Regulatory Matters (Regulatory Matters Narrative - Duke Energy Ohio) (Details) $ in Millions				9 Months Ended
	Oct. 08, 2021 USD ($)	Oct. 01, 2021 USD ($)	Jun. 01, 2021 USD ($)	Sep. 30, 2021 USD ($) site	Dec. 31, 2020 USD ($)	Nov. 18, 2020 USD ($) order	Jul. 23, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jan. 01, 2020 plant	Nov. 21, 2019 condition	Jul. 12, 2019 USD ($)	Mar. 29, 2019 USD ($)	Sep. 28, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net				$ 110,236	$ 106,782
Duke Energy Ohio
Public Utilities, General Disclosures [Line Items]
Number of nuclear generating facilities eligible for funding | plant									2
Public utilities, property, plant and equipment, net				8,429	8,009
Duke Energy Ohio | Duke Energy Ohio Electric Base Rate Case | PUCO | Subsequent event
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount		$ 55
Requested return on equity, percent		10.30%
Requested rate increase, percentage		3.30%
Duke Energy Ohio | Energy Efficiency Cost Recovery
Public Utilities, General Disclosures [Line Items]
Number of orders issued on application for rehearing | order						2
Shared savings cap						$ 8
Duke Energy Ohio | Natural Gas Pipeline extension | OPSB | Minimum
Public Utilities, General Disclosures [Line Items]
Estimated capital cost excluding AFUDC				185
Number of conditions on construction | condition										41
Duke Energy Ohio | Natural Gas Pipeline extension | OPSB | Maximum
Public Utilities, General Disclosures [Line Items]
Estimated capital cost excluding AFUDC				$ 205
Duke Energy Ohio | MGP Cost Recovery - 2009 Through 2012 | PUCO
Public Utilities, General Disclosures [Line Items]
Number of environmental remediation sites | site				2
Regulatory assets				$ 55
Duke Energy Ohio | MGP Cost Recovery - 2013 Through 2017 | PUCO
Public Utilities, General Disclosures [Line Items]
Regulatory assets													$ 26
Duke Energy Ohio | MGP Cost Recovery - 2013 Through 2017 | PUCO | MGP Costs - regulatory disallowance
Public Utilities, General Disclosures [Line Items]
Regulatory assets													$ 12
Duke Energy Ohio | MGP Cost Recovery - 2018 | PUCO
Public Utilities, General Disclosures [Line Items]
Regulatory assets												$ 20
Duke Energy Ohio | MGP Cost Recovery - 2018 | PUCO | MGP Costs - regulatory disallowance
Public Utilities, General Disclosures [Line Items]
Regulatory assets											$ 11
Duke Energy Ohio | MGP Cost Recovery - 2019 | PUCO
Public Utilities, General Disclosures [Line Items]
Regulatory assets								$ 39
Duke Energy Ohio | MGP Cost Recovery - 2019 | PUCO | MGP Costs - regulatory disallowance
Public Utilities, General Disclosures [Line Items]
Regulatory assets							$ 4
Duke Energy Ohio | Midwest Propane Caverns
Public Utilities, General Disclosures [Line Items]
Public utilities, property, plant and equipment, net				$ 27	$ 27
Duke Energy Kentucky | Duke Energy Kentucky Gas Base Rate Case | KPSC
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount			$ 15
Requested rate increase, percentage			13.00%
Duke Energy Kentucky | Duke Energy Kentucky Gas Base Rate Case | KPSC | Subsequent event
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount	$ 9
Annual rate increase cap, percentage	5.00%
Base rate case-stay out period	4 years
Duke Energy Kentucky | Duke Energy Kentucky Gas Base Rate Case | KPSC | Subsequent event | Public Utilities, Natural Gas Base Rates
Public Utilities, General Disclosures [Line Items]
Requested rate increase, percentage	9.375%
Duke Energy Kentucky | Duke Energy Kentucky Gas Base Rate Case | KPSC | Subsequent event | Public Utilities, Natural Gas Riders
Public Utilities, General Disclosures [Line Items]
Requested rate increase, percentage	9.30%