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