Southern Power 10-Q 29 Oct 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2020shares
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	1-3526
Entity Registrant Name	The Southern Company
Entity Tax Identification Number	58-0690070
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	30 Ivan Allen Jr. Boulevard, N.W.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30308
City Area Code	404
Local Phone Number	506-5000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	1,056,241,993
Entity Central Index Key	0000092122
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Emerging Growth Company	false
Entity Small Business	false
Common Stock, par value $5 per share
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $5 per share
Trading Symbol	SO
Security Exchange Name	NYSE
Series 2015A 6.25% Junior Subordinated Notes due 2075
Document Information [Line Items]
Title of 12(b) Security	Series 2015A 6.25% Junior Subordinated Notes due 2075
Trading Symbol	SOJA
Security Exchange Name	NYSE
Series 2016A 5.25% Junior Subordinated Notes due 2076
Document Information [Line Items]
Title of 12(b) Security	Series 2016A 5.25% Junior Subordinated Notes due 2076
Trading Symbol	SOJB
Security Exchange Name	NYSE
Series 2017B 5.25% Junior Subordinated Notes due 2077
Document Information [Line Items]
Title of 12(b) Security	Series 2017B 5.25% Junior Subordinated Notes due 2077
Trading Symbol	SOJC
Security Exchange Name	NYSE
2019 Series A Corporate Units
Document Information [Line Items]
Title of 12(b) Security	2019 Series A Corporate Units
Trading Symbol	SOLN
Security Exchange Name	NYSE
Series 2020A 4.95% Junior Subordinated Notes due 2080
Document Information [Line Items]
Title of 12(b) Security	Series 2020A 4.95% Junior Subordinated Notes due 2080
Trading Symbol	SOJD
Security Exchange Name	NYSE
Series 2020C 4.20% Junior Subordinated Notes due 2060
Document Information [Line Items]
Title of 12(b) Security	Series 2020C 4.20% Junior Subordinated Notes due 2060
Trading Symbol	SOJE
Security Exchange Name	NYSE
ALABAMA POWER CO
Document Information [Line Items]
Entity File Number	1-3164
Entity Registrant Name	Alabama Power Company
Entity Tax Identification Number	63-0004250
Entity Incorporation, State or Country Code	AL
Entity Address, Address Line One	600 North 18th Street
Entity Address, City or Town	Birmingham
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35203
City Area Code	205
Local Phone Number	257-1000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	30,537,500
Entity Central Index Key	0000003153
Entity Emerging Growth Company	false
Entity Small Business	false
ALABAMA POWER CO | 5.00% Series Class A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	5.00% Series Class A Preferred Stock
Trading Symbol	ALP PR Q
Security Exchange Name	NYSE
GEORGIA POWER CO
Document Information [Line Items]
Entity File Number	1-6468
Entity Registrant Name	Georgia Power Company
Entity Tax Identification Number	58-0257110
Entity Incorporation, State or Country Code	GA
Entity Address, Address Line One	241 Ralph McGill Boulevard, N.E.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30308
City Area Code	404
Local Phone Number	506-6526
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	9,261,500
Entity Central Index Key	0000041091
Entity Emerging Growth Company	false
Entity Small Business	false
GEORGIA POWER CO | Series 2017A 5.00% Junior Subordinated Notes due 2077
Document Information [Line Items]
Title of 12(b) Security	Series 2017A 5.00% Junior Subordinated Notes due 2077
Trading Symbol	GPJA
Security Exchange Name	NYSE
MISSISSIPPI POWER CO
Document Information [Line Items]
Entity File Number	001-11229
Entity Registrant Name	Mississippi Power Company
Entity Tax Identification Number	64-0205820
Entity Incorporation, State or Country Code	MS
Entity Address, Address Line One	2992 West Beach Boulevard
Entity Address, City or Town	Gulfport
Entity Address, State or Province	MS
Entity Address, Postal Zip Code	39501
City Area Code	228
Local Phone Number	864-1211
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	1,121,000
Entity Central Index Key	0000066904
Entity Emerging Growth Company	false
Entity Small Business	false
SOUTHERN POWER CO
Document Information [Line Items]
Entity File Number	001-37803
Entity Registrant Name	Southern Power Company
Entity Tax Identification Number	58-2598670
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	30 Ivan Allen Jr. Boulevard, N.W.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30308
City Area Code	404
Local Phone Number	506-5000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	1,000
Entity Central Index Key	0001160661
Entity Emerging Growth Company	false
Entity Small Business	false
SOUTHERN POWER CO | Series 2016A 1.000% Senior Notes due 2022
Document Information [Line Items]
Title of 12(b) Security	Series 2016A 1.000% Senior Notes due 2022
Trading Symbol	SO/22B
Security Exchange Name	NYSE
SOUTHERN POWER CO | Series 2016B 1.850% Senior Notes due 2026
Document Information [Line Items]
Title of 12(b) Security	Series 2016B 1.850% Senior Notes due 2026
Trading Symbol	SO/26A
Security Exchange Name	NYSE
SOUTHERN Co GAS
Document Information [Line Items]
Entity File Number	1-14174
Entity Registrant Name	Southern Company Gas
Entity Tax Identification Number	58-2210952
Entity Incorporation, State or Country Code	GA
Entity Address, Address Line One	Ten Peachtree Place, N.E.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30309
City Area Code	404
Local Phone Number	584-4000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	100
Entity Central Index Key	0001004155
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenues:
Operating revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Operating Expenses:
Total cost of sales	71	79	654	956
Other operations and maintenance	1,286	1,296	3,785	3,898
Depreciation and amortization	889	760	2,619	2,267
Taxes other than income taxes	304	303	932	931
Estimated loss on Plant Vogtle Units 3 and 4	0	0	149	0
Impairment charges	0	110	0	142
(Gain) loss on dispositions, net	0	(6)	(39)	(2,512)
Total operating expenses	3,785	3,982	11,102	9,459
Operating Income (Loss)	1,835	2,013	4,156	7,046
Other Income and (Expense):
Allowance for equity funds used during construction	38	33	106	96
Earnings from equity method investments	33	39	105	120
Interest expense, net of amounts capitalized	(443)	(434)	(1,343)	(1,294)
Impairment of leveraged lease	0	0	(154)	0
Other income (expense), net	113	61	319	239
Total other income and (expense)	(259)	(301)	(967)	(839)
Earnings (Loss) Before Income Taxes	1,576	1,712	3,189	6,207
Income taxes (benefit)	293	367	443	1,872
Consolidated Net Income	1,283	1,345	2,746	4,335
Dividends on preferred stock of subsidiaries	4	4	11	11
Net income attributable to noncontrolling interests	28	25	3	26
Net Income	$ 1,251	$ 1,316	$ 2,732	$ 4,298
Earnings per share -
Basic (in dollars per share)	$ 1.18	$ 1.26	$ 2.58	$ 4.12
Diluted (in dollars per share)	$ 1.18	$ 1.25	$ 2.57	$ 4.09
Average number of shares of common stock outstanding (in millions)
Basic (in shares)	1,058	1,048	1,058	1,043
Diluted (in shares)	1,064	1,057	1,064	1,051
Cost, Product and Service [Extensible List]			us-gaap:NaturalGasUsRegulatedMember
Retail electric revenues
Operating Revenues:
Operating revenues	$ 4,243	$ 4,512	$ 10,503	$ 11,136
Wholesale electric revenues
Operating Revenues:
Operating revenues	584	625	1,473	1,667
Other electric revenues
Operating Revenues:
Operating revenues	164	163	484	492
Natural gas
Operating Revenues:
Operating revenues	477	498	2,362	2,661
Operating Expenses:
Total cost of sales	71	79	654	956
Other
Operating Revenues:
Operating revenues	152	197	436	549
Operating Expenses:
Total cost of sales	72	114	201	316
Fuel
Operating Expenses:
Total cost of sales	933	1,072	2,190	2,836
Purchased power
Operating Expenses:
Total cost of sales	230	254	611	625
Alternative revenue programs
Operating Revenues:
Operating revenues	(1)	0	6	0
ALABAMA POWER CO
Operating Revenues:
Operating revenues	1,729	1,841	4,445	4,762
Operating Expenses:
Other operations and maintenance	387	409	1,078	1,221
Depreciation and amortization	205	195	606	593
Taxes other than income taxes	103	101	311	301
Total operating expenses	1,109	1,165	2,962	3,303
Operating Income (Loss)	620	676	1,483	1,459
Other Income and (Expense):
Allowance for equity funds used during construction	12	13	34	41
Interest expense, net of amounts capitalized	(84)	(83)	(255)	(248)
Other income (expense), net	30	11	78	36
Total other income and (expense)	(42)	(59)	(143)	(171)
Earnings (Loss) Before Income Taxes	578	617	1,340	1,288
Income taxes (benefit)	130	144	307	295
Consolidated Net Income	448	473	1,033	993
Dividends on preferred stock of subsidiaries	4	4	11	11
Net Income	444	469	1,022	982
ALABAMA POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	1,575	1,694	4,003	4,286
ALABAMA POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	73	71	184	194
ALABAMA POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	11	2	36	66
ALABAMA POWER CO | Other
Operating Revenues:
Operating revenues	70	74	222	216
ALABAMA POWER CO | Fuel
Operating Expenses:
Total cost of sales	306	310	721	864
ALABAMA POWER CO | Purchased power
Operating Expenses:
Total cost of sales	64	77	153	160
ALABAMA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of sales	44	73	93	164
GEORGIA POWER CO
Operating Revenues:
Operating revenues	2,617	2,755	6,371	6,706
Operating Expenses:
Other operations and maintenance	483	473	1,411	1,385
Depreciation and amortization	358	250	1,064	733
Taxes other than income taxes	123	127	344	348
Estimated loss on Plant Vogtle Units 3 and 4	0	0	149	0
Total operating expenses	1,620	1,594	4,596	4,451
Operating Income (Loss)	997	1,161	1,775	2,255
Other Income and (Expense):
Allowance for equity funds used during construction			63	49
Interest expense, net of amounts capitalized	(106)	(103)	(322)	(304)
Other income (expense), net	54	36	156	113
Total other income and (expense)	(52)	(67)	(166)	(191)
Earnings (Loss) Before Income Taxes	945	1,094	1,609	2,064
Income taxes (benefit)	172	255	198	466
Consolidated Net Income	773	839	1,411	1,598
GEORGIA POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	2,435	2,567	5,870	6,181
GEORGIA POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	34	39	85	107
GEORGIA POWER CO | Other
Operating Revenues:
Operating revenues	148	149	416	418
GEORGIA POWER CO | Fuel
Operating Expenses:
Total cost of sales	368	443	826	1,132
GEORGIA POWER CO | Purchased power
Operating Expenses:
Total cost of sales	146	151	409	393
GEORGIA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of sales	142	150	393	460
MISSISSIPPI POWER CO
Operating Revenues:
Operating revenues	336	370	895	970
Operating Expenses:
Other operations and maintenance	62	72	202	204
Depreciation and amortization	47	48	135	144
Taxes other than income taxes	31	30	90	85
Total operating expenses	249	277	711	767
Operating Income (Loss)	87	93	184	203
Other Income and (Expense):
Interest expense, net of amounts capitalized	(14)	(17)	(45)	(52)
Other income (expense), net	6	4	19	15
Total other income and (expense)	(8)	(13)	(26)	(37)
Earnings (Loss) Before Income Taxes	79	80	158	166
Income taxes (benefit)	12	15	20	27
Consolidated Net Income	67	65	138	139
MISSISSIPPI POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	232	251	630	669
MISSISSIPPI POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	61	64	164	178
MISSISSIPPI POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	36	51	82	109
MISSISSIPPI POWER CO | Other
Operating Revenues:
Operating revenues	7	4	19	14
MISSISSIPPI POWER CO | Fuel
Operating Expenses:
Total cost of sales	103	121	266	319
MISSISSIPPI POWER CO | Purchased power
Operating Expenses:
Total cost of sales	6	6	18	15
SOUTHERN POWER CO
Operating Revenues:
Operating revenues	523	574	1,337	1,527
Operating Expenses:
Other operations and maintenance	89	85	245	250
Depreciation and amortization	129	120	367	357
Taxes other than income taxes	10	10	29	32
(Gain) loss on dispositions, net	0	0	(39)	(23)
Total operating expenses	384	407	1,000	1,147
Operating Income (Loss)	139	167	337	380
Other Income and (Expense):
Interest expense, net of amounts capitalized	(36)	(43)	(114)	(127)
Other income (expense), net	13	6	19	48
Total other income and (expense)	(23)	(37)	(95)	(79)
Earnings (Loss) Before Income Taxes	116	130	242	301
Income taxes (benefit)	14	19	27	(41)
Consolidated Net Income	102	111	215	342
Net income attributable to noncontrolling interests	28	25	3	26
Net Income	74	86	212	316
SOUTHERN POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	418	455	1,047	1,197
SOUTHERN POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	101	116	279	320
SOUTHERN POWER CO | Other
Operating Revenues:
Operating revenues	4	3	11	10
SOUTHERN POWER CO | Fuel
Operating Expenses:
Total cost of sales	137	166	346	449
SOUTHERN POWER CO | Purchased power
Operating Expenses:
Total cost of sales	19	26	52	82
SOUTHERN Co GAS
