v3.23.3
Retirement Benefits
 9 Months Ended
Sep. 30, 2023
Retirement Benefits [Abstract]  
Retirement Benefits RETIREMENT BENEFITS
The Southern Company system has a qualified defined benefit, trusteed, pension plan covering substantially all employees, with the exception of employees at PowerSecure. The qualified pension plan is funded in accordance with requirements of the Employee Retirement Income Security Act of 1974, as amended (ERISA). No mandatory contributions to the qualified pension plan are anticipated for the year ending December 31, 2023. The Southern Company system also provides certain non-qualified defined benefits for a select group of management and highly compensated employees, which are funded on a cash basis. In addition, the Southern Company system provides certain medical care and life insurance benefits for retired employees through other postretirement benefit plans. The traditional electric operating companies fund other postretirement trusts to the extent required by their respective regulatory commissions. Southern Company Gas has a separate unfunded supplemental retirement health care plan that provides medical care and life insurance benefits to employees of discontinued businesses.
See Note 11 to the financial statements in Item 8 of the Form 10-K for additional information.
On each Registrant's condensed statements of income, the service cost component of net periodic benefit costs is included in other operations and maintenance expenses and all other components of net periodic benefit costs are included in other income (expense), net. Components of the net periodic benefit costs for the three and nine months ended September 30, 2023 and 2022 are presented in the following tables.
Southern
Company		Alabama
Power		Georgia
Power		Mississippi
Power		Southern PowerSouthern Company Gas
(in millions)
Three Months Ended September 30, 2023
Pension Plans
Service cost$69 $16 $17 $2 $2 $6 
Interest cost156 37 48 7 2 11 
Expected return on plan assets(307)(75)(97)(13)(4)(22)
Amortization:
Prior service costs— — — — — (1)
Regulatory asset— — — — — 4 
Net (gain) loss8 2 4 1 — (1)
Net periodic pension income$(74)$(20)$(28)$(3)$— $(3)
Postretirement Benefits
Service cost$4 $1 $1 $— $— $— 
Interest cost18 5 6 1 — 2 
Expected return on plan assets(21)(9)(7)(1)— (2)
Amortization:
Prior service costs— — 1 — — — 
Regulatory asset— — — — — 2 
Net gain(4)(1)(1)— — (1)
Net periodic postretirement benefit cost (income)$(3)$(4)$— $— $— $1 
Nine Months Ended September 30, 2023
Pension Plans
Service cost$207 $48 $51 $8 $5 $18 
Interest cost469 109 143 21 6 32 
Expected return on plan assets(922)(223)(289)(41)(12)(65)
Amortization:
Prior service costs— — 1 — — (2)
Regulatory asset— — — — — 11 
Net (gain) loss24 7 10 1 — (3)
Net periodic pension income$(222)$(59)$(84)$(11)$(1)$(9)
Postretirement Benefits
Service cost$11 $3 $3 $— $— $1 
Interest cost53 13 19 2 — 6 
Expected return on plan assets(62)(26)(22)(1)— (5)
Amortization:
Prior service costs1 — 1 — — — 
Regulatory asset— — — — — 5 
Net gain(10)(2)(3)— — (3)
Net periodic postretirement benefit cost (income)$(7)$(12)$(2)$1 $— $4 
Southern
Company		Alabama
Power		Georgia
Power		Mississippi
Power		Southern PowerSouthern Company Gas
(in millions)
Three Months Ended September 30, 2022
Pension Plans
Service cost$103 $25 $26 $5 $2 $9 
Interest cost102 24 31 5 2 7 
Expected return on plan assets(316)(77)(99)(15)(4)(22)
Amortization:
Prior service costs— — — — — (1)
Regulatory asset— — — — — 3 
Net loss60 16 18 2 1 2 
Net periodic pension cost (income)$(51)$(12)$(24)$(3)$1 $(2)
Postretirement Benefits
Service cost$6 $2 $2 $1 $1 $— 
Interest cost10 3 4 — — 1 
Expected return on plan assets(20)(9)(8)— — (2)
Amortization:
Prior service costs(1)— — — — — 
Regulatory asset— — — — — 2 
Net (gain)/loss1 — — — — (1)
Net periodic postretirement benefit cost (income)$(4)$(4)$(2)$1 $1 $— 
Nine Months Ended September 30, 2022
Pension Plans
Service cost$309 $74 $78 $13 $7 $26 
Interest cost306 72 92 14 5 21 
Expected return on plan assets(949)(229)(298)(44)(12)(68)
Amortization:
Prior service costs— — 1 — — (2)
Regulatory asset— — — — — 11 
Net loss180 47 55 9 2 5 
Net periodic pension cost (income)$(154)$(36)$(72)$(8)$2 $(7)
Postretirement Benefits
Service cost$17 $5 $5 $1 $1 $1 
Interest cost31 8 11 1 — 4 
Expected return on plan assets(60)(25)(21)(1)— (6)
Amortization:
Prior service costs(1)— — — — — 
Regulatory asset— — — — — 5 
Net (gain) loss1 — 1 — — (2)
Net periodic postretirement benefit cost (income)$(12)$(12)$(4)$1 $1 $2