Regulatory Matters (Narrative) (Details) Customers in Millions, $ in Millions			1 Months Ended			3 Months Ended		12 Months Ended
	Apr. 13, 2018 USD ($)	Apr. 02, 2018 USD ($)	Feb. 28, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2018 USD ($) Customers MW	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 1,464.0	$ 1,468.0
Public Utilities, Property, Plant and Equipment, Net						87,373.0		$ 86,391.0
Loss Before Income Taxes						(803.0)	(1,061.0)
Electric Domestic Regulated Revenue						5,284.0	4,913.0
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net						$ 391.0
Capacity (in MW) | MW						1,738
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						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%
Estimated capital cost						$ 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%
Estimated Contributions						$ 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%
Southern Company Gas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						5.00%
Spectra Energy Partners [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						50.00%
NextEra Energy [Member] | Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						42.50%
Williams Partners L.P. [Member] | Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage						41.00%
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost						$ 6,000.0
Original estimated capital cost						5,000.0
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost						6,500.0
Original estimated capital cost						5,500.0
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						451.0	495.0
Public Utilities, Property, Plant and Equipment, Net						28,158.0		27,876.0
Loss Before Income Taxes						(414.0)	(418.0)
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
Joint owner ownership percentage						13.00%
Duke Energy Carolinas [Member] | William State Lee III Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Net						$ 558.0
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
Requested Rate Increase (Decrease), Amended, Amount						$ 472.0
Loss Before Income Taxes						14.0
Duke Energy Carolinas [Member] | FERC Formula Rate Matter [Member] | FERC [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refundable Fees, Refund Payments						25.0
Progress Energy [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						623.0	560.0
Public Utilities, Property, Plant and Equipment, Net						32,254.0		31,887.0
Loss Before Income Taxes						(273.0)	(305.0)
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						381.0	362.0
Public Utilities, Property, Plant and Equipment, Net						19,253.0		19,101.0
Loss Before Income Taxes						(206.0)	(223.0)
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						$ 365.0		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
Utilities Operating Expense, Impairments								25.0
Penalty assessed						30.0
Estimated future coal ash costs						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
Regulatory Assets						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
Asset Retirement Obligation, 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
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 Florida [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 237.0	195.0
Public Utilities, Property, Plant and Equipment, Net						12,998.0		12,783.0
Loss Before Income Taxes						(123.0)	(142.0)
Duke Energy Florida [Member] | Storm Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets						338.0
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
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Storm Costs - Capital and Operation Maintenance						$ 513.0
Customers Experiencing Outages | Customers						1.3
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member] | Subsequent Event [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						$ 131.0	131.0
Public Utilities, Property, Plant and Equipment, Net						6,163.0		6,041.0
Loss Before Income Taxes						37.0	(65.0)
Electric Domestic Regulated Revenue						336.0	337.0
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%
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%
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | Subsequent Event [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage	9.84%
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)
Duke Energy Ohio [Member] | 2017 Ohio Electric Base Rate Case [Member] | Subsequent Event [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rider Revenue Increase	10.0
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Electric Domestic Regulated Revenue					$ 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
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%
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | Subsequent Event [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
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
Costs recovered through existing riders	50.0
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						$ 181.0	176.0
Public Utilities, Property, Plant and Equipment, Net						10,345.0		10,286.0
Loss Before Income Taxes						$ (135.0)	(150.0)
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%
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses						$ 82.0	77.0
Public Utilities, Property, Plant and Equipment, Net						5,361.0		$ 5,246.0
Loss Before Income Taxes						(145.0)	$ (153.0)
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