Retirement Benefits (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 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	207,000,000	$ 309,000,000
Interest cost	156,000,000	102,000,000	469,000,000	306,000,000
Expected return on plan assets	(307,000,000)	(316,000,000)	(922,000,000)	(949,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	8,000,000	60,000,000	24,000,000	180,000,000
Net periodic pension income	(74,000,000)	(51,000,000)	(222,000,000)	(154,000,000)
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	16,000,000	25,000,000	48,000,000	74,000,000
Interest cost	37,000,000	24,000,000	109,000,000	72,000,000
Expected return on plan assets	(75,000,000)	(77,000,000)	(223,000,000)	(229,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	2,000,000	16,000,000	7,000,000	47,000,000
Net periodic pension income	(20,000,000)	(12,000,000)	(59,000,000)	(36,000,000)
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	17,000,000	26,000,000	51,000,000	78,000,000
Interest cost	48,000,000	31,000,000	143,000,000	92,000,000
Expected return on plan assets	(97,000,000)	(99,000,000)	(289,000,000)	(298,000,000)
Amortization:
Prior service costs	0	0	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain) loss	4,000,000	18,000,000	10,000,000	55,000,000
Net periodic pension income	(28,000,000)	(24,000,000)	(84,000,000)	(72,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	5,000,000	8,000,000	13,000,000
Interest cost	7,000,000	5,000,000	21,000,000	14,000,000
Expected return on plan assets	(13,000,000)	(15,000,000)	(41,000,000)	(44,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	1,000,000	2,000,000	1,000,000	9,000,000
Net periodic pension income	(3,000,000)	(3,000,000)	(11,000,000)	(8,000,000)
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	5,000,000	7,000,000
Interest cost	2,000,000	2,000,000	6,000,000	5,000,000
Expected return on plan assets	(4,000,000)	(4,000,000)	(12,000,000)	(12,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	1,000,000	0	2,000,000
Net periodic pension income	0	1,000,000	(1,000,000)	2,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	6,000,000	9,000,000	18,000,000	26,000,000
Interest cost	11,000,000	7,000,000	32,000,000	21,000,000
Expected return on plan assets	(22,000,000)	(22,000,000)	(65,000,000)	(68,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)	(2,000,000)	(2,000,000)
Regulatory asset	4,000,000	3,000,000	11,000,000	11,000,000
Net (gain) loss	(1,000,000)	2,000,000	(3,000,000)	5,000,000
Net periodic pension income	(3,000,000)	(2,000,000)	(9,000,000)	(7,000,000)
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	4,000,000	6,000,000	11,000,000	17,000,000
Interest cost	18,000,000	10,000,000	53,000,000	31,000,000
Expected return on plan assets	(21,000,000)	(20,000,000)	(62,000,000)	(60,000,000)
Amortization:
Prior service costs	0	(1,000,000)	1,000,000	(1,000,000)
Regulatory asset	0	0	0	0
Net (gain) loss	(4,000,000)	1,000,000	(10,000,000)	1,000,000
Net periodic pension income	(3,000,000)	(4,000,000)	(7,000,000)	(12,000,000)
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	2,000,000	3,000,000	5,000,000
Interest cost	5,000,000	3,000,000	13,000,000	8,000,000
Expected return on plan assets	(9,000,000)	(9,000,000)	(26,000,000)	(25,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	(1,000,000)	0	(2,000,000)	0
Net periodic pension income	(4,000,000)	(4,000,000)	(12,000,000)	(12,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	2,000,000	3,000,000	5,000,000
Interest cost	6,000,000	4,000,000	19,000,000	11,000,000
Expected return on plan assets	(7,000,000)	(8,000,000)	(22,000,000)	(21,000,000)
Amortization:
Prior service costs	1,000,000	0	1,000,000	0
Regulatory asset	0	0	0	0
Net (gain) loss	(1,000,000)	0	(3,000,000)	1,000,000
Net periodic pension income	0	(2,000,000)	(2,000,000)	(4,000,000)
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	1,000,000	0	1,000,000
Interest cost	1,000,000	0	2,000,000	1,000,000
Expected return on plan assets	(1,000,000)	0	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	0	0
Net periodic pension income	0	1,000,000	1,000,000	1,000,000
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	0	1,000,000	0	1,000,000
Interest cost	0	0	0	0
Expected return on plan assets	0	0	0	0
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	0	0	0
Net periodic pension income	0	1,000,000	0	1,000,000
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	0	1,000,000	1,000,000
Interest cost	2,000,000	1,000,000	6,000,000	4,000,000
Expected return on plan assets	(2,000,000)	(2,000,000)	(5,000,000)	(6,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	2,000,000	2,000,000	5,000,000	5,000,000
Net (gain) loss	(1,000,000)	(1,000,000)	(3,000,000)	(2,000,000)
Net periodic pension income	$ 1,000,000	$ 0	$ 4,000,000	$ 2,000,000