RATE MATTERS - Regulatory Assets Subject to Securitization (Details) - APCo $ in Millions	Jun. 30, 2025 USD ($)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	$ 2,395.8
Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	1,704.2
ENEC Under-Recovery Regulatory Assets (as of February 28, 2023)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	321.1
Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	236.8
Storm-Related Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	117.9
Upfront Financing Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	15.8
APCo Portion
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	1,532.5
APCo Portion \| Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	1,145.5
APCo Portion \| ENEC Under-Recovery Regulatory Assets (as of February 28, 2023)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	174.3
APCo Portion \| Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	87.6
APCo Portion \| Storm-Related Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	115.0
APCo Portion \| Upfront Financing Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	10.1
WPCo Portion
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	863.3
WPCo Portion \| Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	558.7
WPCo Portion \| ENEC Under-Recovery Regulatory Assets (as of February 28, 2023)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	146.8
WPCo Portion \| Forecasted Undepreciated CCR and ELG Investments of Amos, Mitchell and Mountaineer (as of November 30, 2024)
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	149.2
WPCo Portion \| Storm-Related Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	2.9
WPCo Portion \| Upfront Financing Costs
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	$ 5.7

RATE MATTERS - Regulatory Assets Subject to Securitization (Details) - APCo
$ in Millions

Jun. 30, 2025

USD ($)

Regulatory Asset [Line Items]

Regulatory asset, requested to be financed through securitization

$ 2,395.8

Undepreciated Utility Plant Balances of Amos, Mitchell and Mountaineer (as of December 31, 2022)

Regulatory Asset [Line Items]

Regulatory asset, requested to be financed through securitization

1,704.2

ENEC Under-Recovery Regulatory Assets (as of February 28, 2023)

Regulatory Asset [Line Items]