REGULATORY MATTERS - GAS Capital Projects Schedule of QIP (Details) - Nicor Gas - USD ($) $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 24, 2024	Nov. 30, 2023	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2019
Commitments [Line Items]
Disallowed			$ 69.0
Investing In Illinois Qualifying Infrastructure Plant
Commitments [Line Items]
Capital Investments				$ 3,228.0
Disallowed	$ 14.0	$ 126.8		63.0	$ 32.0
Investing In Illinois Qualifying Infrastructure Plant \| Complete
Commitments [Line Items]
Capital Investments				1,246.0
Disallowed				0.0
Investing In Illinois Qualifying Infrastructure Plant \| Complete, Appealed
Commitments [Line Items]
Capital Investments				415.0
Disallowed				32.0
Investing In Illinois Qualifying Infrastructure Plant \| Filed March 2021
Commitments [Line Items]
Capital Investments				402.0
Investing In Illinois Qualifying Infrastructure Plant \| Filed March 2022
Commitments [Line Items]
Capital Investments				392.0
Investing In Illinois Qualifying Infrastructure Plant \| Filed March 2023
Commitments [Line Items]
Capital Investments				408.0
Disallowed				6.0
Investing In Illinois Qualifying Infrastructure Plant \| Filed March 2024
Commitments [Line Items]
Capital Investments				365.0
Disallowed				$ 25.0