FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Assets and liabilities measured at fair value on a recurring basis

The fair value increases (decreases) of the Funds, including unrealized gains (losses) and reinvested interest and dividends and excluding the Funds' expenses, for 2022, 2021, and 2020 are shown in the table below.

	Southern Company		Alabama Power		Georgia Power
	(in millions)
Fair value increases (decreases)
2022	$	(360)	$	(171)	$	(189)
2021	274		200		74
2020	280		142		138
Unrealized gains (losses)
At December 31, 2022	$	(391)	$	(204)	$	(187)
At December 31, 2021	(27)		(30)		3
At December 31, 2020	220		121		99

At December 31, 2022, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Energy-related derivatives(a)	$	18	$	181	$	—	$	—	$	199
Interest rate derivatives	—		12		—		—		12
Investments in trusts:(b)(c)
Domestic equity	651		178		—		—		829
Foreign equity	125		150		—		—		275
U.S. Treasury and government agency securities	—		285		—		—		285
Municipal bonds	—		51		—		—		51
Pooled funds – fixed income	—		7		—		—		7
Corporate bonds	—		412		—		—		412
Mortgage and asset backed securities	—		90		—		—		90
Private equity	—		—		—		161		161
Cash and cash equivalents	4		—		—		—		4
Other	37		12		—		—		49
Cash equivalents	1,427		20		—		—		1,447
Other investments	9		26		—		—		35
Total	$	2,271	$	1,424	$	—	$	161	$	3,856
Liabilities:
Energy-related derivatives(a)	$	32	$	178	$	—	$	—	$	210
Interest rate derivatives	—		302		—		—		302
Foreign currency derivatives	—		216		—		—		216
Contingent consideration	—		—		12		—		12
Other	—		13		—		—		13
Total	$	32	$	709	$	12	$	—	$	753

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Alabama Power
Assets:
Energy-related derivatives	$	—	$	62	$	—	$	—	$	62
Nuclear decommissioning trusts:(b)
Domestic equity	396		169		—		—		565
Foreign equity	125		—		—		—		125
U.S. Treasury and government agency securities	—		19		—		—		19
Municipal bonds	—		1		—		—		1
Corporate bonds	—		225		—		—		225
Mortgage and asset backed securities	—		22		—		—		22
Private equity	—		—		—		161		161
Other	7		—		—		—		7
Cash equivalents	438		20		—		—		458
Other investments	—		26		—		—		26
Total	$	966	$	544	$	—	$	161	$	1,671
Liabilities:
Energy-related derivatives	$	—	$	39	$	—	$	—	$	39
Georgia Power
Assets:
Energy-related derivatives	$	—	$	42	$	—	$	—	$	42
Nuclear decommissioning trusts:(b)(c)
Domestic equity	255		1		—		—		256
Foreign equity	—		149		—		—		149
U.S. Treasury and government agency securities	—		266		—		—		266
Municipal bonds	—		50		—		—		50
Corporate bonds	—		187		—		—		187
Mortgage and asset backed securities	—		68		—		—		68
Other	30		12		—		—		42
Cash equivalents	355		—		—		—		355
Total	$	640	$	775	$	—	$	—	$	1,415
Liabilities:
Energy-related derivatives	$	—	$	62	$	—	$	—	$	62

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Mississippi Power
Assets:
Energy-related derivatives	$	—	$	59	$	—	$	—	$	59
Cash equivalents	47		—		—		—		47
Total	$	47	$	59	$	—	$	—	$	106
Liabilities:
Energy-related derivatives	$	—	$	32	$	—	$	—	$	32
Southern Power
Assets:
Energy-related derivatives	$	—	$	8	$	—	$	—	$	8
Liabilities:
Energy-related derivatives	$	—	$	12	$	—	$	—	$	12
Foreign currency derivatives	—		47		—		—		47
Contingent consideration	—		—		12		—		12
Other	—		13		—		—		13
Total	$	—	$	72	$	12	$	—	$	84
Southern Company Gas
Assets:
Energy-related derivatives(a)	$	18	$	10	$	—	$	—	$	28
Non-qualified deferred compensation trusts:
Domestic equity	—		8		—		—		8
Foreign equity	—		1		—		—		1
Pooled funds - fixed income	—		7		—		—		7
Cash and cash equivalents	4		—		—		—		4
Cash equivalents	50		—		—		—		50
Total	$	72	$	26	$	—	$	—	$	98
Liabilities:
Energy-related derivatives(a)(b)	$	32	$	33	$	—	$	—	$	65
Interest rate derivatives	—		86		—		—		86
Total	$	32	$	119	$	—	$	—	$	151

(a)Excludes cash collateral of $41 million.

(b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information.

(c)Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. See Note 6 under "Nuclear Decommissioning" for additional information.

