Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2023

Retirement Benefits [Abstract]

Schedule of Pension Plans and Postretirement Plans

Components of the net periodic benefit costs for the three months ended March 31, 2023 and 2022 are presented in the following tables.

	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Three Months Ended March 31, 2023
Pension Plans
Service cost	$	69	$	16	$	17	$	3	$	2	$	6
Interest cost	156		36		48		7		2		11
Expected return on plan assets	(307)		(74)		(96)		(14)		(4)		(22)
Amortization:
Prior service costs	—		—		—		—		—		(1)
Regulatory asset	—		—		—		—		—		4
Net (gain) loss	8		2		3		—		—		(1)
Net periodic pension income	$	(74)	$	(20)	$	(28)	$	(4)	$	—	$	(3)
Postretirement Benefits
Service cost	$	4	$	1	$	1	$	—	$	—	$	—
Interest cost	18		4		6		1		—		2
Expected return on plan assets	(21)		(8)		(7)		(1)		—		(2)
Amortization:
Regulatory asset	—		—		—		—		—		2
Net gain	(3)		(1)		(1)		—		—		(1)
Net periodic postretirement benefit cost (income)	$	(2)	$	(4)	$	(1)	$	—	$	—	$	1

	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Three Months Ended March 31, 2022
Pension Plans
Service cost	$	103	$	25	$	26	$	4	$	2	$	9
Interest cost	102		24		31		5		2		7
Expected return on plan assets	(316)		(77)		(99)		(15)		(4)		(22)
Amortization:
Prior service costs	—		—		—		—		—		(1)
Regulatory asset	—		—		—		—		—		4
Net loss	60		16		18		3		1		2
Net periodic pension cost (income)	$	(51)	$	(12)	$	(24)	$	(3)	$	1	$	(1)
Postretirement Benefits
Service cost	$	6	$	1	$	2	$	—	$	—	$	—
Interest cost	10		3		4		—		—		1
Expected return on plan assets	(20)		(8)		(7)		—		—		(2)
Amortization:
Regulatory asset	—		—		—		—		—		2
Net periodic postretirement benefit cost (income)	$	(4)	$	(4)	$	(1)	$	—	$	—	$	1