Operating Revenues:
Operating revenues	477	498	2,362	2,661
Operating Expenses:
Other operations and maintenance	217	208	696	642
Depreciation and amortization	125	121	368	359
Taxes other than income taxes	35	33	154	161
Impairment charges	0	92	0	92
Total operating expenses	448	533	1,872	2,210
Operating Income (Loss)	29	(35)	490	451
Other Income and (Expense):
Earnings from equity method investments	33	35	106	115
Interest expense, net of amounts capitalized	(57)	(56)	(171)	(174)
Other income (expense), net	12	5	33	16
Total other income and (expense)	(12)	(16)	(32)	(43)
Earnings (Loss) Before Income Taxes	17	(51)	458	408
Income taxes (benefit)	3	(22)	98	61
Consolidated Net Income	14	(29)	360	347
Net Income	14	(29)	360	347
SOUTHERN Co GAS | Natural gas
Operating Revenues:
Operating revenues	478	498	2,356	2,661
Operating Expenses:
Total cost of sales	71	79	654	956
SOUTHERN Co GAS | Alternative revenue programs
Operating Revenues:
Operating revenues	$ (1)	$ 0	$ 6	$ 0

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Cost, Product and Service [Extensible List]			us-gaap:NaturalGasUsRegulatedMember
Alternative revenue programs
Revenues	(1)	0	$ 6	0
SOUTHERN Co GAS
Revenues	477	498	2,362	2,661
Revenue taxes collected	10	10	79	88
SOUTHERN Co GAS | Alternative revenue programs
Revenues	$ (1)	$ 0	$ 6	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net income	$ 1,283	$ 1,345	$ 2,746	$ 4,335
Qualifying hedges:
Changes in fair value, net of tax	49	(92)	(26)	(152)
Reclassification adjustment for amounts included in net income, net of tax	(32)	50	(3)	74
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	3	1	6	2
Total other comprehensive income (loss)	20	(41)	(23)	(76)
Comprehensive Income	1,303	1,304	2,723	4,259
Dividends on preferred stock of subsidiaries	4	4	11	11
Comprehensive income attributable to noncontrolling interests	28	25	3	26
Comprehensive Income (Loss) Attributable to Parent	1,271	1,275	2,709	4,222
ALABAMA POWER CO
Net income	448	473	1,033	993
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax	1	1	3	3
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	1	1	3	3
Comprehensive Income	449	474	1,036	996
Dividends on preferred stock of subsidiaries	4	4	11	11
GEORGIA POWER CO
Net income	773	839	1,411	1,598
Qualifying hedges:
Changes in fair value, net of tax	0	(35)	(2)	(62)
Reclassification adjustment for amounts included in net income, net of tax	2	0	4	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	2	(35)	2	(61)
Comprehensive Income	775	804	1,413	1,537
MISSISSIPPI POWER CO
Net income	67	65	138	139
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax	0	0	1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	0	0	1	1
Comprehensive Income	67	65	139	140
SOUTHERN POWER CO
Net income	102	111	215	342
Qualifying hedges:
Changes in fair value, net of tax	44	(53)	(6)	(84)
Reclassification adjustment for amounts included in net income, net of tax	(36)	45	(24)	64
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0	0	2	0
Total other comprehensive income (loss)	8	(8)	(28)	(20)
Comprehensive Income	110	103	187	322
Comprehensive income attributable to noncontrolling interests	28	25	3	26
Comprehensive Income (Loss) Attributable to Parent	82	78	184	296
SOUTHERN Co GAS
Net income	14	(29)	360	347
Qualifying hedges:
Changes in fair value, net of tax	4	(3)	(17)	(6)
Reclassification adjustment for amounts included in net income, net of tax	1	0	7	0
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0	0	0	(1)
Total other comprehensive income (loss)	5	(3)	(10)	(7)
Comprehensive Income	$ 19	$ (32)	$ 350	$ 340

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Qualifying hedges:
Changes in fair value, tax	$ 17	$ (33)	$ (9)	$ (54)
Reclassification adjustment for amounts included in net income, tax	(11)	17	(1)	25
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	(1)	0	(3)	0
ALABAMA POWER CO
Qualifying hedges:
Reclassification adjustment for amounts included in net income, tax	0	0	1	1
GEORGIA POWER CO
Qualifying hedges:
Changes in fair value, tax	0	(12)	(1)	(21)
Reclassification adjustment for amounts included in net income, tax	0	0	2	0
MISSISSIPPI POWER CO
Qualifying hedges:
Reclassification adjustment for amounts included in net income, tax	0	0	0	0
SOUTHERN POWER CO
Qualifying hedges:
Changes in fair value, tax	15	(18)	(2)	(28)
Reclassification adjustment for amounts included in net income, tax	(13)	15	(8)	21
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	0	0	0	0
SOUTHERN Co GAS
Qualifying hedges:
Changes in fair value, tax	1	(3)	(6)	(4)
Reclassification adjustment for amounts included in net income, tax	0	0	2	0
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	$ 0	$ 0	$ 1	$ (1)

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating Activities:
Net income	$ 2,746	$ 4,335
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	2,903	2,514
Deferred income taxes	(196)	253
Utilization of federal investment tax credits	319	722
Allowance for equity funds used during construction	(106)	(96)
Impairment charges	0	142
Pension, postretirement, and other employee benefits	(190)	(114)
Settlement of asset retirement obligations	(315)	(225)
Stock based compensation expense	99	87
Estimated loss on Plant Vogtle Units 3 and 4	149	0
Storm damage reserve accruals	171	34
Impairment charges	154	0
(Gain) loss on dispositions, net	(36)	(2,517)
Other, net	93	(20)
Changes in certain current assets and liabilities —
-Receivables	125	588
-Prepayments	(39)	61
-Materials and supplies	(141)	(31)
-Other current assets	(80)	(31)
-Accounts payable	(428)	(1,155)
-Accrued taxes	289	679
-Accrued compensation	(183)	(191)
-Retail fuel cost over recovery	158	31
-Customer refunds	(226)	(30)
-Other current liabilities	(46)	(155)
Net cash provided from operating activities	5,220	4,881
Investing Activities:
Property additions	(5,365)	(5,417)
Nuclear decommissioning trust fund purchases	(714)	(683)
Nuclear decommissioning trust fund sales	708	678
Proceeds from dispositions and asset sales	987	5,036
Cost of removal, net of salvage	(233)	(290)
Change in construction payables, net	(40)	(132)
Investment in unconsolidated subsidiaries	(79)	(141)
Payments pursuant to LTSAs	(139)	(139)
Other investing activities	(17)	15
Net cash used for investing activities	(4,892)	(1,073)
Financing Activities:
Decrease in notes payable, net	(1,534)	(773)
Proceeds —
Long-term debt	7,543	4,737
Common stock	63	623
Short-term borrowings	615	250
Redemptions and repurchases —
Long-term debt	(2,472)	(3,216)
Short-term borrowings	(840)	(1,850)
Distributions to noncontrolling interests	(164)	(125)
Capital contributions from noncontrolling interests	173	11
Purchase of membership interests from noncontrolling interests	(60)	0
Payment of common stock dividends	(2,008)	(1,919)
Other financing activities	(239)	(130)
Net cash provided from (used for) financing activities	1,077	(2,392)
Net Change in Cash, Cash Equivalents, and Restricted Cash	1,405	1,416
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1,978	1,519
Cash, Cash Equivalents, and Restricted Cash at End of Period	3,383	2,935
Cash paid during the period for —
Interest, net of amounts capitalized	1,346	1,318
Income taxes, net	66	265
Accrued property additions at end of period	917	953
Right-of-use assets obtained under operating leases	158	76
Right-of-use assets obtained under finance leases	8	31
Interest capitalized	61	55
ALABAMA POWER CO
Operating Activities:
Net income	1,033	993
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	731	756
Deferred income taxes	71	148
Allowance for equity funds used during construction	(34)	(41)
Pension, postretirement, and other employee benefits	(71)	(30)
Settlement of asset retirement obligations	(157)	(76)
Other, net	69	18
Changes in certain current assets and liabilities —
-Receivables	(130)	(115)
-Prepayments	(32)	(30)
-Materials and supplies	(55)	11
-Other current assets	(32)	(30)
-Accounts payable	(248)	(267)
-Accrued taxes	142	149
-Accrued compensation	(55)	(55)
-Retail fuel cost over recovery	74	21
-Customer refunds	(64)	(28)
-Other current liabilities	(13)	47
Net cash provided from operating activities	1,229	1,471
Investing Activities:
Property additions	(1,460)	(1,239)
Nuclear decommissioning trust fund purchases	(213)	(201)
Nuclear decommissioning trust fund sales	213	201
Cost of removal, net of salvage	(68)	(79)
Change in construction payables, net	(46)	(99)
Other investing activities	(17)	(22)
Net cash used for investing activities	(1,591)	(1,439)
Proceeds —
Senior notes	600	600
Pollution control revenue bonds	87	0
Capital contributions from parent company	649	1,252
Redemptions and repurchases —
Pollution control revenue bonds	(87)	0
Senior notes	0	(200)
Payment of common stock dividends	(718)	(633)
Other financing activities	(26)	(27)
Net cash provided from (used for) financing activities	505	992
Net Change in Cash, Cash Equivalents, and Restricted Cash	143	1,024
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	894	313
Cash, Cash Equivalents, and Restricted Cash at End of Period	1,037	1,337
Cash paid during the period for —
Interest, net of amounts capitalized	249	246
Income taxes, net	203	89
Accrued property additions at end of period	154	173
Right-of-use assets obtained under operating leases	63	7
Right-of-use assets obtained under finance leases	2	1
Interest capitalized	11	15
GEORGIA POWER CO
Operating Activities:
Net income	1,411	1,598
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	1,206	887
Deferred income taxes	(167)	145
Allowance for equity funds used during construction	(63)	(49)
Pension, postretirement, and other employee benefits	(98)	(85)
Settlement of asset retirement obligations	(130)	(110)
Estimated loss on Plant Vogtle Units 3 and 4	149	0
Storm damage reserve accruals	160	22
Other, net	12	40
Changes in certain current assets and liabilities —
-Receivables	(168)	(128)
-Prepaid income taxes	0	102
-Materials and supplies	(74)	(2)
-Contract assets	(34)	(33)
-Other current assets	(31)	(13)
-Accounts payable	25	(134)
-Accrued taxes	44	138
-Accrued compensation	(36)	(12)
-Retail fuel cost over recovery	84	0
-Customer refunds	(162)	18
-Other current liabilities	(3)	(19)
Net cash provided from operating activities	2,125	2,365
Investing Activities:
Property additions	(2,519)	(2,581)
Nuclear decommissioning trust fund purchases	(500)	(483)
Nuclear decommissioning trust fund sales	495	477
Proceeds from dispositions and asset sales	143	9
Cost of removal, net of salvage	(93)	(136)
Change in construction payables, net	(14)	(75)
Payments pursuant to LTSAs	(44)	(17)
Other investing activities	6	13
Net cash used for investing activities	(2,526)	(2,793)
Financing Activities:
Decrease in notes payable, net	(115)	(294)
Proceeds —
FFB loan	519	835
Senior notes	1,500	750
Pollution control revenue bonds	53	584
Short-term borrowings	250	250
Capital contributions from parent company	1,379	82
Redemptions and repurchases —
Short-term borrowings	(375)	0
Pollution control revenue bonds	(148)	(223)
Senior notes	(950)	0
FFB loan	(55)	0
Payment of common stock dividends	(1,156)	(1,182)
Other financing activities	(35)	(37)
Net cash provided from (used for) financing activities	867	765
Net Change in Cash, Cash Equivalents, and Restricted Cash	466	337
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	52	112
Cash, Cash Equivalents, and Restricted Cash at End of Period	518	449
Cash paid during the period for —
Interest, net of amounts capitalized	316	296
Income taxes, net	311	45
Accrued property additions at end of period	523	589
Right-of-use assets obtained under operating leases	30	18
Right-of-use assets obtained under finance leases	0	24
Interest capitalized	34	25
MISSISSIPPI POWER CO
Operating Activities:
Net income	138	139
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	142	148
Deferred income taxes	(19)	10
Settlement of asset retirement obligations	(16)	(28)
Other, net	9	8
Changes in certain current assets and liabilities —
-Receivables	(3)	(11)
-Other current assets	(7)	18
-Accounts payable	(54)	(26)
-Accrued taxes	15	(12)
-Accrued compensation	(8)	(10)
-Other current liabilities	(11)	6
Net cash provided from operating activities	186	242
Investing Activities:
Property additions	(174)	(134)
Change in construction payables, net	7	(16)
Payments pursuant to LTSAs	(20)	(18)
Other investing activities	(13)	(30)
Net cash used for investing activities	(200)	(198)
Proceeds —
Pollution control revenue bonds	34	43
Short-term borrowings	40	0
Capital contributions from parent company	80	2
Other long-term debt	100	0
Redemptions and repurchases —
Short-term borrowings	(40)	0
Pollution control revenue bonds	(41)	0
Senior notes	(275)	0
Return of capital to parent company	(74)	(113)
Payment of common stock dividends	(37)	0
Other financing activities	(1)	(1)
Net cash provided from (used for) financing activities	(214)	(69)
Net Change in Cash, Cash Equivalents, and Restricted Cash	(228)	(25)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	286	293
