Regulatory Matters - Ohio (Details) - OHIO - PUCO $ in Thousands							9 Months Ended
	Aug. 03, 2021 USD ($)	Jun. 16, 2021 USD ($)	Nov. 24, 2020	Jul. 17, 2019 USD ($)	Jul. 15, 2019 USD ($)	Jun. 01, 2016 USD ($)	Sep. 30, 2021 USD ($)	Sep. 13, 2021 requirement	Aug. 06, 2021 USD ($)	Dec. 31, 2020 USD ($)
Regulatory Matters [Line Items]
Proposed goal to reduce CO2 pollution (percent)						90.00%
Energy Conservation, Economic Development and Job Retention
Regulatory Matters [Line Items]
Contribution amount						$ 51,000
Distribution Modernization Rider
Regulatory Matters [Line Items]
Requested plan extension period			2 years
Delivery Capital Recovery Rider
Regulatory Matters [Line Items]
Annual revenue cap for rider for years three through six						20,000
Annual revenue cap for rider for years six through eight						$ 15,000
OCC DMR Refund | The Ohio Companies
Regulatory Matters [Line Items]
Loss contingency, damages sought					$ 42,000
Distribution Platform Modernization Plan
Regulatory Matters [Line Items]
Approved amount of annual increase (decrease)				$ 516,000
Period of grid modernization plan				3 years
Decoupling Rider | The Ohio Companies
Regulatory Matters [Line Items]
Amount of refunds announced							$ 27,000
Rider CSR | The Ohio Companies
Regulatory Matters [Line Items]
Pre-tax impairment of regulatory asset										$ 108,000
Impairment of regulatory asset, net										84,000
Lost distribution revenue										$ 77,000
Rider DCR | The Ohio Companies
Regulatory Matters [Line Items]
Approved amount of annual increase (decrease)		$ (3,700)
Rider DCR Audit Report | The Ohio Companies
Regulatory Matters [Line Items]
Amount of refunds announced	$ 6,600
Refund to customer of pole attachment sates									$ 15
Number of requirements with minor non-compliance | requirement								8
Number of requirements | requirement								23