Regulatory Matters - GAS Schedule of Infrastructure Replacement Programs and Capital Projects (Details) - SOUTHERN Co GAS $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($)
Public Utilities, General Disclosures [Line Items]
Capital expenditures	$ 416
Investing in Illinois
Public Utilities, General Disclosures [Line Items]
Capital expenditures	311
SAVE
Public Utilities, General Disclosures [Line Items]
Capital expenditures	52
System Reinforcement Rider
Public Utilities, General Disclosures [Line Items]
Capital expenditures	51
Pipeline Replacement Program
Public Utilities, General Disclosures [Line Items]
Capital expenditures	$ 2