Cash, Cash Equivalents, and Restricted Cash at End of Period	58	268
Cash paid during the period for —
Interest, net of amounts capitalized	49	55
Income taxes, net	9	0
Accrued property additions at end of period	42	20
Interest capitalized	0	1
SOUTHERN POWER CO
Operating Activities:
Net income	215	342
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	386	377
Deferred income taxes	(59)	(122)
Utilization of federal investment tax credits	318	705
Amortization of investment tax credits	(44)	(136)
(Gain) loss on dispositions, net	(39)	(24)
Other, net	(16)	(19)
Changes in certain current assets and liabilities —
-Receivables	(28)	15
-Prepaid income taxes	74	33
-Other current assets	(17)	(3)
-Accounts payable	(12)	(5)
-Accrued taxes	21	66
-Other current liabilities	(25)	(8)
Net cash provided from operating activities	774	1,221
Investing Activities:
Business acquisitions, net of cash acquired	(81)	(50)
Property additions	(135)	(284)
Proceeds from dispositions and asset sales	663	572
Investment in unconsolidated subsidiaries	0	(116)
Payments pursuant to LTSAs	(61)	(85)
Other investing activities	38	(1)
Net cash used for investing activities	424	36
Financing Activities:
Decrease in notes payable, net	(449)	0
Proceeds —
Capital contributions from parent company	0	59
Redemptions and repurchases —
Short-term borrowings	(100)	(100)
Senior notes	(300)	0
Return of capital to parent company	0	(755)
Distributions to noncontrolling interests	(164)	(125)
Capital contributions from noncontrolling interests	173	11
Purchase of membership interests from noncontrolling interests	(60)	0
Payment of common stock dividends	(151)	(154)
Other financing activities	(9)	(6)
Net cash provided from (used for) financing activities	(1,060)	(1,070)
Net Change in Cash, Cash Equivalents, and Restricted Cash	138	187
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	279	181
Cash, Cash Equivalents, and Restricted Cash at End of Period	417	368
Cash paid during the period for —
Interest, net of amounts capitalized	123	133
Income taxes, net	(278)	(612)
Accrued property additions at end of period	44	41
Right-of-use assets obtained under operating leases	30	0
Interest capitalized	10	11
SOUTHERN Co GAS
Operating Activities:
Net income	360	347
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	368	359
Deferred income taxes	(1)	96
Mark-to-market adjustments	104	44
Impairment charges	0	92
Other, net	(20)	(58)
Changes in certain current assets and liabilities —
-Receivables	403	832
-Natural gas for sale	26	49
-Other current assets	(45)	45
-Accounts payable	(75)	(607)
-Accrued taxes	7	(68)
-Accrued compensation	(17)	(34)
-Other current liabilities	12	(48)
Net cash provided from operating activities	1,122	1,049
Investing Activities:
Property additions	(1,045)	(1,008)
Proceeds from dispositions and asset sales	178	32
Cost of removal, net of salvage	(60)	(59)
Change in construction payables, net	25	57
Investment in unconsolidated subsidiaries	(79)	(25)
Other investing activities	8	14
Net cash used for investing activities	(973)	(989)
Financing Activities:
Decrease in notes payable, net	(500)	(383)
Proceeds —
Senior notes	500	0
First mortgage bonds	150	200
Capital contributions from parent company	215	820
Redemptions and repurchases —
First mortgage bonds	0	(50)
Senior notes	0	(300)
Payment of common stock dividends	(399)	(353)
Other financing activities	(3)	(2)
Net cash provided from (used for) financing activities	(37)	(68)
Net Change in Cash, Cash Equivalents, and Restricted Cash	112	(8)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	49	70
Cash, Cash Equivalents, and Restricted Cash at End of Period	161	62
Cash paid during the period for —
Interest, net of amounts capitalized	162	180
Income taxes, net	45	48
Accrued property additions at end of period	146	154
Interest capitalized	$ 5	$ 5

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Interest capitalized	$ 61	$ 55
ALABAMA POWER CO
Interest capitalized	11	15
GEORGIA POWER CO
Interest capitalized	34	25
MISSISSIPPI POWER CO
Interest capitalized	0	1
SOUTHERN POWER CO
Interest capitalized	10	11
SOUTHERN Co GAS
Interest capitalized	$ 5	$ 5

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 3,379	$ 1,975
Receivables —
Customer accounts receivable	1,778	1,614
Energy marketing receivables	328	428
Unbilled revenues	503	599
Other accounts and notes receivable	506	817
Accumulated provision for uncollectible accounts	(99)	(49)
Materials and supplies	1,522	1,388
Fossil fuel for generation	506	521
Natural gas for sale	448	479
Prepaid expenses	299	314
Assets from risk management activities, net of collateral	135	183
Regulatory assets – asset retirement obligations	246	287
Other regulatory assets	813	885
Assets held for sale	0	188
Other current assets	210	188
Total current assets	10,574	9,817
Property, Plant, and Equipment:
In service	108,831	105,114
Less: Accumulated depreciation	32,099	30,765
Plant in service, net of depreciation	76,732	74,349
Nuclear fuel, at amortized cost	804	851
Construction work in progress	8,861	7,880
Total property, plant, and equipment	86,397	83,080
Other Property and Investments:
Goodwill	5,280	5,280
Equity investments in unconsolidated subsidiaries	1,358	1,303
Other intangible assets, net of amortization	499	536
Nuclear decommissioning trusts, at fair value	2,109	2,036
Leveraged leases	653	788
Miscellaneous property and investments	403	391
Total other property and investments	10,302	10,334
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,791	1,800
Deferred charges related to income taxes	799	798
Unamortized loss on reacquired debt	285	300
Regulatory assets – asset retirement obligations, deferred	4,984	4,094
Other regulatory assets, deferred	6,502	6,805
Assets held for sale, deferred	0	601
Other deferred charges and assets	1,524	1,071
Total deferred charges and other assets	15,885	15,469
Total Assets	123,158	118,700
Current Liabilities:
Securities due within one year	4,378	2,989
Notes payable	171	2,055
Energy marketing trade payables	361	442
Accounts payable —
Accounts payable	1,924	2,115
Customer deposits	496	496
Accrued taxes —
Accrued income taxes	75	0
Other accrued taxes	742	659
Accrued interest	421	474
Accrued compensation	843	992
Asset retirement obligations	640	504
Other regulatory liabilities	616	756
Liabilities held for sale	0	5
Operating lease obligations	235	229
Other current liabilities	848	830
Total current liabilities	11,750	12,546
Long-term Debt	45,581	41,798
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	8,342	7,888
Deferred credits related to income taxes	5,763	6,078
Accumulated deferred ITCs	2,251	2,291
Employee benefit obligations	1,753	1,814
Operating lease obligations, deferred	1,570	1,615
Asset retirement obligations, deferred	10,020	9,282
Accrued environmental remediation	220	234
Other cost of removal obligations	2,231	2,239
Other regulatory liabilities, deferred	315	256
Other deferred credits and liabilities	571	609
Total deferred credits and other liabilities	33,036	32,306
Total Liabilities	90,367	86,650
Redeemable Preferred Stock of Subsidiaries	291	291
Common Stockholder's Equity (See accompanying statements)	32,500	31,759
Total Liabilities and Stockholders' Equity	123,158	118,700
ALABAMA POWER CO
Current Assets:
Cash and cash equivalents	1,037	894
Receivables —
Customer accounts receivable	499	425
Unbilled revenues	138	134
Affiliated	37	37
Other accounts and notes receivable	84	72
Accumulated provision for uncollectible accounts	(32)	(22)
Materials and supplies	562	512
Fossil fuel for generation	208	212
Prepaid expenses	71	50
Other regulatory assets	207	242
Other current assets	42	30
Total current assets	2,853	2,586
Property, Plant, and Equipment:
In service	31,355	30,023
Less: Accumulated depreciation	9,920	9,540
Plant in service, net of depreciation	21,435	20,483
Nuclear fuel, at amortized cost	257	296
Construction work in progress	926	890
Total property, plant, and equipment	22,618	21,669
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	63	66
Nuclear decommissioning trusts, at fair value	1,039	1,023
Miscellaneous property and investments	130	128
Total other property and investments	1,232	1,217
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	162	132
Deferred charges related to income taxes	242	244
Deferred under recovered regulatory clause revenues	62	40
Regulatory assets – asset retirement obligations, deferred	1,475	1,019
Other regulatory assets, deferred	1,923	1,976
Other deferred charges and assets	402	269
Total deferred charges and other assets	4,266	3,680
Total Assets	30,969	29,152
Current Liabilities:
Securities due within one year	496	251
Accounts payable —
Affiliated	272	316
Other	353	514
Customer deposits	104	100
Accrued taxes —
Accrued taxes	210	78
Accrued interest	83	92
Accrued compensation	172	216
Asset retirement obligations	251	195
Other regulatory liabilities	144	193
Other current liabilities	116	105
Total current liabilities	2,201	2,060
Long-term Debt	8,622	8,270
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,372	3,260
Deferred credits related to income taxes	1,917	1,960
Accumulated deferred ITCs	96	100
Employee benefit obligations	191	206
Operating lease obligations, deferred	121	107
Asset retirement obligations, deferred	3,707	3,345
Other cost of removal obligations	360	412
Other regulatory liabilities, deferred	137	146
Other deferred credits and liabilities	39	40
Total deferred credits and other liabilities	9,940	9,576
Total Liabilities	20,763	19,906
Redeemable Preferred Stock	291	291
Common Stockholder's Equity (See accompanying statements)	9,915	8,955
Total Liabilities and Stockholders' Equity	30,969	29,152
GEORGIA POWER CO
Current Assets:
Cash and cash equivalents	518	52
Receivables —
Customer accounts receivable	715	533
Unbilled revenues	237	203
Joint owner accounts receivable	120	136
Affiliated	17	21
Other accounts and notes receivable	39	209
Accumulated provision for uncollectible accounts	(29)	(2)
Materials and supplies	572	501
Fossil fuel for generation	269	272
Regulatory assets – storm damage reserves	213	213
Regulatory assets – asset retirement obligations	209	254
Other regulatory assets	251	263
Other current assets	162	140
Total current assets	3,293	2,795
Property, Plant, and Equipment:
In service	39,170	38,137
Less: Accumulated depreciation	12,139	11,753
Plant in service, net of depreciation	27,031	26,384
Nuclear fuel, at amortized cost	547	555
Construction work in progress	6,752	5,650
Total property, plant, and equipment	34,330	32,589
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	50	52
Nuclear decommissioning trusts, at fair value	1,070	1,013
Miscellaneous property and investments	67	64
Total other property and investments	1,187	1,129
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,345	1,428
Deferred charges related to income taxes	522	519
Regulatory assets – asset retirement obligations, deferred	3,307	2,865
Other regulatory assets, deferred	2,521	2,716
Other deferred charges and assets	541	500
Total deferred charges and other assets	8,236	8,028
Total Assets	47,046	44,541
Current Liabilities:
Securities due within one year	531	1,025
Notes payable	0	365
Accounts payable —
Affiliated	561	512
Other	731	711
Customer deposits	280	283
Accrued taxes —
Accrued taxes	415	407
Accrued interest	100	118
Accrued compensation	198	233
Asset retirement obligations	351	265
Other regulatory liabilities	302	447
Operating lease obligations	151	144
Over recovered fuel clause revenues	84	0
Other current liabilities	201	187
Total current liabilities	3,905	4,697
Long-term Debt	12,314	10,791
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,296	3,257
Deferred credits related to income taxes	2,664	2,862
Accumulated deferred ITCs	272	255
Employee benefit obligations	486	540
Operating lease obligations, deferred	1,163	1,282
Asset retirement obligations, deferred	5,901	5,519
Other deferred credits and liabilities	339	273
Total deferred credits and other liabilities	14,121	13,988
Total Liabilities	30,340	29,476
Common Stockholder's Equity (See accompanying statements)	16,706	15,065
Total Liabilities and Stockholders' Equity	47,046	44,541
MISSISSIPPI POWER CO
Current Assets:
Cash and cash equivalents	58	286
Receivables —
Customer accounts receivable	46	35
Unbilled revenues	40	39
Affiliated	14	27
Other accounts and notes receivable	34	26
Materials and supplies	63	61
Fossil fuel for generation	19	26
Other regulatory assets	60	99
Other current assets	19	10
Total current assets	353	609
Property, Plant, and Equipment:
In service	4,966	4,857
Less: Accumulated depreciation	1,553	1,463
Plant in service, net of depreciation	3,413	3,394
Construction work in progress	140	126
Total property, plant, and equipment	3,553	3,520
Other Property and Investments:
Total other property and investments	149	131
Deferred Charges and Other Assets:
Deferred charges related to income taxes	32	32
Regulatory assets – asset retirement obligations, deferred	202	210
