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%