Retirement Benefits (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year	$ 0
Pension Plans and Postretirement Plans
Service cost	69,000,000	$ 103,000,000
Interest cost	156,000,000	102,000,000
Expected return on plan assets	(307,000,000)	(316,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net gain	8,000,000	60,000,000
Net periodic pension cost (income)	(74,000,000)	(51,000,000)
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	16,000,000	25,000,000
Interest cost	36,000,000	24,000,000
Expected return on plan assets	(74,000,000)	(77,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net gain	2,000,000	16,000,000
Net periodic pension cost (income)	(20,000,000)	(12,000,000)
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	17,000,000	26,000,000
Interest cost	48,000,000	31,000,000
Expected return on plan assets	(96,000,000)	(99,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net gain	3,000,000	18,000,000
Net periodic pension cost (income)	(28,000,000)	(24,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	4,000,000
Interest cost	7,000,000	5,000,000
Expected return on plan assets	(14,000,000)	(15,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net gain	0	3,000,000
Net periodic pension cost (income)	(4,000,000)	(3,000,000)
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000
Interest cost	2,000,000	2,000,000
Expected return on plan assets	(4,000,000)	(4,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net gain	0	1,000,000
Net periodic pension cost (income)	0	1,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	6,000,000	9,000,000
Interest cost	11,000,000	7,000,000
Expected return on plan assets	(22,000,000)	(22,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)
Regulatory asset	4,000,000	4,000,000
Net gain	(1,000,000)	2,000,000
Net periodic pension cost (income)	(3,000,000)	(1,000,000)
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	4,000,000	6,000,000
Interest cost	18,000,000	10,000,000
Expected return on plan assets	(21,000,000)	(20,000,000)
Amortization:
Regulatory asset	0	0
Net gain	(3,000,000)
Net periodic pension cost (income)	(2,000,000)	(4,000,000)
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000
Interest cost	4,000,000	3,000,000
Expected return on plan assets	(8,000,000)	(8,000,000)
Amortization:
Regulatory asset	0	0
Net gain	(1,000,000)
Net periodic pension cost (income)	(4,000,000)	(4,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	2,000,000
Interest cost	6,000,000	4,000,000
Expected return on plan assets	(7,000,000)	(7,000,000)
Amortization:
Regulatory asset	0	0
Net gain	(1,000,000)
Net periodic pension cost (income)	(1,000,000)	(1,000,000)
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	1,000,000	0
Expected return on plan assets	(1,000,000)	0
Amortization:
Regulatory asset	0	0
Net gain	0
Net periodic pension cost (income)	0	0
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	0	0
Expected return on plan assets	0	0
Amortization:
Regulatory asset	0	0
Net gain	0
Net periodic pension cost (income)	0	0
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	2,000,000	1,000,000
Expected return on plan assets	(2,000,000)	(2,000,000)
Amortization:
Regulatory asset	2,000,000	2,000,000
Net gain	(1,000,000)
Net periodic pension cost (income)	$ 1,000,000	$ 1,000,000