Other regulatory assets, deferred	357	360
Accumulated deferred income taxes	130	139
Other deferred charges and assets	72	34
Total deferred charges and other assets	793	775
Total Assets	4,848	5,035
Current Liabilities:
Securities due within one year	0	281
Accounts payable —
Affiliated	54	76
Other	50	75
Accrued taxes —
Accrued taxes	120	105
Accrued interest	14	15
Accrued compensation	28	35
Asset retirement obligations	23	33
Other regulatory liabilities	56	21
Over recovered fuel clause revenues	31	29
Other current liabilities	42	64
Total current liabilities	418	734
Long-term Debt	1,402	1,308
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	422	424
Deferred credits related to income taxes	299	352
Employee benefit obligations	95	99
Asset retirement obligations, deferred	158	157
Other cost of removal obligations	195	189
Other regulatory liabilities, deferred	64	76
Other deferred credits and liabilities	35	44
Total deferred credits and other liabilities	1,268	1,341
Total Liabilities	3,088	3,383
Common Stockholder's Equity (See accompanying statements)	1,760	1,652
Total Liabilities and Stockholders' Equity	4,848	5,035
SOUTHERN POWER CO
Current Assets:
Cash and cash equivalents	416	279
Receivables —
Customer accounts receivable	135	107
Affiliated	41	30
Other accounts and notes receivable	37	73
Materials and supplies	204	191
Prepaid income taxes	33	36
Other current assets	37	43
Total current assets	903	759
Property, Plant, and Equipment:
In service	13,600	13,270
Less: Accumulated depreciation	2,776	2,464
Plant in service, net of depreciation	10,824	10,806
Construction work in progress	335	515
Total property, plant, and equipment	11,159	11,321
Other Property and Investments:
Intangible assets, net of amortization	307	322
Equity investments in unconsolidated subsidiaries	19	28
Miscellaneous property and investments	19	28
Total other property and investments	326	350
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	395	369
Prepaid LTSAs	160	128
Assets held for sale, deferred	0	601
Accumulated deferred income taxes	231	551
Income taxes receivable, non-current	13	5
Other deferred charges and assets	237	216
Total deferred charges and other assets	1,036	1,870
Total Assets	13,424	14,300
Current Liabilities:
Securities due within one year	525	824
Notes payable	0	549
Accounts payable —
Affiliated	49	56
Other	69	85
Accrued taxes —
Accrued income taxes	9	0
Other accrued taxes	31	26
Accrued interest	26	32
Other current liabilities	104	132
Total current liabilities	813	1,704
Long-term Debt	3,630	3,574
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	117	115
Accumulated deferred ITCs	1,687	1,731
Operating lease obligations, deferred	404	376
Other deferred credits and liabilities	162	178
Total deferred credits and other liabilities	2,370	2,400
Total Liabilities	6,813	7,678
Common Stockholder's Equity (See accompanying statements)	6,611	6,622
Total Liabilities and Stockholders' Equity	13,424	14,300
SOUTHERN Co GAS
Current Assets:
Cash and cash equivalents	157	46
Receivables —
Customer accounts receivable	214	323
Energy marketing receivables	328	428
Unbilled revenues	60	183
Affiliated	3	5
Other accounts and notes receivable	42	114
Accumulated provision for uncollectible accounts	(34)	(18)
Natural gas for sale	448	479
Prepaid expenses	92	65
Assets from risk management activities, net of collateral	75	177
Other regulatory assets	110	92
Assets held for sale	0	171
Other current assets	43	41
Total current assets	1,538	2,106
Property, Plant, and Equipment:
In service	17,202	16,344
Less: Accumulated depreciation	4,761	4,650
Plant in service, net of depreciation	12,441	11,694
Construction work in progress	655	613
Total property, plant, and equipment	13,096	12,307
Other Property and Investments:
Goodwill	5,015	5,015
Equity investments in unconsolidated subsidiaries	1,301	1,251
Other intangible assets, net of amortization	55	70
Miscellaneous property and investments	20	20
Total other property and investments	6,391	6,356
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	85	93
Other regulatory assets, deferred	580	618
Other deferred charges and assets	242	207
Total deferred charges and other assets	907	918
Total Assets	21,932	21,687
Current Liabilities:
Securities due within one year	334	0
Notes payable	150	650
Energy marketing trade payables	361	442
Accounts payable —
Affiliated	46	41
Other	341	315
Customer deposits	94	96
Accrued taxes —
Accrued taxes	78	71
Accrued interest	66	52
Accrued compensation	83	100
Liabilities from risk management activities, net of collateral	31	21
Other regulatory liabilities	112	94
Other current liabilities	128	128
Total current liabilities	1,824	2,010
Long-term Debt	6,127	5,845
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	1,213	1,219
Deferred credits related to income taxes	854	874
Employee benefit obligations	247	265
Operating lease obligations, deferred	70	78
Accrued environmental remediation	220	233
Other cost of removal obligations	1,642	1,606
Other deferred credits and liabilities	50	51
Total deferred credits and other liabilities	4,296	4,326
Total Liabilities	12,247	12,181
Common Stockholder's Equity (See accompanying statements)	9,685	9,506
Total Liabilities and Stockholders' Equity	$ 21,932	$ 21,687

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other intangible assets, amortization	$ 316	$ 280
SOUTHERN POWER CO
Other intangible assets, amortization	84	69
SOUTHERN Co GAS
Other intangible assets, amortization	$ 191	$ 176

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Treasury	Paid-In Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	ALABAMA POWER CO	ALABAMA POWER COCommon Stock	ALABAMA POWER COPaid-In Capital	ALABAMA POWER CORetained Earnings (Accumulated Deficit)	ALABAMA POWER COAccumulated Other Comprehensive Income (Loss)	GEORGIA POWER CO	GEORGIA POWER COCommon Stock	GEORGIA POWER COPaid-In Capital	GEORGIA POWER CORetained Earnings (Accumulated Deficit)	GEORGIA POWER COAccumulated Other Comprehensive Income (Loss)	MISSISSIPPI POWER CO	MISSISSIPPI POWER COCommon Stock	MISSISSIPPI POWER COPaid-In Capital	MISSISSIPPI POWER CORetained Earnings (Accumulated Deficit)	MISSISSIPPI POWER COAccumulated Other Comprehensive Income (Loss)	SOUTHERN POWER CO	SOUTHERN POWER COTotal Common Stockholders' Equity	SOUTHERN POWER COPaid-In Capital	SOUTHERN POWER CORetained Earnings (Accumulated Deficit)	SOUTHERN POWER COAccumulated Other Comprehensive Income (Loss)	SOUTHERN POWER CONoncontrolling Interests	SOUTHERN Co GAS	SOUTHERN Co GASPaid-In Capital	SOUTHERN Co GASRetained Earnings (Accumulated Deficit)	SOUTHERN Co GASAccumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018		1,035	1						31					9					1
Beginning balance at Dec. 31, 2018	$ 29,039	$ 5,164	$ (38)	$ 11,094	$ 8,706	$ (203)	$ 4,316	$ 7,477	$ 1,222	$ 3,508	$ 2,775	$ (28)	$ 14,323	$ 398	$ 10,322	$ 3,612	$ (9)	$ 1,609	$ 38	$ 4,546	$ (2,971)	$ (4)	$ 7,284	$ 2,968	$ 1,600	$ 1,352	$ 16	$ 4,316	$ 8,570	$ 8,856	$ (312)	$ 26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,055				2,084		(29)
Net income (loss)													311			311		37			37		27	56		56		(29)	270		270
Net income								217			217
Return of capital to parent company																		(38)		(38)
Capital contributions from parent company								1,236		1,236			29		29			2		2			1	1	1				17	17
Other comprehensive income (loss)								1				1	1				1						(4)	(4)			(4)		(1)			(1)
Stock issued (in shares)		6
Stock issued	224	$ 28		196
Stock-based compensation	24			24
Cash dividends on common stock	(623)				(623)			(211)			(211)		(394)			(394)							(51)	(51)		(51)			(118)		(118)
Contributions from noncontrolling interests	3						3																3					3
Distributions to noncontrolling interests	(41)						(41)																(41)					(41)
Other	6		$ (2)	7			1						(1)		(1)								(1)	(2)	(1)	(1)		1
Ending balance (in shares) at Mar. 31, 2019		1,041	1						31					9					1
Ending balance at Mar. 31, 2019	30,687	$ 5,192	$ (40)	11,321	10,167	(203)	4,250	8,720	$ 1,222	4,744	2,781	(27)	14,269	$ 398	10,350	3,529	(8)	1,610	$ 38	4,510	(2,934)	(4)	7,218	2,968	1,600	1,356	12	4,250	8,738	8,873	(160)	25
Beginning balance (in shares) at Dec. 31, 2018		1,035	1						31					9					1
Beginning balance at Dec. 31, 2018	29,039	$ 5,164	$ (38)	11,094	8,706	(203)	4,316	7,477	$ 1,222	3,508	2,775	(28)	14,323	$ 398	10,322	3,612	(9)	1,609	$ 38	4,546	(2,971)	(4)	7,284	2,968	1,600	1,352	16	4,316	8,570	8,856	(312)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	4,335							993					1,598					139					342						347
Net income	4,298							982															316						347
Purchase of membership interests from noncontrolling interests	0																						0
Ending balance (in shares) at Sep. 30, 2019		1,050	1						31					9					1
Ending balance at Sep. 30, 2019	31,791	$ 5,234	$ (41)	11,512	11,087	(279)	4,278	9,086	$ 1,222	4,765	3,124	(25)	14,764	$ 398	10,408	4,028	(70)	1,639	$ 38	4,437	(2,832)	(4)	6,693	2,415	905	1,514	(4)	4,278	9,393	9,692	(318)	19
Beginning balance (in shares) at Mar. 31, 2019		1,041	1						31					9					1
Beginning balance at Mar. 31, 2019	30,687	$ 5,192	$ (40)	11,321	10,167	(203)	4,250	8,720	$ 1,222	4,744	2,781	(27)	14,269	$ 398	10,350	3,529	(8)	1,610	$ 38	4,510	(2,934)	(4)	7,218	2,968	1,600	1,356	12	4,250	8,738	8,873	(160)	25
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	928				899		29
Net income (loss)													448			448		37			37		203	174		174		29	106		106
Net income								296			296
Return of capital to parent company																		(38)		(38)			(505)	(505)	(505)
Capital contributions from parent company								23		23			20		20			8		8			7	7	7				35	35
Other comprehensive income (loss)	(35)					(35)		1				1	(27)				(27)						(8)	(8)			(8)		(3)			(3)
Stock issued (in shares)		5
Stock issued	228	$ 25		203
Stock-based compensation	11			11
Cash dividends on common stock	(646)				(646)			(211)			(211)		(394)			(394)							(52)	(52)		(52)			(117)		(117)
Contributions from noncontrolling interests	2						2																2					2
Distributions to noncontrolling interests	(47)						(47)																(47)					(47)
Other	3		$ (1)	5			(1)						0		1	(1)							0	1		1		(1)
Ending balance (in shares) at Jun. 30, 2019		1,046	1						31					9					1
Ending balance at Jun. 30, 2019	31,131	$ 5,217	$ (41)	11,540	10,420	(238)	4,233	8,829	$ 1,222	4,767	2,866	(26)	14,316	$ 398	10,371	3,582	(35)	1,617	$ 38	4,480	(2,897)	(4)	6,818	2,585	1,102	1,479	4	4,233	8,759	8,908	(171)	22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,341				1,316		25
Net income (loss)	1,345							473					839			839		65			65		111	86		86		25	(29)		(29)
Net income	1,316							469			469												86						(29)
Return of capital to parent company								(2)		(2)								(43)		(43)			(250)	(250)	(250)
Capital contributions from parent company													38		38								53	53	53				784	784
Other comprehensive income (loss)	(41)					(41)		1				1	(35)				(35)						(8)	(8)			(8)		(3)			(3)
Issuance of equity units	(198)			(198)
Stock issued (in shares)		4
Stock issued	171	$ 17		154
Stock-based compensation	12			12
Cash dividends on common stock	(649)				(649)			(211)			(211)		(394)			(394)							(51)	(51)		(51)			(118)		(118)
Contributions from noncontrolling interests	63						63																63					63
Distributions to noncontrolling interests	(43)						(43)																(43)					(43)
Other	4		$ 0	4			0						0		(1)	1
Ending balance (in shares) at Sep. 30, 2019		1,050	1						31					9					1
Ending balance at Sep. 30, 2019	31,791	$ 5,234	$ (41)	11,512	11,087	(279)	4,278	9,086	$ 1,222	4,765	3,124	(25)	14,764	$ 398	10,408	4,028	(70)	1,639	$ 38	4,437	(2,832)	(4)	6,693	2,415	905	1,514	(4)	4,278	9,393	9,692	(318)	19
Beginning balance (in shares) at Dec. 31, 2019		1,054	1						31					9					1
Beginning balance at Dec. 31, 2019	31,759	$ 5,257	$ (42)	11,734	10,877	(321)	4,254	8,955	$ 1,222	4,755	3,001	(23)	15,065	$ 398	10,962	3,756	(51)	1,652	$ 38	4,449	(2,832)	(3)	6,622	2,368	909	1,485	(26)	4,254	9,506	9,697	(198)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	837				868		(31)
Net income (loss)													331			331		32			32		44	75		75		(31)	275		275
Net income								280			280
Return of capital to parent company																		(37)		(37)									(2)	(2)
Capital contributions from parent company								612		612			502		502			76		76
Other comprehensive income (loss)	(47)					(47)		1				1	(1)				(1)						(33)	(33)			(33)		(15)			(15)
Stock issued (in shares)		3
Stock issued	52	$ 9		43
Stock-based compensation	5			5
Cash dividends on common stock	(655)				(655)			(239)			(239)		(385)			(385)							(50)	(50)		(50)			(133)		(133)
Contributions from noncontrolling interests	16						16																16					16
Distributions to noncontrolling interests	(48)						(48)																(48)					(48)
Other	(3)		$ (2)		(2)	1												(1)		(1)
Ending balance (in shares) at Mar. 31, 2020		1,057	1						31					9					1
