REGULATORY MATTERS - GAS (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Nov. 16, 2023	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Revenues				$ (25,253.0)	$ (29,279.0)	$ (23,113.0)
Total operating expenses				19,427.0	$ 23,909.0	$ 19,415.0
Nicor Gas
Public Utilities, General Disclosures [Line Items]
Infrastructure disallowed		$ 69.0
Pretax charge to income		58.0	$ 38.0	(96.0)
After tax charge to income		$ 44.0	28.0	(72.0)
Investing In Illinois Qualifying Infrastructure Plant | Nicor Gas
Public Utilities, General Disclosures [Line Items]
Infrastructure disallowed	$ 126.8			$ 63.0			$ 32.0
Capital expenditures							$ 415.0
Revenues			8.0
Total operating expenses			$ 30.0
QIP Rider | Nicor Gas
Public Utilities, General Disclosures [Line Items]
Infrastructure disallowed	$ 31.0