RATE MATTERS - KPCo Rate Matters (Details) $ in Millions	1 Months Ended
	Apr. 30, 2026 USD ($)	Feb. 28, 2026 USD ($)	Jan. 31, 2026 USD ($)	Aug. 31, 2025 USD ($)	Mar. 31, 2026 MW	Dec. 31, 2025 USD ($)	Jun. 30, 2025 USD ($)	Jul. 31, 2021
Transource Energy | 2025 Kentucky Base Rate Case
Public Utilities, General Disclosures [Line Items]
Requested annual base rate increase (decrease)			$ 59	$ 96
Requested return on equity			9.80%	10.00%
Requested debt capital structure			53.90%	53.90%
Requested equity capital structure			46.10%	46.10%
Increase in PJM transmission costs				$ 10
Increase due to load loss				9
Requested rate increase related to depreciation rates				6
Annual increase in Kentucky retail rates			$ 77
Requested retail rate increase (decrease), amount			$ 18
Approved return on equity		9.75%	9.70%
Settlement revenue requirement rate decrease year one			$ 25
Settlement revenue requirement rate decrease year two			15
Requested deferred costs, maximum, year one			45
Requested deferred costs, maximum, year two			$ 52
Approved retail rate increase, amount		$ 55
Approved annual base rate increase		36
Increase in new generation rider		19
Annual revenue increase (decrease), amount		22
Reduction related to FERC transmission expense		10
Reduction in incentive and other compensation		$ 9
Regulatory asset, recovery period		30 years
Transource Energy | 2025 Kentucky Base Rate Case | January 2018 through May 2025
Public Utilities, General Disclosures [Line Items]
Previously incurred and capitalized costs required to be reclassified as a regulatory asset		$ 47
Transource Energy | 2025 Kentucky Base Rate Case | Subsequent Event | June 2025 through February 2026
Public Utilities, General Disclosures [Line Items]
Previously incurred and capitalized costs required to be reclassified as a regulatory asset	$ 17
SWEPCo | Mitchell Plant ELG investments
Public Utilities, General Disclosures [Line Items]
Ownership percentage selling								100.00%
Mitchell Plant
Public Utilities, General Disclosures [Line Items]
Jointly owned utility plant, plant capacity | MW					1,560
Mitchell Plant | Transource Energy
Public Utilities, General Disclosures [Line Items]
Jointly owned utility plant, percentage of ownership share					50.00%
Proportionate energy and capacity share							50.00%
Jointly owned utility plant, gross ownership amount of plant in service						$ 517
Requested annual base rate increase (decrease)				$ 20
Mitchell Plant | SWEPCo
Public Utilities, General Disclosures [Line Items]
Jointly owned utility plant, percentage of ownership share					50.00%
Mitchell Plant ELG investments | Transource Energy
Public Utilities, General Disclosures [Line Items]
Jointly owned utility plant, percentage of ownership share								50.00%
Estimated cost to be recovered							$ 78
Mitchell Plant ELG investments | SWEPCo
Public Utilities, General Disclosures [Line Items]
Proportionate ownership share requested to be transferred							50.00%
Mitchell Plant Non-ELG Capital Investments | Transource Energy
Public Utilities, General Disclosures [Line Items]
Estimated cost to be recovered							$ 60
Mitchell Plant Non-ELG Capital Investments | SWEPCo
Public Utilities, General Disclosures [Line Items]
Jointly owned utility plant, percentage of ownership share								50.00%
Proportionate ownership share requested to be transferred							50.00%