Ending balance at Mar. 31, 2020	31,916	$ 5,266	$ (44)	11,782	11,088	(367)	4,191	9,609	$ 1,222	5,367	3,042	(22)	15,512	$ 398	11,464	3,702	(52)	1,722	$ 38	4,487	(2,800)	(3)	6,551	2,360	909	1,510	(59)	4,191	9,631	9,695	(56)	(8)
Beginning balance (in shares) at Dec. 31, 2019		1,054	1						31					9					1
Beginning balance at Dec. 31, 2019	31,759	$ 5,257	$ (42)	11,734	10,877	(321)	4,254	8,955	$ 1,222	4,755	3,001	(23)	15,065	$ 398	10,962	3,756	(51)	1,652	$ 38	4,449	(2,832)	(3)	6,622	2,368	909	1,485	(26)	4,254	9,506	9,697	(198)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,746							1,033					1,411					138					215						360
Net income	2,732							1,022															212						360
Purchase of membership interests from noncontrolling interests	60																						60
Ending balance (in shares) at Sep. 30, 2020		1,057	1						31					9					1
Ending balance at Sep. 30, 2020	32,500	$ 5,267	$ (44)	11,810	11,600	(344)	4,211	9,915	$ 1,222	5,408	3,305	(20)	16,706	$ 398	12,345	4,011	(48)	1,760	$ 38	4,456	(2,731)	(3)	6,611	2,400	908	1,546	(54)	4,211	9,685	9,925	(237)	(3)
Beginning balance (in shares) at Mar. 31, 2020		1,057	1						31					9					1
Beginning balance at Mar. 31, 2020	31,916	$ 5,266	$ (44)	11,782	11,088	(367)	4,191	9,609	$ 1,222	5,367	3,042	(22)	15,512	$ 398	11,464	3,702	(52)	1,722	$ 38	4,487	(2,800)	(3)	6,551	2,360	909	1,510	(59)	4,191	9,631	9,695	(56)	(8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	617				612		5
Net income (loss)													308			308		39			39		68	63		63		5	71		71
Net income								298			298
Return of capital to parent company																		(37)		(37)
Capital contributions from parent company								1		1			1		1														200	200
Other comprehensive income (loss)	4					4		1				1	2				2						(3)	(3)			(3)
Stock issued	7			7
Stock-based compensation	11			11
Cash dividends on common stock	(677)				(677)			(239)			(239)		(386)			(386)							(50)	(50)		(50)			(133)		(133)
Contributions from noncontrolling interests	165						165																165					165
Distributions to noncontrolling interests	(70)						(70)																(70)					(70)
Other	(12)			(13)	1																		(2)	(2)	(2)	0	0	0
Ending balance (in shares) at Jun. 30, 2020		1,057	1						31					9					1
Ending balance at Jun. 30, 2020	31,961	$ 5,266	$ (44)	11,787	11,024	(363)	4,291	9,670	$ 1,222	5,368	3,101	(21)	15,437	$ 398	11,465	3,624	(50)	1,724	$ 38	4,450	(2,761)	(3)	6,659	2,368	907	1,523	(62)	4,291	9,769	9,895	(118)	(8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,279				1,251		28
Net income (loss)	1,283							448					773			773		67			67		102	74		74		28	14		14
Net income	1,251							444			444												74						14
Return of capital to parent company																							(4)	(4)	(4)
Capital contributions from parent company								40		40			880		880			6		6									30	30
Other comprehensive income (loss)	20					20		1				1	2				2						8	8			8		5			5
Stock issued	4	1		3
Stock-based compensation	15			15
Cash dividends on common stock	(676)				(676)			(240)			(240)		(386)			(386)		(37)			(37)		(51)	(51)		(51)			(133)		(133)
Contributions from noncontrolling interests	2						2																2					2
Distributions to noncontrolling interests	(51)						(51)																(51)					(51)
Purchase of membership interests from noncontrolling interests	(55)			5			(60)																(55)	5	5			(60)
Other	1	$ 0	$ 0	0	1	(1)	1																1	0	0	0		1
Ending balance (in shares) at Sep. 30, 2020		1,057	1						31					9					1
Ending balance at Sep. 30, 2020	$ 32,500	$ 5,267	$ (44)	$ 11,810	$ 11,600	$ (344)	$ 4,211	$ 9,915	$ 1,222	$ 5,408	$ 3,305	$ (20)	$ 16,706	$ 398	$ 12,345	$ 4,011	$ (48)	$ 1,760	$ 38	$ 4,456	$ (2,731)	$ (3)	$ 6,611	$ 2,400	$ 908	$ 1,546	$ (54)	$ 4,211	$ 9,685	$ 9,925	$ (237)	$ (3)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Cash dividends (in dollars per share)	$ 0.64	$ 0.64	$ 0.62	$ 0.62	$ 0.62	$ 0.60

INTRODUCTION

INTRODUCTION	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
INTRODUCTION	INTRODUCTION The condensed quarterly financial statements of each Registrant included herein have been prepared by such Registrant, without audit, pursuant to the rules and regulations of the SEC. The Condensed Balance Sheets as of December 31, 2019 have been derived from the audited financial statements of each Registrant. In the opinion of each Registrant's management, the information regarding such Registrant furnished herein reflects all adjustments, which, except as otherwise disclosed, are of a normal recurring nature, necessary to present fairly the results of operations for the periods ended September 30, 2020 and 2019. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations, although each Registrant believes that the disclosures regarding such Registrant are adequate to make the information presented not misleading. Disclosures which would substantially duplicate the disclosures in the Form 10-K and details which have not changed significantly in amount or composition since the filing of the Form 10-K are generally omitted from this Quarterly Report on Form 10-Q unless specifically required by GAAP. Therefore, these Condensed Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K. Due to the seasonal variations in the demand for energy and other factors, including the impacts of the COVID-19 pandemic, operating results for the periods presented are not necessarily indicative of the operating results to be expected for the full year. Certain prior year data presented in the financial statements have been reclassified to conform to the current year presentation. These reclassifications had no impact on the overall results of operations, financial position, or cash flows of any Registrant. Goodwill and Other Intangible Assets Goodwill at September 30, 2020 and December 31, 2019 was as follows: Goodwill (in millions) Southern Company $ 5,280 Southern Company Gas: Gas distribution operations $ 4,034 Gas marketing services 981 Southern Company Gas total $ 5,015 Goodwill is not amortized but is subject to an annual impairment test in the fourth quarter of the year and on an interim basis as events and changes in circumstances occur, including, but not limited to, a significant change in operating performance, the business climate, legal or regulatory factors, or a planned sale or disposition of a significant portion of the business. The continued COVID-19 pandemic and related responses continue to disrupt supply chains, reduce labor availability and productivity, and reduce economic activity. These effects could have a variety of adverse impacts on Southern Company and its subsidiaries, including the $263 million of goodwill recorded at PowerSecure. If the impact of the COVID-19 pandemic becomes significant to the operating results of PowerSecure and its businesses, a portion of the associated goodwill may become impaired. The ultimate outcome of this matter cannot be determined at this time. Other intangible assets were as follows: At September 30, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (130) $ 82 $ 212 $ (116) $ 96 Trade names 64 (30) 34 64 (25) 39 Storage and transportation contracts 64 (64) — 64 (62) 2 PPA fair value adjustments 390 (84) 306 390 (69) 321 Other 10 (8) 2 11 (8) 3 Total other intangible assets subject to amortization $ 740 $ (316) $ 424 $ 741 $ (280) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (316) $ 499 $ 816 $ (280) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (84) $ 306 $ 390 $ (69) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (115) $ 41 $ 156 $ (104) $ 52 Trade names 26 (12) 14 26 (10) 16 Wholesale gas services Storage and transportation contracts 64 (64) — 64 (62) 2 Total other intangible assets subject to amortization $ 246 $ (191) $ 55 $ 246 $ (176) $ 70 Amortization associated with other intangible assets was as follows: Three Months Ended Nine Months Ended September 30, 2020 (in millions) Southern Company (a) $ 12 $ 37 Southern Power (b) $ 5 $ 15 Southern Company Gas Gas marketing services $ 4 $ 13 Wholesale gas services (b) 1 2 Southern Company Gas total $ 5 $ 15 (a) Includes $6 million and $17 million for the three and nine months ended September 30, 2020, respectively, recorded as a reduction to operating revenues. (b) Recorded as a reduction to operating revenues. Restricted Cash The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the Registrants that had restricted cash at September 30, 2020 and/or December 31, 2019: Southern Southern Power Southern At September At December 31, 2019 At September 30, 2020 At September At December 31, 2019 (in millions) (in millions) (in millions) Cash and cash equivalents $ 3,379 $ 1,975 $ 416 $ 157 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — — 3 Other current assets 4 — — 4 — Other deferred charges and assets 1 — 1 — — Total cash, cash equivalents, and restricted cash $ 3,383 (b) $ 1,978 $ 417 $ 161 $ 49 (a) For Southern Company Gas, reflects restricted cash held as collateral for workers' compensation, life insurance, and long-term disability insurance. For Southern Power, reflects restricted cash held for construction payables. (b) Total does not add due to rounding. Natural Gas for Sale Southern Company Gas, with the exception of Nicor Gas, carries natural gas inventory on a WACOG basis. For any declines in market prices below the WACOG considered to be other than temporary, an adjustment is recorded to reduce the value of natural gas inventories to market value. Nicor Gas' natural gas inventory is carried at cost on a LIFO basis. Inventory decrements occurring during the year that are restored prior to year end are charged to cost of natural gas at the estimated annual replacement cost. Inventory decrements that are not restored prior to year end are charged to cost of natural gas at the actual LIFO cost of the inventory layers liquidated. Southern Company Gas recorded no material adjustments to natural gas inventories for the three and nine months ended September 30, 2020 or the three months ended September 30, 2019 and recorded an adjustment of $10 million for the nine months ended September 30, 2019. Nicor Gas' inventory decrement at September 30, 2020 is expected to be restored prior to year end. Asset Retirement Obligations See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. Details of changes in AROs for Southern Company, Alabama Power, and Georgia Power during the first nine months of 2020 are shown in the following table. There were no material changes in AROs for the other Registrants during the first nine months of 2020. Southern Company Alabama Power Georgia Power (in millions) Balance at December 31, 2019 $ 9,786 $ 3,540 $ 5,784 Liabilities incurred 15 — 10 Liabilities settled (315) (157) (130) Accretion 308 113 177 Cash flow revisions 866 462 411 Balance at September 30, 2020 $ 10,660 $ 3,958 $ 6,252 In June 2020, Alabama Power recorded an increase of approximately $462 million to its AROs related to the CCR Rule and the related state rule primarily due to management's completion of a feasibility study and the related cost estimates during the second quarter 2020 for one of its ash ponds. Alabama Power's increase also reflects costs associated with the addition of a water treatment system to the design of another ash pond. The additional estimated costs to close these ash ponds under the planned closure-in-place methodology primarily relate to inputs from contractor bids, design revisions, and changes in the expected volume of ash handling. During the third quarter 2020, Georgia Power completed an assessment of its plans to close the ash ponds at all of its generating plants in compliance with the CCR Rule and the related state rule. The related cost estimates were further refined, including updates to long-term post-closure care requirements, market pricing, and timing of future cash outlays. As a result, in September 2020, Georgia Power recorded an increase of approximately $411 million to its AROs related to the CCR Rule and the related state rule. The traditional electric operating companies expect to continue updating their cost estimates and ARO liabilities periodically as additional information related to ash pond closure methodologies, schedules, and/or costs becomes available, and the changes could be material. Additionally, the closure designs and plans in the States of Alabama and Georgia are subject to approval by environmental regulatory agencies. Absent continued recovery of ARO costs through regulated rates, results of operations, cash flows, and financial condition for Southern Company and the traditional electric operating companies could be materially impacted. See Note (B) and Note 2 to the financial statements in Item 8 of the Form 10-K under "Georgia Power – Integrated Resource Plan" for additional information. The ultimate outcome of these matters cannot be determined at this time. Depreciation and Amortization See Note 5 to the financial statements under "Depreciation and Amortization – Southern Power" in Item 8 of the Form 10-K for additional information. Effective January 1, 2020, Southern Power revised the depreciable lives of its natural gas generating facilities from up to 45 years to up to 50 years. This revision resulted in an immaterial decrease in depreciation for the three and nine months ended September 30, 2020 and is expected to result in an immaterial decrease in annual depreciation for 2020.

