Regulatory Matters (Narrative) (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 17, 2017 USD ($)	Jun. 30, 2016 USD ($)
Public Utilities, General Disclosures [Line Items]
Net Asset Percentage Limit			25.00%
Regulatory assets, noncurrent			$ 12,442,000,000	$ 12,878,000,000
Net property, plant and equipment			86,391,000,000	82,520,000,000
Regulatory assets			13,879,000,000	13,901,000,000
Impairment charges			282,000,000	18,000,000	$ 106,000,000
Debt Instrument, Face Amount			6,070,000,000	9,127,000,000
Regulated Revenue			21,177,000,000	21,221,000,000	21,379,000,000
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 397,000,000
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			$ 3,200,000,000
Long-term Purchase Commitment, Period			25 years
Constitution Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage			24.00%
Estimated Contributions			$ 229,000,000
Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			64,000,000	66,000,000
Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			2,249,000,000	2,387,000,000
Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			480,000,000	534,000,000
NCEMPA deferrals [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			53,000,000	51,000,000
Nuclear asset securitized balance, net [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			1,142,000,000	1,193,000,000
Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			119,000,000	226,000,000
Minimum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			6,000,000,000
Original estimated capital cost			5,000,000,000
Maximum [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			6,500,000,000
Original estimated capital cost			$ 5,500,000,000
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%
Enbridge Inc. [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%
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 2,853,000,000	3,159,000,000
Net property, plant and equipment			27,876,000,000	26,762,000,000
Regulatory assets			3,152,000,000	3,397,000,000
Impairment charges				1,000,000	1,000,000
Debt Instrument, Face Amount			$ 550,000,000	1,600,000,000
Duke Energy Carolinas [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Long-term Purchase Commitment, Period			20 years
Duke Energy Carolinas [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 410,000,000	481,000,000
Duke Energy Carolinas [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			29,000,000	39,000,000
Duke Energy Carolinas [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			84,000,000	92,000,000
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			$ 600,000,000
Joint owner ownership percentage			13.00%
Duke Energy Carolinas [Member] | William State Lee III Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 558,000,000
Duke Energy Carolinas [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 647,000,000
Requested Rate Increase (Decrease), Percentage			13.60%
Duke Energy Carolinas [Member] | 2017 NC Rate Case [Member] | Subsequent Event [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount		$ (290,000,000)
Duke Energy Carolinas [Member] | Advanced Metering Infrastructure Deferral [Member] | PSCSC [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 45,000,000
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			3,507,000,000	3,243,000,000
Net property, plant and equipment			19,101,000,000	18,387,000,000
Regulatory assets			3,859,000,000	3,431,000,000
Impairment charges			19,000,000	1,000,000	5,000,000
Debt Instrument, Face Amount			$ 800,000,000	450,000,000
Duke Energy Progress [Member] | Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Long-term Purchase Commitment, Period			20 years
Duke Energy Progress [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 430,000,000	423,000,000
Duke Energy Progress [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			170,000,000	165,000,000
Duke Energy Progress [Member] | NCEMPA deferrals [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			53,000,000	51,000,000
Duke Energy Progress [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			35,000,000	38,000,000
Duke Energy Progress [Member] | Asheville Plant [Member] | Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			$ 385,000,000	492,000,000
Capacity (in MW) | MW			376
Duke Energy Progress [Member] | Shearon Harris Nuclear Station [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 47,000,000
Wholesale Debt Return Amortization Period			15 years
Regulatory Noncurrent Asset, Amortization Period			8 years
Duke Energy Progress [Member] | 2017 NC Rate Case [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 477,000,000
Requested Rate Increase (Decrease), Percentage			14.90%
Requested Rate Increase (Decrease), Amended, Amount			$ 420,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage			13.00%
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, Impairments			$ 25,000,000
Duke Energy Progress [Member] | 2017 NC Rate Case Unsettled Amount [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amended, Amount			300,000,000
Duke Energy Progress [Member] | Storm Cost Deferrals [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			73,000,000
Deferred Storm and Property Reserve Deficiency, Noncurrent			74,000,000
Duke Energy Progress [Member] | Storm Cost Deferrals [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Storm Costs - Capital and Operation Maintenance			116,000,000
