Financing - Schedule of Credit Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Feb. 28, 2025
Line of Credit Facility [Line Items]
2026	$ 695
2027	625
2030	7,600
Total	8,920
Unused	8,892
Expires within One Year	30
Southern Company parent
Line of Credit Facility [Line Items]
2026	0
2027	500		$ 150
2030	2,500
Total	3,000
Unused	2,999
Expires within One Year	0
ALABAMA POWER CO
Line of Credit Facility [Line Items]
2026	665
2027	0
2030	700
Total	1,365
Unused	1,364
Expires within One Year	0
GEORGIA POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	0
2030	2,050		1,750
Total	2,050
Unused	2,026
Expires within One Year	0
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	125
2030	150
Total	275
Unused	275
Expires within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	0
2030	600
Total	600
Unused	600
Expires within One Year	0
SOUTHERN POWER CO | Continuing Letter of Credit Facility A
Line of Credit Facility [Line Items]
2026	75
Unused	17
SOUTHERN POWER CO | Continuing Letter of Credit Facility B
Line of Credit Facility [Line Items]
2027	100
Unused	4
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
2026	0
2027	0
2030	1,600
Total	1,600
Unused	1,598
Expires within One Year	0
2029			1,500
SEGCO
Line of Credit Facility [Line Items]
2026	30
2027	0
2030	0
Total	30
Unused	30
Expires within One Year	30
Southern Company, Southern Power, And Mississippi Power
Line of Credit Facility [Line Items]
2030	3,250
Total		$ 3,250	$ 2,450
Alabama Property Company
Line of Credit Facility [Line Items]
2026	15
Unused	14
Southern Company Gas Capital
Line of Credit Facility [Line Items]
2030	800	800
Nicor Gas
Line of Credit Facility [Line Items]
2030	$ 800	$ 800