REGULATORY MATTERS

REGULATORY MATTERS	9 Months Ended
	Sep. 30, 2020
Regulated Operations [Abstract]
REGULATORY MATTERS	REGULATORY MATTERS See Note 2 to the financial statements in Item 8 of the Form 10-K for additional information relating to regulatory matters. The recovery balances for certain retail regulatory clauses of the traditional electric operating companies and Southern Company Gas at September 30, 2020 and December 31, 2019 were as follows: Regulatory Clause Balance Sheet Line Item September 30, December 31, 2019 (in millions) Alabama Power Rate CNP Compliance Other regulatory liabilities, current $ 12 $ 55 Other regulatory liabilities, deferred 38 7 Rate CNP PPA Deferred under recovered regulatory clause revenues 62 40 Retail Energy Cost Recovery Other regulatory liabilities, current 107 32 Other regulatory liabilities, deferred 16 17 Natural Disaster Reserve Other regulatory liabilities, current 7 37 Other regulatory liabilities, deferred 51 113 Georgia Power Fuel Cost Recovery Over recovered fuel clause revenues $ 84 $ — Other deferred credits and liabilities 67 73 Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 23 $ 23 Ad Valorem Tax Other regulatory assets 11 47 Other regulatory assets, deferred 36 — Property Damage Reserve Other regulatory liabilities, deferred 48 54 Southern Company Gas Natural Gas Cost Recovery Other regulatory liabilities $ 84 $ 74 Alabama Power Petition for Certificate of Convenience and Necessity On August 14, 2020, the Alabama PSC issued its order regarding Alabama Power's petition for a certificate of convenience and necessity (CCN), which authorized Alabama Power to (i) construct an approximately 720-MW combined cycle facility at Alabama Power's Plant Barry (Plant Barry Unit 8), which is expected to be placed in service by the end of 2023, (ii) complete the Autauga Combined Cycle Acquisition, which occurred on August 31, 2020, (iii) purchase approximately 240 MWs of combined cycle generation under a long-term PPA, which began on September 1, 2020, and (iv) pursue up to approximately 200 MWs of cost-effective demand-side management and distributed energy resource programs. The Alabama PSC authorized the recovery of actual costs for the construction of Plant Barry Unit 8 up to 5% above the estimated in-service cost of $652 million. In so doing, it recognized the potential for developments that could cause the project costs to exceed the capped amount, in which case Alabama Power would provide documentation to the Alabama PSC to explain and justify potential recovery of the additional costs. The Alabama PSC further directed that the proposed solar generation of approximately 400 MWs, coupled with battery energy storage systems (solar/battery systems), be evaluated under an existing Renewable Generation Certificate (RGC) issued by the Alabama PSC in September 2015. The contracts proposed in the CCN petition expired on July 31, 2020. Any future requests for solar/battery systems will be evaluated under the RGC process. Energy Alabama, Gasp, Inc., and the Sierra Club filed petitions for reconsideration and rehearing with the Alabama PSC. Alabama PSC action on these petitions is expected by November 10, 2020. Upon issuance of a written order reflecting such action, affected parties would have 30 days to pursue an appeal through the State of Alabama court system. Alabama Power expects to recover all approved costs associated with the CCN through existing rate mechanisms as outlined in Note 2 to the financial statements in Item 8 of the Form 10-K. The ultimate outcome of these matters cannot be determined at this time. Rate ECR On August 7, 2020, the Alabama PSC issued an order authorizing Alabama Power to reduce its over-collected fuel balance by $100 million and return that amount to customers in the form of bill credits for the billing month of October 2020. Any portion of the $100 million undistributed following the bill credit process will remain in the Rate ECR regulatory liability for the benefit of customers. Rate NDR In the third quarter 2020, Alabama Power recorded $44 million against the NDR for damages incurred to its transmission and distribution facilities from Hurricane Sally. The NDR balance available for storm damages was $51 million as of September 30, 2020. If the balance falls below $50 million, a reserve establishment charge would be activated (and the ongoing reserve maintenance charge concurrently suspended) until the reserve balance reaches $75 million. Georgia Power Rate Plans 2019 ARP In accordance with the terms of the 2019 ARP, on October 1, 2020, Georgia Power filed the following tariff adjustments to become effective January 1, 2021 pending approval by the Georgia PSC: • increase traditional base tariffs by approximately $120 million; • increase the Environmental Compliance Cost Recovery tariff by approximately $2 million; • decrease Demand-Side Management tariffs by approximately $15 million; and • increase Municipal Franchise Fee tariffs by approximately $4 million. The ultimate outcome of this matter cannot be determined at this time. 2013 ARP In 2019, Georgia Power's retail ROE exceeded 12.00% and, under the modified sharing mechanism pursuant to the 2019 ARP, Georgia Power reduced regulatory assets by approximately $60 million and accrued refunds for retail customers of approximately $60 million. On September 1, 2020, the Georgia PSC authorized Georgia Power to issue customers bill credits prior to final review of the 2019 Annual Surveillance Report by the staff of the Georgia PSC. Georgia Power issued the bill credits in October 2020. Deferral of Incremental COVID-19 Costs On April 7, 2020 and June 2, 2020, in response to the COVID-19 pandemic, the Georgia PSC approved orders directing Georgia Power to continue its previous, voluntary suspension of customer disconnections through July 14, 2020 and to defer the resulting incremental bad debt as a regulatory asset. On June 16, 2020 and July 7, 2020, the Georgia PSC approved orders establishing a methodology for identifying incremental bad debt and allowing the deferral of other incremental costs associated with the COVID-19 pandemic. The period over which such costs will be recovered is expected to be determined in Georgia Power's next base rate case. At September 30, 2020, the incremental costs deferred totaled approximately $38 million. The ultimate outcome of this matter cannot be determined at this time. Integrated Resource Plan On March 5, 2020, the Sierra Club filed a petition for judicial review in the Superior Court of Fulton County to appeal the Georgia PSC's decision in the 2019 ARP allowing Georgia Power to recover compliance costs for CCR AROs. Georgia Power intervened in the appeal on June 22, 2020. The ultimate outcome of this matter cannot be determined at this time. Fuel Cost Recovery On May 28, 2020, the Georgia PSC approved a stipulation agreement among Georgia Power, the staff of the Georgia PSC, and certain intervenors to lower total fuel billings by approximately $740 million over a two-year period effective June 1, 2020. In addition, Georgia Power further lowered fuel billings by approximately $44 million under an interim fuel rider effective June 1, 2020 through September 30, 2020. Georgia Power continues to be allowed to adjust its fuel cost recovery rates under an interim fuel rider prior to its next fuel case if the under or over recovered fuel balance exceeds $200 million. Georgia Power is scheduled to file its next fuel case no later than February 28, 2023. Nuclear Construction In 2009, the Georgia PSC certified construction of Plant Vogtle Units 3 and 4, in which Georgia Power holds a 45.7% ownership interest. In 2012, the NRC issued the related combined construction and operating licenses, which allowed full construction of the two AP1000 nuclear units (with electric generating capacity of approximately 1,100 MWs each) and related facilities to begin. Until March 2017, construction on Plant Vogtle Units 3 and 4 continued under the Vogtle 3 and 4 Agreement, which was a substantially fixed price agreement. In March 2017, the EPC Contractor filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy Code. In connection with the EPC Contractor's bankruptcy filing, Georgia Power, acting for itself and as agent for the other Vogtle Owners, entered into several transitional arrangements to allow construction to continue. In July 2017, Georgia Power, acting for itself and as agent for the other Vogtle Owners, entered into the Vogtle Services Agreement, whereby Westinghouse provides facility design and engineering services, procurement and technical support, and staff augmentation on a time and materials cost basis. The Vogtle Services Agreement provides that it will continue until the start-up and testing of Plant Vogtle Units 3 and 4 are complete and electricity is generated and sold from both units. The Vogtle Services Agreement is terminable by the Vogtle Owners upon 30 days' written notice. In October 2017, Georgia Power, acting for itself and as agent for the other Vogtle Owners, executed the Bechtel Agreement, a cost reimbursable plus fee arrangement, whereby Bechtel is reimbursed for actual costs plus a base fee and an at-risk fee, which is subject to adjustment based on Bechtel's performance against cost and schedule targets. Each Vogtle Owner is severally (not jointly) liable for its proportionate share, based on its ownership interest, of all amounts owed to Bechtel under the Bechtel Agreement. The Vogtle Owners may terminate the Bechtel Agreement at any time for their convenience, provided that the Vogtle Owners will be required to pay amounts related to work performed prior to the termination (including the applicable portion of the base fee), certain termination-related costs, and, at certain stages of the work, the applicable portion of the at-risk fee. Bechtel may terminate the Bechtel Agreement under certain circumstances, including certain Vogtle Owner suspensions of work, certain breaches of the Bechtel Agreement by the Vogtle Owners, Vogtle Owner insolvency, and certain other events. See Note 8 to the financial statements under "Long-term Debt – DOE Loan Guarantee Borrowings" in Item 8 of the Form 10-K for information on the Amended and Restated Loan Guarantee Agreement, including applicable covenants, events of default, mandatory prepayment events, and conditions to borrowing. Cost and Schedule Georgia Power's approximate proportionate share of the remaining estimated capital cost to complete Plant Vogtle Units 3 and 4 by the expected in-service dates of November 2021 and November 2022, respectively, is as follows: (in billions) Base project capital cost forecast (a)(b) $ 8.4 Construction contingency estimate 0.1 Total project capital cost forecast (a)(b) 8.5 Net investment as of September 30, 2020 (b) (6.9) Remaining estimate to complete (a) $ 1.6 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $240 million, of which $71 million had been accrued through September 30, 2020. (b) Net of $1.7 billion received from Toshiba under the Guarantee Settlement Agreement and approximately $188 million in related customer refunds. Georgia Power estimates that its financing costs for construction of Plant Vogtle Units 3 and 4 will total approximately $3.0 billion, of which $2.5 billion had been incurred through September 30, 2020. As part of its ongoing processes, Southern Nuclear continues to evaluate cost and schedule forecasts on a regular basis to incorporate current information available, particularly in the areas of engineering support, commodity installation, system turnovers and related test results, and workforce statistics. As of June 30, 2020, assignments of contingency exceeded the remaining balance of the $366 million construction contingency originally established in the second quarter 2018 by approximately $34 million. This contingency was used to address cost risks related to construction productivity, including the April 2020 reduction in workforce designed to mitigate impacts of the COVID-19 pandemic described below; craft labor incentives; adding resources for supervision, field support, project management, initial test program, start-up, and operations and engineering support; subcontracts; and procurement, among other factors. As a result of these factors, Georgia Power established $115 million of additional construction contingency as of June 30, 2020 for further potential risks