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Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2025

Retirement Benefits [Abstract]

Schedule of Pension Plans and Postretirement Plans

Components of the net periodic benefit costs for the three and nine months ended September 30, 2025 and 2024 are presented in the following tables.

			Southern Company						Alabama Power						Georgia Power						Mississippi Power						Southern Power						Southern Company Gas
			(in millions)
Three Months Ended September 30, 2025
Pension Plans
Service cost			$	66					$	15					$	16					$	3					$	1					$	7
Interest cost			166						39						49						7						2						11
Expected return on plan assets			(320)						(78)						(100)						(15)						(4)						(22)
Amortization:
Prior service costs			—						—						—						—						—						(1)
Regulatory asset			—						—						—						—						—						4
Net loss			9						2						5						2						1						—
Net periodic pension income			$	(79)					$	(22)					$	(30)					$	(3)					$	—					$	(1)
Postretirement Benefits
Service cost			$	4					$	1					$	1					$	—					$	—					$	—
Interest cost			17						5						6						1						—						2
Expected return on plan assets			(23)						(8)						(9)						(1)						—						(2)
Amortization:
Prior service costs			1						—						1						—						—						—
Regulatory asset			—						—						—						—						—						1
Net gain			(4)						(2)						—						—						—						(2)
Net periodic postretirement benefit income			$	(5)					$	(4)					$	(1)					$	—					$	—					$	(1)
Nine Months Ended September 30, 2025
Pension Plans
Service cost			$	198					$	45					$	47					$	8					$	4					$	20
Interest cost			498						116						147						22						7						33
Expected return on plan assets			(960)						(234)						(298)						(44)						(12)						(65)
Amortization:
Prior service costs			—						—						1						—						—						(2)
Regulatory asset			—						—						—						—						—						11
Net (gain) loss			28						8						12						3						—						(1)
Net periodic pension income			$	(236)					$	(65)					$	(91)					$	(11)					$	(1)					$	(4)
Postretirement Benefits
Service cost			$	10					$	3					$	3					$	—					$	—					$	1
Interest cost			52						13						19						2						—						6
Expected return on plan assets			(68)						(26)						(25)						(1)						—						(7)
Amortization:
Prior service costs			2						—						1						—						—						—
Regulatory asset			—						—						—						—						—						5
Net gain			(11)						(2)						(2)						—						—						(6)
Net periodic postretirement benefit cost (income)			$	(15)					$	(12)					$	(4)					$	1					$	—					$	(1)

			Southern Company						Alabama Power						Georgia Power						Mississippi Power						Southern Power						Southern Company Gas
			(in millions)
Three Months Ended September 30, 2024
Pension Plans
Service cost			$	73					$	17					$	18					$	3					$	2					$	7
Interest cost			159						37						47						7						2						11
Expected return on plan assets			(316)						(77)						(99)						(14)						(4)						(21)
Amortization:
Prior service costs			—						—						—						—						—						(1)
Regulatory asset			—						—						—						—						—						4
Net (gain) loss			14						4						6						—						(1)						—
Net periodic pension income			$	(70)					$	(19)					$	(28)					$	(4)					$	(1)					$	—
Postretirement Benefits
Service cost			$	4					$	1					$	1					$	—					$	—					$	—
Interest cost			16						4						6						1						—						2
Expected return on plan assets			(22)						(9)						(8)						(1)						—						(2)
Amortization:
Prior service costs			1						—						1						—						—						—
Regulatory asset			—						—						—						—						—						2
Net (gain) loss			(4)						—						(3)						1						—						(1)
Net periodic postretirement benefit cost (income)			$	(5)					$	(4)					$	(3)					$	1					$	—					$	1
Nine Months Ended September 30, 2024
Pension Plans
Service cost			$	219					$	51					$	53					$	9					$	5					$	21
Interest cost			476						111						143						21						6						32
Expected return on plan assets			(947)						(230)						(296)						(43)						(12)						(64)
Amortization:
Prior service costs			—						—						1						—						—						(2)
Regulatory asset			—						—						—						—						—						11
Net loss			41						12						15						2						—						—
Net periodic pension income			$	(211)					$	(56)					$	(84)					$	(11)					$	(1)					$	(2)
Postretirement Benefits
Service cost			$	11					$	3					$	3					$	—					$	—					$	1
Interest cost			49						12						17						2						—						6
Expected return on plan assets			(66)						(26)						(24)						(1)						—						(6)
Amortization:
Prior service costs			2						—						1						—						—						—
Regulatory asset			—						—						—						—						—						5
Net gain			(12)						(2)						(4)						—						—						(4)
Net periodic postretirement benefit cost (income)			$	(16)					$	(13)					$	(7)					$	1					$	—					$	2

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- References

No definition available.

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X

- Definition

Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (q)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 715
-SubTopic 20
-Subparagraph (h)
-Name Accounting Standards Codification
-Paragraph 1
-Section 50
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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