RATE MATTERS - APCo and WPCo Rate Matters (Details) - APCo $ in Millions	1 Months Ended
	Sep. 30, 2025 USD ($)	Aug. 31, 2025 USD ($)	Apr. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Nov. 30, 2024 USD ($) consecutiveYear	Aug. 31, 2024 USD ($)	Apr. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Jan. 31, 2024 USD ($)	Oct. 29, 2025 USD ($)	Jul. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Jan. 31, 2025 USD ($)	Feb. 29, 2024 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	$ 2,527.6
ENEC Under-Recovery Regulatory Assets
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	412.4
Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	1,704.2
Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	236.8
Storm-Related Costs
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	157.9
West Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization				$ 2,400.0
West Virginia | ENEC Under-Recovery Regulatory Assets
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization				321.0
West Virginia | Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization				237.0
West Virginia | Storm-Related Costs
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization				118.0
VIRGINIA
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization											$ 1,400.0
Regulatory asset, requested to be financed through securitization (in years)											20 years
VIRGINIA | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization										$ 1,400.0
VIRGINIA | Storm-Related Costs
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization											$ 141.0
APCo Portion
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	1,565.1
APCo Portion | ENEC Under-Recovery Regulatory Assets
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	166.6
APCo Portion | Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	1,145.5
APCo Portion | Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	87.6
APCo Portion | Storm-Related Costs
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization	$ 155.0
Mitchell & Mountaineer Plants | West Virginia | Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization				1,700.0
Amos and Mountaineer Plants | VIRGINIA
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization (in years)											20 years
Amos and Mountaineer Plants | VIRGINIA | Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Public Utilities, General Disclosures [Line Items]
Regulatory asset, requested to be financed through securitization											$ 1,200.0
Mitchell Plant | KPCo
Public Utilities, General Disclosures [Line Items]
Share of energy and capacity utilized by other party, percentage	50.00%
ENEC Filing
Public Utilities, General Disclosures [Line Items]
Under recovered costs disallowance		$ 232.0		232.0					$ 232.0					$ 232.0
Approved recovery under recovered costs							$ 321.0		$ 321.0
Approved carrying charges							4.00%		4.00%
Approved carrying charges, recovery period							10 years		10 years
Reduction of under-recovered costs disallowance												$ 179.0
Requested annual base rate increase (decrease)			$ 72.0				$ 58.0
Approved annual base rate increase	$ 70.0
Public utilities, denied, under-recovered costs disallowance	$ 19.0
ENEC Filing | Period ending February 29, 2024
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)							20.0
Approved annual base rate increase				$ 20.0
ENEC Filing | Period September 2024 through August 2025
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)							$ 38.0
Approved annual base rate increase						$ 38.0
ENEC Filing | APCo Portion
Public Utilities, General Disclosures [Line Items]
Under recovered costs disallowance									$ 136.0
Approved recovery under recovered costs									$ 174.0
Virginia Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Under recovered costs disallowance			$ 20.0									$ 0.0	$ 20.0
2024 West Virginia Base Rate Case
Public Utilities, General Disclosures [Line Items]
Approved recovery under recovered costs		24.0			$ 118.0
Requested annual base rate increase (decrease)					$ 251.0
Approved annual base rate increase		$ 76.0
Requested return on equity					10.80%
Requested debt capital structure					52.00%
Requested equity capital structure					48.00%
Requested recovery, under-recovered costs, period					3 years
Regulatory assets expected to be recovered through securitization					$ 2,400.0
Requested annual increase without securitization					$ 37.0
Annual increase april 1st surcharge		3.00%			3.00%
Annual increase, surcharges, number of consecutive years | consecutiveYear					4
Annual increase april 1st surcharge, proposed filing period					4 years
Approved return on equity		9.25%
Approved capital structure, percentage		56.00%
Approved equity capital structure, percentage		44.00%
2024 West Virginia Base Rate Case | APCo Portion
Public Utilities, General Disclosures [Line Items]
Approved annual base rate increase		$ 67.0
Modified Rate Base Cost
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)					$ 94.0
Mitchell Base Rate Surcharge
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)					$ 21.0
West Virginia Modified Rate Base Cost
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)								$ 32.0