including, among other factors, construction productivity and expected impacts of the COVID-19 pandemic; additional resources for supervision, field support, project management, initial test program, start-up, and operations and engineering support; subcontracts; and procurement. After considering the significant level of uncertainty that exists regarding the future recoverability of these costs since the ultimate outcome of these matters is subject to the outcome of future assessments by management, as well as Georgia PSC decisions in future regulatory proceedings, Georgia Power recorded a total pre-tax charge to income of $149 million ($111 million after tax) for the increase in the total project capital cost forecast as of June 30, 2020. As and when these amounts are spent, Georgia Power may request the Georgia PSC to evaluate those expenditures for rate recovery. During the third quarter 2020, approximately $5 million of the construction contingency established in the second quarter 2020 was assigned to the base capital cost forecast for cost risks primarily associated with construction productivity and field support. In April 2019, Southern Nuclear established aggressive target values for monthly construction production and system turnover activities as part of a strategy to maintain and, where possible, build margin to the regulatory-approved in-service dates of November 2021 for Unit 3 and November 2022 for Unit 4. Through early 2020, the project faced challenges with the April 2019 aggressive strategy targets including, but not limited to, electrical and pipefitting labor productivity and work package closure rates, which resulted in a backlog of activities and completion percentages below the April 2019 aggressive strategy targets. In February 2020, Southern Nuclear updated its cost and schedule forecast, which, at that time, did not change the total project capital cost forecast and confirmed the expected in-service dates of November 2021 for Unit 3 and November 2022 for Unit 4. This update included initiatives to improve productivity while refining and extending system turnover plans and certain near-term milestone dates. Other milestone dates did not change. Achievement of the February 2020 aggressive site work plan relied on meeting increased monthly production and activity target values during 2020. In mid-March 2020, Southern Nuclear began implementing policies and procedures designed to mitigate the risk of transmission of COVID-19 at the construction site, including worker distancing measures, isolating individuals who have tested positive for COVID-19, are showing symptoms consistent with COVID-19, are being tested for COVID-19, or have been in close contact with such persons, requiring self-quarantine, and adopting additional precautionary measures. In April 2020, Georgia Power, acting for itself and as agent for the other Vogtle Owners, announced a reduction in workforce at Plant Vogtle Units 3 and 4, which totaled approximately 20% of the then-existing site workforce. This reduction in workforce was a mitigation action intended to address the impact of the COVID-19 pandemic on the Plant Vogtle Units 3 and 4 workforce and construction site, including challenges with labor productivity that were exacerbated by the impact of the COVID-19 pandemic. The April 2020 workforce reduction was intended to provide operational efficiencies by increasing productivity of the remaining workforce and reducing workforce fatigue and absenteeism. Further, it was also intended to allow for increased social distancing by the workforce and facilitate compliance with the recommendations from the Centers for Disease Control and Prevention. The April 2020 workforce reduction did reduce absenteeism, providing an improvement in operational efficiency and allowing for increased social distancing. From the initial peak in April 2020, the number of active cases at the site declined significantly during May and early June, but began increasing again from mid-June through July, and continued to impact productivity levels and pace of activity completion. As a result of these factors, overall production improvements were not achieved at the levels anticipated, contributing to the June 30, 2020 allocation of, and increase in, construction contingency described above. Through mid-July 2020, Unit 3 mechanical, electrical, and subcontract activities continued to build a backlog to Southern Nuclear's February 2020 aggressive site work plan. To address these issues, in July 2020, Southern Nuclear updated its aggressive site work plan for both Unit 3 and Unit 4. Through October 2020, the project has faced challenges in meeting the July 2020 aggressive site work plan targets including, but not limited to, overall construction and subcontractor labor productivity, which has resulted in a backlog of activities and completion percentages below the July 2020 aggressive site work plan targets. In addition, while the number of active COVID-19 cases at the site has declined since July 2020, the COVID-19 pandemic continues to impact productivity and the pace of activity completion. After considering these factors, Southern Nuclear has further extended milestone dates from the July 2020 aggressive site work plan. Achievement of these extended milestone dates depends on absenteeism rates continuing to normalize and overall construction productivity and production levels, including subcontractors, significantly improving and being sustained above pre-pandemic levels. In addition, appropriate levels of craft laborers, particularly electrical and pipefitter craft labor, need to be added and maintained. Georgia Power still expects to achieve the regulatory-approved in-service dates of November 2021 and November 2022 for Plant Vogtle Units 3 and 4, respectively. Southern Nuclear and Georgia Power continue to believe that pursuit of an aggressive site work plan is an appropriate strategy to achieve completion of the units by their regulatory-approved in-service dates. As construction, including subcontract work, continues and testing and system turnover activities increase, challenges with management of contractors and vendors; subcontractor performance; supervision of craft labor and related productivity, particularly in the installation of electrical, mechanical, and instrumentation and controls commodities, ability to attract and retain craft labor, and/or related cost escalation; procurement, fabrication, delivery, assembly, installation, system turnover, and the initial testing and start-up, including any required engineering changes or any remediation related thereto, of plant systems, structures, or components (some of which are based on new technology that only within the last few years began initial operation in the global nuclear industry at this scale), any of which may require additional labor and/or materials; or other issues could arise and change the projected schedule and estimated cost. In addition, the continuing effects of the COVID-19 pandemic could further disrupt or delay construction, testing, supervisory, and support activities at Plant Vogtle Units 3 and 4. Georgia Power's proportionate share of the estimated incremental cost associated with COVID-19 mitigation actions and impacts on construction productivity is currently estimated to be between $70 million and $115 million, which is included in the total project capital cost forecast and assumes (i) absenteeism rates continue to normalize and (ii) the intended productivity efficiencies and production targets assumed in Southern Nuclear's July 2020 aggressive site work plan are realized in the coming months. However, the ultimate impact of the COVID-19 pandemic on the construction schedule and budget for Plant Vogtle Units 3 and 4 cannot be determined at this time. There have been technical and procedural challenges to the construction and licensing of Plant Vogtle Units 3 and 4 at the federal and state level and additional challenges may arise. Processes are in place that are designed to assure compliance with the requirements specified in the Westinghouse Design Control Document and the combined construction and operating licenses, including inspections by Southern Nuclear and the NRC that occur throughout construction. As a result of such compliance processes, certain license amendment requests have been filed and approved or are pending before the NRC. Various design and other licensing-based compliance matters, including the timely submittal by Southern Nuclear of the ITAAC documentation for each unit and the related reviews and approvals by the NRC necessary to support NRC authorization to load fuel, may arise, which may result in additional license amendments or require other resolution. As part of the aggressive site work plan, in January 2020, Southern Nuclear notified the NRC of its intent to load fuel in 2020. On June 15, 2020, the NRC rejected Nuclear Watch South's April 20, 2020 petition requesting a hearing and challenging the closure of certain ITAAC. On August 10, 2020, the Atomic Safety and Licensing Board rejected the Blue Ridge Environmental Defense League's (BREDL) May 11, 2020 petition challenging a license amendment request. The staff of the NRC has issued the requested amendment to the combined construction and operating license for Plant Vogtle Unit 3. BREDL appealed the Atomic Safety and Licensing Board decision to the NRC. If any license amendment requests or other licensing-based compliance issues are not resolved in a timely manner, there may be delays in the project schedule that could result in increased costs. The ultimate outcome of these matters cannot be determined at this time. However, any extension of the regulatory-approved project schedule is currently estimated to result in additional base capital costs of approximately $50 million per month, based on Georgia Power's ownership interests, and AFUDC of approximately $10 million per month. While Georgia Power is not precluded from seeking recovery of any future capital cost forecast increase, management will ultimately determine whether or not to seek recovery. Any further changes to the capital cost forecast that are not expected to be recoverable through regulated rates will be required to be charged to income and such charges could be material. Joint Owner Contracts In November 2017, the Vogtle Owners entered into an amendment to their joint ownership agreements for Plant Vogtle Units 3 and 4 to provide for, among other conditions, additional Vogtle Owner approval requirements. Effective in August 2018, the Vogtle Owners further amended the joint ownership agreements to clarify and provide procedures for certain provisions of the joint ownership agreements related to adverse events that require the vote of the holders of at least 90% of the ownership interests in Plant Vogtle Units 3 and 4 to continue construction (as amended, and together with the November 2017 amendment, the Vogtle Joint Ownership Agreements). The Vogtle Joint Ownership Agreements also confirm that the Vogtle Owners' sole recourse against Georgia Power or Southern Nuclear for any action or inaction in connection with their performance as agent for the Vogtle Owners is limited to removal of Georgia Power and/or Southern Nuclear as agent, except in cases of willful misconduct. As a result of an increase in the total project capital cost forecast and Georgia Power's decision not to seek rate recovery of the increase in the base capital costs in conjunction with the nineteenth VCM report in 2018, the holders of at least 90% of the ownership interests in Plant Vogtle Units 3 and 4 were required to vote to continue construction. In September 2018, the Vogtle Owners unanimously voted to continue construction of Plant Vogtle Units 3 and 4. Amendments to the Vogtle Joint Ownership Agreements In connection with the vote to continue construction, Georgia Power entered into (i) a binding term sheet (Vogtle Owner Term Sheet) with the other Vogtle Owners and MEAG Power's wholly-owned subsidiaries MEAG Power SPVJ, LLC (MEAG SPVJ), MEAG Power SPVM, LLC (MEAG SPVM), and MEAG Power SPVP, LLC (MEAG SPVP) to take certain actions which partially mitigate potential financial exposure for the other Vogtle Owners, including additional amendments to the Vogtle Joint Ownership Agreements and the purchase of PTCs from the other Vogtle Owners at pre-established prices, and (ii) a term sheet (MEAG Term Sheet) with MEAG Power and MEAG SPVJ to provide up to $300 million of funding with respect to MEAG SPVJ's ownership interest in Plant Vogtle Units 3 and 4 under certain circumstances. In January 2019, Georgia Power, MEAG Power, and MEAG SPVJ entered into an agreement to implement the provisions of the MEAG Term Sheet. In February 2019, Georgia Power, the other Vogtle Owners, and MEAG Power's wholly-owned