Rate Matters East Companies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Other Asset Impairment Charges	$ 0.0	$ 156.4	$ 70.6
Total Property, Plant and Equipment, Net	63,901.6	60,138.1
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Other Asset Impairment Charges	0.0	92.9	$ 0.0
Total Property, Plant and Equipment, Net	11,394.1	11,081.9
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	7,052.3	6,899.7
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	$ 7,452.1	6,907.0
2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Percent of Excess Earnings Subject to Refund	70.00%
Basis Points Over Authorized Return on Equity Considered Excess Earnings	70.00%
Approved Return on Common Equity for Prior Period	9.42%
Requested Annual Increase	$ 65.0
Requested Return on Equity	9.90%
Amount Of Increased Depreciation Expense Requested	$ 19.0
Amount of Increase Related to Calculated Shortfall	$ 8.0
Total Basis Point Band for Authorized Return on Equity	140.00%
Approved Return on Common Equity	9.20%
Net Increase in Pretax Income Due to Virginia SCC Order	$ 40.0
Pretax Income Reduction Related to 2018 and 2019 Depreciation Studies	47.0
Reduction to revenues for amounts recognized in advance of the recording of depreciation expense for the periods January 2018 through October 2020	44.0
Increase in Depreciation Expense for the Periods November and December 2020	3.0
Corresponding Regulatory Liability that was Recorded for Reduction to Revenues	44.0
West Virginia ENEC and Vegetation Management Riders [Member]
Public Utilities, General Disclosures [Line Items]
Increase in Rider Rates related to Expanded Net Energy Cost and Vegetation Management	101.0
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	38.0
West Virginia ENEC and Vegetation Management Riders [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Increase in Rider Rates related to Expanded Net Energy Cost and Vegetation Management	81.0
Refund for Excess ADIT Not Subject to Rate Normalization Requirements	31.0
2019 Indiana Base Rate Case [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 172.0
Requested Return on Equity	10.50%
Approved Return on Common Equity	9.70%
Amount of Increase Related to Annual Depreciation Rates	$ 78.0
Amount of Increase Related to Annual Depreciation Rates due to Proposed Investments	52.0
Amount of Increase Related to Annual Depreciation Rates due to Increased Depreciation Expense	26.0
Approved Annual Revenue Increase	60.0
Initial Phased in Annual Increase	44.0
Impact on Pretax Earnings due to Loss of Significant Contract	20.0
2020 Kentucky Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 65.0
Requested Return on Equity	10.00%
Approved Return on Common Equity	9.30%
Approved Annual Revenue Increase	$ 53.0
Requested Recovery Amount of Previously Authorized Deferral	50.0
Approved Annual Revenue Increase Prior to Rehearing	52.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 42.0
Requested Return on Equity	10.15%
Staff Recommended Annual Revenue Cap for the DIR in 2021	$ 57.0
Staff Recommended Annual Revenue Cap for the DIR in 2022	78.0
Staff Recommended Annual Revenue Cap for the DIR in 2023	96.0
Staff Recommended Annual Revenue Cap for the DIR for the First Five Months of 2024	46.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Demand Side Management Programs [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	40.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Employee Related Expense [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	23.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Rate Base [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	19.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Property Tax [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	17.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Other Various Expenses [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	15.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Depreciation Expense [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	11.0
2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Vegetation Management Programs [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	10.0
2019 Ohio DIR Audit [Member]
Public Utilities, General Disclosures [Line Items]
DIR Revenue Amount above 2019 Authorized Limit	$ 17.0
Minimum [Member] | 2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return on Common Equity	8.50%
Minimum [Member] | 2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Annual Rate Decrease	$ 102.0
Staff Recommended Return on Common Equity	8.76%
Minimum [Member] | 2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Return on Common Equity [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	$ 9.0
Maximum [Member] | 2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return on Common Equity	9.90%
Maximum [Member] | 2019 Indiana Base Rate Case [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Approved Annual Revenue Increase	$ 77.0
Maximum [Member] | 2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Annual Rate Decrease	$ 123.0
Staff Recommended Return on Common Equity	9.78%
Maximum [Member] | 2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member] | Return on Common Equity [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Adjustments to Companies Request	$ 30.0
Plant in Service [Member] | Maximum [Member] | 2020 Ohio Base Rate Case [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance from Staff or Intervenors	27.0
Plant Retirement Costs - Unrecovered Plant [Member] | 2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Net Book Value of Retired Plants	93.0
Other Asset Impairment Charges	93.0
Virginia Jurisdictional AMR Meters [Member] | 2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	35.0	51.0
Virginia Jurisdictional AMI Meters [Member] | 2017-2019 Virginia Triennial Review [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	$ 73.0	$ 75.0