Financing - Schedule of Credit Arrangements (Details) $ in Millions	Mar. 31, 2024 USD ($)
Line of Credit Facility [Line Items]
Expires, 2024	$ 280
Expires, 2026	800
Expires, 2027	125
Expires, 2028	6,400
Total	7,605
Unused	7,577
Expires within One Year	280
Southern Company parent
Line of Credit Facility [Line Items]
Expires, 2024	150
Expires, 2026	0
Expires, 2027	0
Expires, 2028	1,850
Total	2,000
Unused	1,998
Expires within One Year	150
ALABAMA POWER CO
Line of Credit Facility [Line Items]
Expires, 2024	0
Expires, 2026	650
Expires, 2027	0
Expires, 2028	700
Total	1,350
Unused	1,350
Expires within One Year	0
GEORGIA POWER CO
Line of Credit Facility [Line Items]
Expires, 2024	0
Expires, 2026	0
Expires, 2027	0
Expires, 2028	1,750
Total	1,750
Unused	1,726
Expires within One Year	0
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
Expires, 2024	0
Expires, 2026	150
Expires, 2027	125
Expires, 2028	0
Total	275
Unused	275
Expires within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
Expires, 2024	0
Expires, 2026	0
Expires, 2027	0
Expires, 2028	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]
Expires, 2026	100
Unused	8
Expires, 2025	75
SOUTHERN POWER CO | Continuing Letter of Credit Facility B
Line of Credit Facility [Line Items]
Unused	7
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
Expires, 2024	100
Expires, 2026	0
Expires, 2027	0
Expires, 2028	1,500
Total	1,600
Unused	1,598
Expires within One Year	100
SEGCO
Line of Credit Facility [Line Items]
Expires, 2024	30
Expires, 2026	0
Expires, 2027	0
Expires, 2028	0
Total	30
Unused	30
Expires within One Year	30
Southern Company and Southern Power
Line of Credit Facility [Line Items]
Expires, 2028	2,450
Southern Company Gas Capital
Line of Credit Facility [Line Items]
Expires, 2028	800
Nicor Gas
Line of Credit Facility [Line Items]
Expires, 2024	100
Expires, 2028	$ 700