Regulatory assets			77,000,000
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 56,000,000
Approved return on equity percentage amount by state commission			10.10%
Regulatory Noncurrent Asset, Amortization Period			15 years
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 by state commission			$ 38,000,000
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 by state commission			18,500,000
Duke Energy Progress [Member] | 2016 South Carolina Rate Case Settlement Year 2 Offset [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			(18,500,000)
Duke Energy Progress [Member] | Western Carolinas Modernization Plan [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			893,000,000
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			2,503,000,000	2,480,000,000
Net property, plant and equipment			12,783,000,000	11,790,000,000
Regulatory assets			2,892,000,000	2,693,000,000
Impairment charges			138,000,000	6,000,000	7,000,000
Debt Instrument, Face Amount			1,300,000,000	1,894,000,000
Duke Energy Florida [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			476,000,000	458,000,000
Duke Energy Florida [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			216,000,000	257,000,000
Duke Energy Florida [Member] | Nuclear asset securitized balance, net [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			1,142,000,000	1,193,000,000
Duke Energy Florida [Member] | Nuclear Deferral [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets				96,000,000
Duke Energy Florida [Member] | Citrus County Combined Cycle Facility [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC			$ 1,500,000,000
Duke Energy Florida [Member] | Crystal River Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Noncurrent Asset, Amortization Period			20 years
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | ISFSI Projects [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 113,000,000
Approved return on equity percentage amount by state commission			7.35%
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 1,283,000,000				1,283,000,000
Impairment charges					15,000,000
Duke Energy Florida [Member] | Crystal River Unit 3 [Member] | DEFPF [Member]
Public Utilities, General Disclosures [Line Items]
Debt Instrument, Face Amount							$ 1,294,000,000
Proceeds from Issuance of Debt				1,287,000,000
Duke Energy Florida [Member] | Storm Restoration Cost Recovery [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 376,000,000
Customers Experiencing Outages			1,300,000
Estimated Storm Costs - Capital and Operation Maintenance			$ 513,000,000
Allowed Storm Reserve			132,000,000
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			75,000,000
Approved rate increase (decrease) amount by state commission			$ 67,000,000
Approved return on equity percentage amount by state commission			9.50%
Regulatory Noncurrent Asset, Amortization Period			15 years
Impairment charges			$ 135,000,000
Duke Energy Florida [Member] | 2017 Second Revised and Restated Settlement [Member] | FPSC [Member] | Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 196,000,000
Regulatory Noncurrent Asset, Amortization Period			24 months
Duke Energy Florida [Member] | Hines Chiller Uprate Project [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 19,000,000
Estimated capital cost			$ 150,000,000
Duke Energy Florida [Member] | Osprey Energy Center Acquisition [Member] | USDOJ [Member]
Public Utilities, General Disclosures [Line Items]
Other Commitment						$ 600,000
Duke Energy Florida [Member] | 2013 FPSC Settlement Agreement [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			10.50%
Duke Energy Florida [Member] | 2013 FPSC Settlement Agreement [Member] | Crystal River Unit 3 [Member] | Original Uprate Project [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 87,000,000
Regulatory Noncurrent Asset, Amortization Period			7 years
Duke Energy Florida [Member] | Levy Nuclear Project [Member] | Levy Nuclear Station [Member] | FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 82,000,000
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Limit of Total Capital			30.00%
Regulatory assets, noncurrent			$ 445,000,000	520,000,000
Net property, plant and equipment			6,041,000,000	5,547,000,000
Regulatory assets			494,000,000	557,000,000
Impairment charges			1,000,000
Debt Instrument, Face Amount			100,000,000	250,000,000
Regulated Revenue			1,373,000,000	1,410,000,000	1,331,000,000
Duke Energy Ohio [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			139,000,000	135,000,000
Duke Energy Ohio [Member] | RTO Realignment [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 50,000,000	71,000,000
Approved MVP Proposals			17
MISO estimate of Duke Energy Ohio's MVP obligation			$ 2,700,000,000
Duke Energy Ohio [Member] | Duke Energy Kentucky Rate Case [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 49,000,000
Requested Rate Increase (Decrease), Percentage			15.00%
Duke Energy Ohio [Member] | Woodsdale Station Fuel System [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			$ 55,000,000
Duke Energy Ohio [Member] | East Bend Coal Ash Basin Filing [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost			93,000,000
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 15,000,000
Requested Return on Equity, Percentage			10.40%
