Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2024

Retirement Benefits [Abstract]

Schedule of Pension Plans and Postretirement Plans

Components of the net periodic benefit costs for the three and six months ended June 30, 2024 and 2023 are presented in the following tables.

	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Three Months Ended June 30, 2024
Pension Plans
Service cost	$	73	$	17	$	17	$	3	$	1	$	7
Interest cost	158		37		48		7		2		11
Expected return on plan assets	(315)		(76)		(98)		(15)		(4)		(21)
Amortization:
Prior service costs	—		—		1		—		—		(1)
Regulatory asset	—		—		—		—		—		4
Net loss	13		4		4		2		1		—
Net periodic pension income	$	(71)	$	(18)	$	(28)	$	(3)	$	—	$	—
Postretirement Benefits
Service cost	$	3	$	1	$	1	$	—	$	—	$	—
Interest cost	17		4		5		—		—		2
Expected return on plan assets	(22)		(8)		(8)		—		—		(2)
Amortization:
Regulatory asset	—		—		—		—		—		2
Net gain	(4)		(2)		—		—		—		(1)
Net periodic postretirement benefit cost (income)	$	(6)	$	(5)	$	(2)	$	—	$	—	$	1
Six Months Ended June 30, 2024
Pension Plans
Service cost	$	146	$	34	$	35	$	6	$	3	$	14
Interest cost	317		74		96		14		4		21
Expected return on plan assets	(631)		(153)		(197)		(29)		(8)		(43)
Amortization:
Prior service costs	—		—		1		—		—		(1)
Regulatory asset	—		—		—		—		—		8
Net loss	27		8		9		2		1		—
Net periodic pension income	$	(141)	$	(37)	$	(56)	$	(7)	$	—	$	(1)
Postretirement Benefits
Service cost	$	7	$	2	$	2	$	—	$	—	$	—
Interest cost	33		8		11		1		—		4
Expected return on plan assets	(44)		(17)		(16)		—		—		(4)
Amortization:
Prior service costs	1		—		—		—		—		—
Regulatory asset	—		—		—		—		—		3
Net gain	(8)		(2)		(1)		(1)		—		(3)
Net periodic postretirement benefit income	$	(11)	$	(9)	$	(4)	$	—	$	—	$	—

	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Three Months Ended June 30, 2023
Pension Plans
Service cost	$	69	$	16	$	17	$	3	$	1	$	6
Interest cost	157		36		47		7		2		11
Expected return on plan assets	(308)		(74)		(96)		(14)		(4)		(22)
Amortization:
Prior service costs	—		—		1		—		—		(1)
Regulatory asset	—		—		—		—		—		4
Net (gain)/loss	8		3		3		—		—		(1)
Net periodic pension income	$	(74)	$	(19)	$	(28)	$	(4)	$	(1)	$	(3)
Postretirement Benefits
Service cost	$	3	$	1	$	1	$	—	$	—	$	—
Interest cost	17		4		7		1		—		2
Expected return on plan assets	(20)		(9)		(8)		—		—		(2)
Amortization:
Prior service costs	1		—		—		—		—		—
Regulatory asset	—		—		—		—		—		2
Net gain	(3)		—		(1)		—		—		(1)
Net periodic postretirement benefit cost (income)	$	(2)	$	(4)	$	(1)	$	1	$	—	$	1
Six Months Ended June 30, 2023
Pension Plans
Service cost	$	138	$	32	$	34	$	6	$	3	$	12
Interest cost	313		72		95		14		4		21
Expected return on plan assets	(615)		(148)		(192)		(28)		(8)		(44)
Amortization:
Prior service costs	—		—		1		—		—		(1)
Regulatory asset	—		—		—		—		—		8
Net (gain) loss	16		5		6		—		—		(2)
Net periodic pension income	$	(148)	$	(39)	$	(56)	$	(8)	$	(1)	$	(6)
Postretirement Benefits
Service cost	$	7	$	2	$	2	$	—	$	—	$	—
Interest cost	35		8		13		2		—		4
Expected return on plan assets	(41)		(17)		(15)		(1)		—		(3)
Amortization:
Prior service costs	1		—		—		—		—		—
Regulatory asset	—		—		—		—		—		3
Net gain	(6)		(1)		(2)		—		—		(2)
Net periodic postretirement benefit cost (income)	$	(4)	$	(8)	$	(2)	$	1	$	—	$	2