Retirement Benefits (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2025
Pension Plans
Pension Plans and Postretirement Plans
Service cost	$ 66,000,000	$ 73,000,000	$ 132,000,000	$ 146,000,000
Interest cost	166,000,000	158,000,000	332,000,000	317,000,000
Expected return on plan assets	(320,000,000)	(315,000,000)	(640,000,000)	(631,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	10,000,000	13,000,000	19,000,000	27,000,000
Net periodic pension income	(78,000,000)	(71,000,000)	(157,000,000)	(141,000,000)
Pension Plans | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year					$ 0
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	15,000,000	17,000,000	30,000,000	34,000,000
Interest cost	38,000,000	37,000,000	77,000,000	74,000,000
Expected return on plan assets	(78,000,000)	(76,000,000)	(156,000,000)	(153,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	4,000,000	4,000,000	6,000,000	8,000,000
Net periodic pension income	(21,000,000)	(18,000,000)	(43,000,000)	(37,000,000)
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	15,000,000	17,000,000	31,000,000	35,000,000
Interest cost	49,000,000	48,000,000	98,000,000	96,000,000
Expected return on plan assets	(99,000,000)	(98,000,000)	(198,000,000)	(197,000,000)
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	4,000,000	7,000,000	9,000,000
Net periodic pension income	(31,000,000)	(28,000,000)	(61,000,000)	(56,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	3,000,000	5,000,000	6,000,000
Interest cost	8,000,000	7,000,000	15,000,000	14,000,000
Expected return on plan assets	(14,000,000)	(15,000,000)	(29,000,000)	(29,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	2,000,000	1,000,000	2,000,000
Net periodic pension income	(4,000,000)	(3,000,000)	(8,000,000)	(7,000,000)
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	1,000,000	3,000,000	3,000,000
Interest cost	3,000,000	2,000,000	5,000,000	4,000,000
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	(2,000,000)	1,000,000	(1,000,000)	1,000,000
Net periodic pension income	(1,000,000)	0	(1,000,000)	0
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	7,000,000	7,000,000	13,000,000	14,000,000
Interest cost	11,000,000	11,000,000	22,000,000	21,000,000
Expected return on plan assets	(22,000,000)	(21,000,000)	(43,000,000)	(43,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Regulatory asset	4,000,000	4,000,000	8,000,000	8,000,000
Net (gain) loss	0	0	0	0
Net periodic pension income	(1,000,000)	0	(1,000,000)	(1,000,000)
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	3,000,000	3,000,000	6,000,000	7,000,000
Interest cost	18,000,000	17,000,000	35,000,000	33,000,000
Expected return on plan assets	(22,000,000)	(22,000,000)	(45,000,000)	(44,000,000)
Amortization:
Prior service costs			1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain) loss	(4,000,000)	(4,000,000)	(7,000,000)	(8,000,000)
Net periodic pension income	(5,000,000)	(6,000,000)	(10,000,000)	(11,000,000)
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	2,000,000	2,000,000
Interest cost	4,000,000	4,000,000	8,000,000	8,000,000
Expected return on plan assets	(9,000,000)	(8,000,000)	(18,000,000)	(17,000,000)
Amortization:
Prior service costs			0	0
Regulatory asset	0	0	0	0
Net (gain) loss	0	(2,000,000)	0	(2,000,000)
Net periodic pension income	(4,000,000)	(5,000,000)	(8,000,000)	(9,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	2,000,000	2,000,000
Interest cost	7,000,000	5,000,000	13,000,000	11,000,000
Expected return on plan assets	(8,000,000)	(8,000,000)	(16,000,000)	(16,000,000)
Amortization:
Prior service costs			0	0
Regulatory asset	0	0	0	0
Net (gain) loss	(2,000,000)	0	(2,000,000)	(1,000,000)
Net periodic pension income	(2,000,000)	(2,000,000)	(3,000,000)	(4,000,000)
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0	0	0
Interest cost	0	0	1,000,000	1,000,000
Expected return on plan assets	0	0	0	0
Amortization:
Prior service costs			0	0
Regulatory asset	0	0	0	0
Net (gain) loss	1,000,000	0	0	(1,000,000)
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	0
Interest cost	2,000,000	2,000,000	4,000,000	4,000,000
Expected return on plan assets	(2,000,000)	(2,000,000)	(4,000,000)	(4,000,000)
Amortization:
Prior service costs			0	0
Regulatory asset	2,000,000	2,000,000	3,000,000	3,000,000
Net (gain) loss	(2,000,000)	(1,000,000)	(4,000,000)	(3,000,000)
Net periodic pension income	$ 0	$ 1,000,000	$ (1,000,000)	$ 0