Regulatory Matters - GAS Nicor Gas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Total operating revenues	$ (5,748)	$ (7,206)	$ (12,228)	$ (13,854)
Total operating expenses	4,458	$ 5,551	$ 9,719	$ 10,815
Nicor Gas
Public Utilities, General Disclosures [Line Items]
Pre-tax charge to income	38
After-tax charge to income	28
Nicor Gas | Investing in Illinois
Public Utilities, General Disclosures [Line Items]
Capital expenditures disallowed					$ 32
Capital expenditures					$ 415
Total operating revenues	8
Total operating expenses	$ 30