Retirement Benefits (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
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	103,000,000	$ 108,000,000	206,000,000	$ 217,000,000
Interest cost	102,000,000	86,000,000	204,000,000	173,000,000
Expected return on plan assets	(317,000,000)	(297,000,000)	(633,000,000)	(595,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net loss	60,000,000	79,000,000	120,000,000	157,000,000
Net periodic pension cost (income)	(52,000,000)	(24,000,000)	(103,000,000)	(48,000,000)
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	24,000,000	25,000,000	49,000,000	51,000,000
Interest cost	24,000,000	21,000,000	48,000,000	41,000,000
Expected return on plan assets	(75,000,000)	(71,000,000)	(152,000,000)	(143,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net loss	15,000,000	20,000,000	31,000,000	41,000,000
Net periodic pension cost (income)	(12,000,000)	(5,000,000)	(24,000,000)	(10,000,000)
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	26,000,000	28,000,000	52,000,000	56,000,000
Interest cost	30,000,000	26,000,000	61,000,000	52,000,000
Expected return on plan assets	(100,000,000)	(94,000,000)	(199,000,000)	(188,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net loss	19,000,000	25,000,000	37,000,000	50,000,000
Net periodic pension cost (income)	(24,000,000)	(14,000,000)	(48,000,000)	(29,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	4,000,000	5,000,000	8,000,000	9,000,000
Interest cost	4,000,000	4,000,000	9,000,000	8,000,000
Expected return on plan assets	(14,000,000)	(13,000,000)	(29,000,000)	(27,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net loss	4,000,000	3,000,000	7,000,000	7,000,000
Net periodic pension cost (income)	(2,000,000)	(1,000,000)	(5,000,000)	(3,000,000)
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	3,000,000	5,000,000	5,000,000
Interest cost	1,000,000	1,000,000	3,000,000	2,000,000
Expected return on plan assets	(4,000,000)	(4,000,000)	(8,000,000)	(7,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net loss	0	1,000,000	1,000,000	2,000,000
Net periodic pension cost (income)	0	1,000,000	1,000,000	2,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	8,000,000	9,000,000	17,000,000	18,000,000
Interest cost	7,000,000	6,000,000	14,000,000	12,000,000
Expected return on plan assets	(24,000,000)	(22,000,000)	(46,000,000)	(43,000,000)
Amortization:
Prior service costs	0	0	(1,000,000)	(1,000,000)
Regulatory asset	4,000,000	4,000,000	8,000,000	8,000,000
Net loss	1,000,000	3,000,000	3,000,000	6,000,000
Net periodic pension cost (income)	(4,000,000)	0	(5,000,000)	0
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	5,000,000	6,000,000	11,000,000	12,000,000
Interest cost	11,000,000	9,000,000	21,000,000	17,000,000
Expected return on plan assets	(20,000,000)	(19,000,000)	(40,000,000)	(38,000,000)
Amortization:
Prior service costs		(1,000,000)		(1,000,000)
Regulatory asset	0	0	0	0
Net loss	0	1,000,000	0	2,000,000
Net periodic pension cost (income)	(4,000,000)	(4,000,000)	(8,000,000)	(8,000,000)
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	3,000,000	3,000,000
Interest cost	2,000,000	2,000,000	5,000,000	4,000,000
Expected return on plan assets	(8,000,000)	(7,000,000)	(16,000,000)	(14,000,000)
Amortization:
Prior service costs		0		0
Regulatory asset	0	0	0	0
Net loss	0	0	0	0
Net periodic pension cost (income)	(4,000,000)	(3,000,000)	(8,000,000)	(7,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	3,000,000	3,000,000
Interest cost	3,000,000	3,000,000	7,000,000	6,000,000
Expected return on plan assets	(6,000,000)	(6,000,000)	(13,000,000)	(13,000,000)
Amortization:
Prior service costs		0		0
Regulatory asset	0	0	0	0
Net loss	1,000,000	0	1,000,000	1,000,000
Net periodic pension cost (income)	(1,000,000)	(2,000,000)	(2,000,000)	(3,000,000)
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0	0	0
Interest cost	1,000,000	1,000,000	1,000,000	1,000,000
Expected return on plan assets	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Amortization:
Prior service costs		0		0
Regulatory asset	0	0	0	0
Net loss	0	0	0	0
Net periodic pension cost (income)	0	0	0	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 loss	0	0	0	0
Net periodic pension cost (income)	0	0	0	0
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	1,000,000	1,000,000	1,000,000
Interest cost	1,000,000	1,000,000	2,000,000	2,000,000
Expected return on plan assets	(1,000,000)	(2,000,000)	(3,000,000)	(4,000,000)
Amortization:
Prior service costs		0		0
Regulatory asset	1,000,000	1,000,000	3,000,000	3,000,000
Net loss	0	0	(1,000,000)	(1,000,000)
Net periodic pension cost (income)	$ 1,000,000	$ 1,000,000	$ 2,000,000	$ 1,000,000