Financing - Bank Credit Agreements Narrative (Details) - USD ($) $ in Millions	1 Months Ended
	Jul. 30, 2025	Mar. 31, 2025	Jun. 30, 2025	Feb. 28, 2025
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 8,920
2030			7,600
2027			625
Variable rate pollution control revenue bonds outstanding			1,500
Southern Company, Southern Power, And Mississippi Power
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 3,250		$ 2,450
2030			3,250
Southern Company parent
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			3,000
2030			2,500
2027			500	150
SOUTHERN POWER CO
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			600
2030			600
2027			0
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			275
2030			150
2027			125
Decrease of line of credit		150
Variable rate pollution control revenue bonds outstanding			69
MISSISSIPPI POWER CO | Subsequent Event
Debt Instrument [Line Items]
Repayment of revenue bonds	$ 11
GEORGIA POWER CO
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			2,050
2030			2,050	$ 1,750
2027			0
Decrease of line of credit		300
Variable rate pollution control revenue bonds outstanding			667
Fixed rate pollution control revenue bonds outstanding			501
SOUTHERN Co GAS
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			1,600
2030			1,600
2027			0
Nicor Gas
Debt Instrument [Line Items]
2030		800	800
Decrease of line of credit		$ 100
ALABAMA POWER CO
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			1,365
2030			700
2027			0
Variable rate pollution control revenue bonds outstanding			796
Fixed rate pollution control revenue bonds outstanding			$ 280