At December 31, 2021, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2021:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Energy-related derivatives(a)	$	24	$	195	$	—	$	—	$	219
Interest rate derivatives	—		19		—		—		19
Investments in trusts:(b)(c)
Domestic equity	791		225		—		—		1,016
Foreign equity	165		188		—		—		353
U.S. Treasury and government agency securities	—		314		—		—		314
Municipal bonds	—		56		—		—		56
Pooled funds – fixed income	—		13		—		—		13
Corporate bonds	1		522		—		—		523
Mortgage and asset backed securities	—		93		—		—		93
Private equity	—		—		—		150		150
Cash and cash equivalents	2		—		—		—		2
Other	22		25		—		—		47
Cash equivalents	1,160		14		—		—		1,174
Other investments	9		35		—		—		44
Total	$	2,174	$	1,699	$	—	$	150	$	4,023
Liabilities:
Energy-related derivatives(a)	$	10	$	36	$	—	$	—	$	46
Interest rate derivatives	—		29		—		—		29
Foreign currency derivatives	—		79		—		—		79
Contingent consideration	—		—		14		—		14
Other	—		13		—		—		13
Total	$	10	$	157	$	14	$	—	$	181

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2021:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Alabama Power
Assets:
Energy-related derivatives	$	—	$	55	$	—	$	—	$	55
Nuclear decommissioning trusts:(b)
Domestic equity	468		216		—		—		684
Foreign equity	165		—		—		—		165
U.S. Treasury and government agency securities	—		21		—		—		21
Municipal bonds	—		1		—		—		1
Corporate bonds	1		271		—		—		272
Mortgage and asset backed securities	—		22		—		—		22
Private equity	—		—		—		150		150
Other	9		—		—		—		9
Cash equivalents	839		14		—		—		853
Other investments	—		35		—		—		35
Total	$	1,482	$	635	$	—	$	150	$	2,267
Liabilities:
Energy-related derivatives	$	—	$	11	$	—	$	—	$	11
Georgia Power
Assets:
Energy-related derivatives	$	—	$	75	$	—	$	—	$	75
Nuclear decommissioning trusts:(b)(c)
Domestic equity	323		1		—		—		324
Foreign equity	—		185		—		—		185
U.S. Treasury and government agency securities	—		293		—		—		293
Municipal bonds	—		55		—		—		55
Corporate bonds	—		251		—		—		251
Mortgage and asset backed securities	—		71		—		—		71
Other	13		25		—		—		38
Total	$	336	$	956	$	—	$	—	$	1,292
Liabilities:
Energy-related derivatives	$	—	$	8	$	—	$	—	$	8

	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2021:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Mississippi Power
Assets:
Energy-related derivatives	$	—	$	56	$	—	$	—	$	56
Cash equivalents	40		—		—		—		40
Total	$	40	$	56	$	—	$	—	$	96
Liabilities:
Energy-related derivatives	$	—	$	5	$	—	$	—	$	5
Southern Power
Assets:
Energy-related derivatives	$	—	$	4	$	—	$	—	$	4
Liabilities:
Foreign currency derivatives	$	—	$	16	$	—	$	—	$	16
Contingent consideration	—		—		14		—		14
Other	—		13		—		—		13
Total	$	—	$	29	$	14	$	—	$	43
Southern Company Gas
Assets:
Energy-related derivatives(a)	$	24	$	5	$	—	$	—	$	29
Interest rate derivatives	—		6		—		—		6
Non-qualified deferred compensation trusts:
Domestic equity	—		8		—		—		8
Foreign equity	—		3		—		—		3
Pooled funds - fixed income	—		13		—		—		13
Cash equivalents	2		—		—		—		2
Total	$	26	$	35	$	—	$	—	$	61
Liabilities:
Energy-related derivatives(a)(b)	$	10	$	12	$	—	$	—	$	22
Interest rate derivatives	—		5		—		—		5
Total	$	10	$	17	$	—	$	—	$	27

(a)Excludes immaterial cash collateral.

(b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information.

(c)Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. See Note 6 under "Nuclear Decommissioning" for additional information.

Financial instruments not having carrying amount equal to fair value

At December 31, 2022 and 2021, other financial instruments for which the carrying amount did not equal fair value were as follows:

	Southern   Company(*)		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company  Gas(*)
	(in billions)
At December 31, 2022:
Long-term debt, including securities due within one year:
Carrying amount	$	54.6	$	10.6	$	14.7	$	1.5	$	3.0	$	7.4
Fair value	48.6		9.2		13.0		1.3		2.8		6.5
At December 31, 2021:
Long-term debt, including securities due within one year:
Carrying amount	$	52.1	$	9.7	$	13.6	$	1.5	$	3.7	$	6.9
Fair value	57.1		10.9		15.1		1.6		4.1		7.8

(*)The long-term debt of Southern Company Gas is recorded at amortized cost, including the fair value adjustments at the effective date of the 2016 merger with Southern Company. Southern Company Gas amortizes the fair value adjustments over the remaining lives of the respective bonds, the latest being through 2043.