.0 |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (286.0) | (184.0) | (614.0) | (576.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 23.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 13,561.0 |  |  |  |  |  | 13,561.0 |  | 13,561.0 |  | 12,783.0 |
Duke Energy Florida [Member] | Storm Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  | 258.0 |  |  |  |  |  | 258.0 |  | 258.0 |  |  |
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 |  | $ 1,500.0 |  |  |
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Customers experiencing outages | customer |  |  | 1.3 |  |  |  |  |  | 1.3 |  | 1.3 |  |  |
Estimated storm costs - capital and operation maintenance |  |  | $ 510.0 |  |  |  |  |  | $ 510.0 |  | $ 510.0 |  |  |
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 savings |  |  |  |  |  |  |  |  |  |  | 84.0 |  |  |
Tax act excess deferred tax amortization requested rate decrease, amount |  |  |  |  |  |  |  |  |  |  | 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 |  | 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 |  | 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 Florida [Member] | 2017 Second Revised and Restated Stipulation and Settlement Agreement [Member] | Hamilton Project [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | $ (15.2) |  |  |  |  |  |  |  |  |  |  |  |
Duke Energy Florida [Member] | 2017 Second Revised and Restated Stipulation and Settlement Agreement [Member] | Columbia Project [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount |  | $ (14.0) |  |  |  |  |  |  |  |  |  |  |  |
Duke Energy Ohio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 76.0 | 125.0 | 337.0 | 388.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  |  |  |  | 1.0 |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (119.0) | (84.0) | (144.0) | (195.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 3.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 6,493.0 |  |  |  |  |  | 6,493.0 |  | 6,493.0 |  | 6,041.0 |
Regulated operating revenue, electric, non-nuclear |  |  |  |  |  |  |  |  | 373.0 | 371.0 | 1,055.0 | 1,036.0 |  |
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, percent |  |  |  |  |  |  |  |  |  |  | 10.40% |  |  |
Public utilities, requested equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 50.75% |  |  |
Public utilities, requested debt capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 49.25% |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ (20.0) |  |  |
Requested rate increase (decrease), amended amount |  |  |  |  |  |  |  |  |  |  | $ (19.0) |  |  |
Requested rate increase (decrease) amended, percentage |  |  |  |  |  |  |  |  |  |  | 9.84% |  |  |
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, percent |  |  |  |  |  |  |  |  |  |  | 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, percent |  |  |  |  |  |  |  |  |  |  | 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] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost excluding AFUDC |  |  | 163.0 |  |  |  |  |  | 163.0 |  | 163.0 |  |  |
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | OPSB [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated capital cost excluding AFUDC |  |  | 245.0 |  |  |  |  |  | 245.0 |  | 245.0 |  |  |
Duke Energy Ohio [Member] | Duke Energy Kentucky Electric Rate Case [Member] | KPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ 49.0 |  |  |
Requested rate increase, percentage |  |  |  |  |  |  |  |  |  |  | 15.00% |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ 8.4 |  |  |
Requested rate increase (decrease), amended amount |  |  |  |  |  |  |  |  |  |  | $ (30.1) |  |  |
Requested rate increase (decrease) amended, percentage |  |  |  |  |  |  |  |  |  |  | 9.00% |  |  |
Approved return on equity percentage |  |  |  |  |  |  |  |  |  |  | 9.725% |  |  |
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  | 49.00% |  |  |
Total allocable capitalization |  |  | 650.0 |  |  |  |  |  | 650.0 |  | $ 650.0 |  |  |
Incremental rider revenue |  |  |  |  |  |  |  |  |  |  | 13.0 |  |  |
Duke Energy Ohio [Member] | Duke Energy Kentucky Gas Base Rate Case [Member] | KPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | $ 10.5 |  |  |
Requested rate increase, percentage |  |  |  |  |  |  |  |  |  |  | 11.10% |  |  |
Requested rate increase (decrease), amended amount |  |  |  |  |  |  |  |  |  |  | $ (5.2) |  |  |
Duke Energy Indiana [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 198.0 | 177.0 | 576.0 | 546.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 30.0 |  | 30.0 |  |  |
Loss before income taxes |  |  |  |  |  |  |  |  | (154.0) | (196.0) | (421.0) | (521.0) |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  | 22.0 |  |  |
Public utilities, property, plant and equipment, net |  |  | 10,467.0 |  |  |  |  |  | 10,467.0 |  | 10,467.0 |  | 10,286.0 |
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] | Edwardsport Integrated Gasification Combined Cycle Plant [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  |  | (10.0) |  |  |
Impairment and related charges |  |  |  |  |  |  |  |  | 32.0 |  |  |  |  |
Decrease in regulatory assets |  |  |  |  |  |  |  |  |  |  | $ 30.0 |  |  |
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, percent |  |  |  |  |  |  |  |  |  |  | 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, percent |  |  |  |  |  |  |  |  |  |  | 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] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operation, maintenance and other |  |  |  |  |  |  |  |  | 85.0 | 73.0 | 252.0 | 226.0 |  |
Impairment and related charges |  |  |  |  |  |  |  |  |  |  |  | 7.0 |  |
Loss before income taxes |  |  |  |  |  |  |  |  | 32.0 | $ 21.0 | (102.0) | $ (119.0) |  |
Public utilities, property, plant and equipment, net |  |  | 5,712.0 |  |  |  |  |  | 5,712.0 |  | 5,712.0 |  | $ 5,246.0 |
Piedmont Natural Gas [Member] | NCUC IMR Petition filed October 2018 [Member] | NCUC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  | (9.5) |  |  |  |  |
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) |  |  |  |  |
Storm Costs [Member] | Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allowed storm allowance |  |  | $ 132.0 |  |  |  |  |  | $ 132.0 |  | $ 132.0 |  |  |
Subsequent Event [Member] | Piedmont Natural Gas [Member] | South Carolina Rate Stabilization Adjustment Filing [Member] | PSCSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity percentage | 10.20% |  |  |  |  |  |  |  |  |  |  |  |  |

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