Regulatory Matters - GAS Schedule of Infrastructure Replacement Programs and Capital Projects (Details) - SOUTHERN Co GAS $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Public Utilities, General Disclosures [Line Items]
Capital expenditures	$ 80
Investing in Illinois
Public Utilities, General Disclosures [Line Items]
Capital expenditures	51
Steps to Advance Virginia's Energy
Public Utilities, General Disclosures [Line Items]
Capital expenditures	14
System Reinforcement Rider
Public Utilities, General Disclosures [Line Items]
Capital expenditures	14
Pipeline Replacement Program
Public Utilities, General Disclosures [Line Items]
Capital expenditures	$ 1