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ (18,000,000)
Requested Return on Equity, Percentage			9.22%
Duke Energy Ohio [Member] | Electric Base Rate Case [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ (29,000,000)
Requested Return on Equity, Percentage			10.24%
Duke Energy Ohio [Member] | Natural Gas Pipeline Extension [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Capital Cost Excluding AFUDC			$ 110,000,000
Duke Energy Ohio [Member] | Accelerated Natural Gas Service Line Replacement Rider | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Costs Not yet Approved			240,000,000
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery Program [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			56,000,000
Regulated Revenue	$ 20,000,000
Duke Energy Ohio [Member] | Energy Efficiency Cost Recovery Program [Member] | PUCO [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			38,000,000
Duke Energy Ohio [Member] | Mgp Remediation [Member] | East End Site [Member] | PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			35,000,000
Duke Energy Ohio [Member] | Advanced Metering Infrastructure Project [Member] | KPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			6,000,000
Estimated capital cost			$ 49,000,000
Duke Energy Kentucky [Member]
Public Utilities, General Disclosures [Line Items]
Required Equity Capital Structure Percent			35.00%
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			$ 978,000,000	1,073,000,000
Net property, plant and equipment			10,286,000,000	9,924,000,000
Regulatory assets			1,143,000,000	1,222,000,000
Impairment charges			18,000,000	8,000,000	88,000,000
Debt Instrument, Face Amount				500,000,000
Duke Energy Indiana [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			197,000,000	222,000,000
Duke Energy Indiana [Member] | Retired Generation Facilities [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			65,000,000	73,000,000
Duke Energy Indiana [Member] | Benton County Wind Farm Dispute [Member]
Public Utilities, General Disclosures [Line Items]
Litigation Settlement, Amount Awarded to Other Party			29,000,000
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			$ 380,000,000
Federal Mandate Costs Recovered Through Tracker Mechanism			80.00%
Federally Mandated Costs Recovered In Future Rate Case			20.00%
Percentage of Costs Recovered through Existing Rider			60.00%
Percentage Recovered Through Future Rate Case			40.00%
Long-term Debt Rate			4.73%
Duke Energy Indiana [Member] | Coal Combustion Residual Plan [Member] | IURC [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 365,000,000
Duke Energy Indiana [Member] | IGCC Rider Proceeding [Member] | Edwardsport IGCC Plant [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			152,000,000
Approved rate increase (decrease) amount by state commission			$ (87,500,000)
Regulatory Noncurrent Asset, Amortization Period			8 years
Legal Fees			$ 5,500,000
Utilities Operating Expense, Other					$ 93,000,000
Duke Energy Indiana [Member] | FERC Transmission Rates [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			12.38%
Approved Return on Equity Percentage Adder			0.50%
Duke Energy Indiana [Member] | FERC Complaint [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			8.67%
Duke Energy Indiana [Member] | FERC Complaint 1 [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission			10.32%
Duke Energy Indiana [Member] | FERC Complaint 2 [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			9.70%
Duke Energy Indiana [Member] | Grid Infrastructure Improvement Plan [Member] | IURC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 1,400,000,000
Approved return on equity percentage amount by state commission			10.00%
Estimated capital cost			$ 1,800,000,000
Duke Energy Indiana [Member] | Advanced Metering Infrastructure Project [Member]
Public Utilities, General Disclosures [Line Items]
Net property, plant and equipment			21,000,000
Impairment charges			22,000,000	8,000,000
Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			283,000,000	373,000,000
Net property, plant and equipment			5,246,000,000	4,814,000,000
Regulatory assets			378,000,000	497,000,000
Impairment charges			7,000,000
Piedmont Natural Gas [Member] | Regulatory Clause Revenues, under-recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			64,000,000	66,000,000
Piedmont Natural Gas [Member] | Accrued Pension And Post Retirement [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 91,000,000	$ 166,000,000
Piedmont Natural Gas [Member] | South Carolina Rate Stabilization Adjustment Filing [Member] | PSCSC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity, Percentage			12.60%
Approved return on equity percentage amount by state commission			10.20%
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed October 2017 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			$ 8,900,000
Piedmont Natural Gas [Member] | NCUC IMR Petition Filed May 2017 [Member] | NCUC [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount by state commission			11,600,000
Piedmont Natural Gas [Member] | TPUC IMR Petition Filed November 2017 [Member] | TPUC [Member]
Public Utilities, General Disclosures [Line Items]
Requested Rate Increase (Decrease), Amount			3,300,000
Requested Rate Increase (Decrease), Amended, Amount			$ 400,000