REGULATORY ENVIRONMENT - PGL QIP RIDER (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) Assurance	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Assurance	Sep. 30, 2023 USD ($)	Aug. 14, 2024 USD ($)
Public Utilities, General Disclosures [Line Items]
Pre-tax charge to income	$ (270.2)	$ (376.0)	$ (1,232.1)	$ (1,296.2)
Reduction in revenues	(1,863.5)	(1,957.4)	(6,315.7)	(6,675.5)
Operation and maintenance expense	566.8	516.6	1,631.0	1,546.6
Interest expense	204.2	$ 182.5	596.8	$ 533.4
Illinois Commerce Commission (ICC) | PGL | 2016 Annual QIP Rider Reconciliation
Public Utilities, General Disclosures [Line Items]
Disallowed capital costs					$ 14.8
Pre-tax charge to income	25.3
Reduction in revenues	12.9
Operation and maintenance expense	12.1
Interest expense	0.3
Illinois Commerce Commission (ICC) | PGL | QIP Rider Open Reconciliations 2017-2023
Public Utilities, General Disclosures [Line Items]
Aggregate capital costs during open reconciliation years	$ 2,058.0		$ 2,058.0
Amount of assurance that QIP rider costs will be recoverable | Assurance	0		0