Retirement Benefits (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year	$ 0		$ 0
Pension Plans and Postretirement Plans
Service cost	69,000,000	$ 103,000,000	138,000,000	$ 206,000,000
Interest cost	157,000,000	102,000,000	313,000,000	204,000,000
Expected return on plan assets	(308,000,000)	(317,000,000)	(615,000,000)	(633,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	8,000,000	60,000,000	16,000,000	120,000,000
Net periodic pension income	(74,000,000)	(52,000,000)	(148,000,000)	(103,000,000)
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	16,000,000	24,000,000	32,000,000	49,000,000
Interest cost	36,000,000	24,000,000	72,000,000	48,000,000
Expected return on plan assets	(74,000,000)	(75,000,000)	(148,000,000)	(152,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	3,000,000	15,000,000	5,000,000	31,000,000
Net periodic pension income	(19,000,000)	(12,000,000)	(39,000,000)	(24,000,000)
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	17,000,000	26,000,000	34,000,000	52,000,000
Interest cost	47,000,000	30,000,000	95,000,000	61,000,000
Expected return on plan assets	(96,000,000)	(100,000,000)	(192,000,000)	(199,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain) loss	3,000,000	19,000,000	6,000,000	37,000,000
Net periodic pension income	(28,000,000)	(24,000,000)	(56,000,000)	(48,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	4,000,000	6,000,000	8,000,000
Interest cost	7,000,000	4,000,000	14,000,000	9,000,000
Expected return on plan assets	(14,000,000)	(14,000,000)	(28,000,000)	(29,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	4,000,000	0	7,000,000
Net periodic pension income	(4,000,000)	(2,000,000)	(8,000,000)	(5,000,000)
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	3,000,000	3,000,000	5,000,000
Interest cost	2,000,000	1,000,000	4,000,000	3,000,000
Expected return on plan assets	(4,000,000)	(4,000,000)	(8,000,000)	(8,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	0	1,000,000
Net periodic pension income	(1,000,000)	0	(1,000,000)	1,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	6,000,000	8,000,000	12,000,000	17,000,000
Interest cost	11,000,000	7,000,000	21,000,000	14,000,000
Expected return on plan assets	(22,000,000)	(24,000,000)	(44,000,000)	(46,000,000)
Amortization:
Prior service costs	(1,000,000)	0	(1,000,000)	(1,000,000)
Regulatory asset	4,000,000	4,000,000	8,000,000	8,000,000
Net (gain) loss	(1,000,000)	1,000,000	(2,000,000)	3,000,000
Net periodic pension income	(3,000,000)	(4,000,000)	(6,000,000)	(5,000,000)
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	3,000,000	5,000,000	7,000,000	11,000,000
Interest cost	17,000,000	11,000,000	35,000,000	21,000,000
Expected return on plan assets	(20,000,000)	(20,000,000)	(41,000,000)	(40,000,000)
Amortization:
Prior service costs	1,000,000		1,000,000
Regulatory asset	0	0	0	0
Net (gain) loss	(3,000,000)	0	(6,000,000)	0
Net periodic pension income	(2,000,000)	(4,000,000)	(4,000,000)	(8,000,000)
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	2,000,000	2,000,000	3,000,000
Interest cost	4,000,000	2,000,000	8,000,000	5,000,000
Expected return on plan assets	(9,000,000)	(8,000,000)	(17,000,000)	(16,000,000)
Amortization:
Prior service costs	0		0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	(1,000,000)	0
Net periodic pension income	(4,000,000)	(4,000,000)	(8,000,000)	(8,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	2,000,000	3,000,000
Interest cost	7,000,000	3,000,000	13,000,000	7,000,000
Expected return on plan assets	(8,000,000)	(6,000,000)	(15,000,000)	(13,000,000)
Amortization:
Prior service costs	0		0
Regulatory asset	0	0	0	0
Net (gain) loss	(1,000,000)	1,000,000	(2,000,000)	1,000,000
Net periodic pension income	(1,000,000)	(1,000,000)	(2,000,000)	(2,000,000)
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0	0	0
Interest cost	1,000,000	1,000,000	2,000,000	1,000,000
Expected return on plan assets	0	(1,000,000)	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0		0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	0	0
Net periodic pension income	1,000,000	0	1,000,000	0
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0	0	0
Interest cost	0	0	0	0
Expected return on plan assets	0	0	0	0
Amortization:
Prior service costs	0		0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	0	0
Net periodic pension income	0	0	0	0
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	0	0	1,000,000
Interest cost	2,000,000	1,000,000	4,000,000	2,000,000
Expected return on plan assets	(2,000,000)	(1,000,000)	(3,000,000)	(3,000,000)
Amortization:
Prior service costs	0		0
Regulatory asset	2,000,000	1,000,000	3,000,000	3,000,000
Net (gain) loss	(1,000,000)	0	(2,000,000)	(1,000,000)
Net periodic pension income	$ 1,000,000	$ 1,000,000	$ 2,000,000	$ 2,000,000