subsidiaries MEAG SPVJ, MEAG SPVM, and MEAG SPVP entered into certain amendments to the Vogtle Joint Ownership Agreements to implement the provisions of the Vogtle Owner Term Sheet (Global Amendments). As previously disclosed, pursuant to the Global Amendments: (i) each Vogtle Owner must pay its proportionate share of qualifying construction costs for Plant Vogtle Units 3 and 4 based on its ownership percentage up to the estimated cost at completion (EAC) for Plant Vogtle Units 3 and 4 which formed the basis of Georgia Power's forecast of $8.4 billion in the nineteenth VCM plus $800 million; (ii) Georgia Power will be responsible for 55.7% of actual qualifying construction costs between $800 million and $1.6 billion over the EAC in the nineteenth VCM (resulting in $80 million of potential additional costs to Georgia Power), with the remaining Vogtle Owners responsible for 44.3% of such costs pro rata in accordance with their respective ownership interests; and (iii) Georgia Power will be responsible for 65.7% of qualifying construction costs between $1.6 billion and $2.1 billion over the EAC in the nineteenth VCM (resulting in a further $100 million of potential additional costs to Georgia Power), with the remaining Vogtle Owners responsible for 34.3% of such costs pro rata in accordance with their respective ownership interests. If the EAC is revised and exceeds the EAC in the nineteenth VCM by more than $2.1 billion, each of the other Vogtle Owners will have a one-time option at the time the project budget forecast is so revised to tender a portion of its ownership interest to Georgia Power in exchange for Georgia Power's agreement to pay 100% of such Vogtle Owner's remaining share of total construction costs in excess of the EAC in the nineteenth VCM plus $2.1 billion. In addition, pursuant to the Global Amendments, the holders of at least 90% of the ownership interests in Plant Vogtle Units 3 and 4 must vote to continue construction if certain adverse events occur, including, among other events: (i) the bankruptcy of Toshiba; (ii) the termination or rejection in bankruptcy of certain agreements, including the Vogtle Services Agreement, the Bechtel Agreement, or the agency agreement with Southern Nuclear; (iii) Georgia Power's public announcement of its intention not to submit for rate recovery any portion of its investment in Plant Vogtle Units 3 and 4 or the Georgia PSC determines that any of Georgia Power's costs relating to the construction of Plant Vogtle Units 3 and 4 will not be recovered in retail rates, excluding any additional amounts paid by Georgia Power on behalf of the other Vogtle Owners pursuant to the Global Amendments described above and the first 6% of costs during any six-month VCM reporting period that are disallowed by the Georgia PSC for recovery, or for which Georgia Power elects not to seek cost recovery, through retail rates; and (iv) an incremental extension of one year or more over the most recently approved schedule. The ultimate outcome of these matters cannot be determined at this time. Regulatory Matters In 2009, the Georgia PSC voted to certify construction of Plant Vogtle Units 3 and 4 with a certified capital cost of $4.418 billion. In addition, in 2009 the Georgia PSC approved inclusion of the Plant Vogtle Units 3 and 4 related CWIP accounts in rate base, and the State of Georgia enacted the Georgia Nuclear Energy Financing Act, which allows Georgia Power to recover financing costs for Plant Vogtle Units 3 and 4. Financing costs are recovered on all applicable certified costs through annual adjustments to the NCCR tariff up to the certified capital cost of $4.418 billion. At September 30, 2020, Georgia Power had recovered approximately $2.5 billion of financing costs. Financing costs related to capital costs above $4.418 billion are being recognized through AFUDC and are expected to be recovered through retail rates over the life of Plant Vogtle Units 3 and 4; however, Georgia Power will not record AFUDC related to any capital costs in excess of the total deemed reasonable by the Georgia PSC (currently $7.3 billion) and not requested for rate recovery. On October 1, 2020, Georgia Power filed a request to decrease the NCCR tariff by $142 million annually, effective January 1, 2021, pending Georgia PSC approval. Georgia Power is required to file semi-annual VCM reports with the Georgia PSC by February 28 and August 31 of each year. In 2013, in connection with the eighth VCM report, the Georgia PSC approved a stipulation between Georgia Power and the staff of the Georgia PSC to waive the requirement to amend the Plant Vogtle Units 3 and 4 certificate in accordance with the 2009 certification order until the completion of Plant Vogtle Unit 3, or earlier if deemed appropriate by the Georgia PSC and Georgia Power. In 2016, the Georgia PSC voted to approve a settlement agreement (Vogtle Cost Settlement Agreement) resolving certain prudency matters in connection with the fifteenth VCM report. In December 2017, the Georgia PSC voted to approve (and issued its related order on January 11, 2018) Georgia Power's seventeenth VCM report and modified the Vogtle Cost Settlement Agreement. The Vogtle Cost Settlement Agreement, as modified by the January 11, 2018 order, resolved the following regulatory matters related to Plant Vogtle Units 3 and 4: (i) none of the $3.3 billion of costs incurred through December 31, 2015 and reflected in the fourteenth VCM report should be disallowed from rate base on the basis of imprudence; (ii) the Contractor Settlement Agreement was reasonable and prudent and none of the amounts paid pursuant to the Contractor Settlement Agreement should be disallowed from rate base on the basis of imprudence; (iii) (a) capital costs incurred up to $5.68 billion would be presumed to be reasonable and prudent with the burden of proof on any party challenging such costs, (b) Georgia Power would have the burden to show that any capital costs above $5.68 billion were prudent, and (c) a revised capital cost forecast of $7.3 billion (after reflecting the impact of payments received under the Guarantee Settlement Agreement and related customer refunds) was found reasonable; (iv) construction of Plant Vogtle Units 3 and 4 should be completed, with Southern Nuclear serving as project manager and Bechtel as primary contractor; (v) approved and deemed reasonable Georgia Power's revised schedule placing Plant Vogtle Units 3 and 4 in service in November 2021 and November 2022, respectively; (vi) confirmed that the revised cost forecast does not represent a cost cap and that prudence decisions on cost recovery will be made at a later date, consistent with applicable Georgia law; (vii) reduced the ROE used to calculate the NCCR tariff (a) from 10.95% (the ROE rate setting point authorized by the Georgia PSC in the 2013 ARP) to 10.00% effective January 1, 2016, (b) from 10.00% to 8.30%, effective January 1, 2020, and (c) from 8.30% to 5.30%, effective January 1, 2021 (provided that the ROE in no case will be less than Georgia Power's average cost of long-term debt); (viii) reduced the ROE used for AFUDC equity for Plant Vogtle Units 3 and 4 from 10.00% to Georgia Power's average cost of long-term debt, effective January 1, 2018; and (ix) agreed that upon Unit 3 reaching commercial operation, retail base rates would be adjusted to

CONTINGENCIES

CONTINGENCIES	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
CONTINGENCIES	CONTINGENCIESSee Note 3 to the financial statements in Item 8 of the Form 10-K for information relating to various lawsuits and other contingencies. General Litigation Matters The Registrants are involved in various other matters being litigated and regulatory matters. The ultimate outcome of such pending or potential litigation or regulatory matters against each Registrant and any subsidiaries cannot be determined at this time; however, for current proceedings not specifically reported herein, management does not anticipate that the ultimate liabilities, if any, arising from such current proceedings would have a material effect on such Registrant's financial statements. The Registrants believe the pending legal challenges discussed below have no merit; however, the ultimate outcome of these matters cannot be determined at this time. Southern Company In January 2017, a securities class action complaint was filed in the U.S. District Court for the Northern District of Georgia by Monroe County Employees' Retirement System on behalf of all persons who purchased shares of Southern Company's common stock between April 25, 2012 and October 29, 2013. The complaint names as defendants Southern Company, certain of its current and former officers, and certain former Mississippi Power officers and alleges that the defendants made materially false and misleading statements regarding the Kemper County energy facility in violation of certain provisions under the Securities Exchange Act of 1934, as amended. The complaint seeks, among other things, compensatory damages and litigation costs and attorneys' fees. In 2017, the plaintiffs filed an amended complaint that provided additional detail about their claims, increased the purported class period by one day, and added certain other former Mississippi Power officers as defendants. Also in 2017, the defendants filed a motion to dismiss the plaintiffs' amended complaint with prejudice, to which the plaintiffs filed an opposition. In 2018, the court issued an order dismissing certain claims against certain officers of Southern Company and Mississippi Power and dismissing the allegations related to a number of the statements that plaintiffs challenged as being false or misleading. In 2018, the court denied the defendants' motion for reconsideration and also denied a motion to certify the issue for interlocutory appeal. In the third quarter 2019, the court certified the plaintiffs' proposed class and the defendants filed a petition for interlocutory appeal of the class certification order with the U.S. Court of Appeals for the Eleventh Circuit. In December 2019, the U.S. District Court for the Northern District of Georgia entered an order staying all deadlines in the case pending mediation. The stay automatically expired on March 31, 2020; however, in light of the COVID-19 pandemic, the U.S. District Court for the Northern District of Georgia vacated all existing discovery deadlines until June 15, 2020. On June 30, 2020, the court entered a revised scheduling order, which resumed discovery and set out remaining case deadlines. On August 15, 2020, the parties reached a settlement. On September 8, 2020, the plaintiffs filed a stipulation of settlement and motion for preliminary approval to resolve the case on a class-wide basis, which the court granted on October 1, 2020. The settlement amount will be paid entirely through existing insurance policies and is not expected to have a material impact on Southern Company's financial statements. In February 2017, Jean Vineyard and Judy Mesirov each filed a shareholder derivative lawsuit in the U.S. District Court for the Northern District of Georgia. Each of these lawsuits names as defendants Southern Company, certain of its directors, certain of its current and former officers, and certain former Mississippi Power officers. In 2017, these two shareholder derivative lawsuits were consolidated in the U.S. District Court for the Northern District of Georgia. The complaints allege that the defendants caused Southern Company to make false or misleading statements regarding the Kemper County energy facility cost and schedule. Further, the complaints allege that the defendants were unjustly enriched and caused the waste of corporate assets and also allege that the individual defendants violated their fiduciary duties. Each plaintiff seeks to recover, on behalf of Southern Company, unspecified actual damages and, on each plaintiff's own behalf, attorneys' fees and costs in bringing the lawsuit. Each plaintiff also seeks certain changes to Southern Company's corporate governance and internal processes. In 2018, the court entered an order staying this lawsuit until 30 days after the resolution of any dispositive motions or any settlement, whichever is earlier, in the securities class action. On September 25, 2020, the plaintiffs filed a status report noting the settlement of the securities class action and informing the court that the parties have scheduled mediation of this case later in the fourth quarter 2020. In May 2017, Helen E. Piper Survivor's Trust filed a shareholder derivative lawsuit in the Superior Court of Gwinnett County, Georgia that names as defendants Southern Company, certain of its directors, certain of its current and former officers, and certain former Mississippi Power officers. The complaint alleges that the individual defendants, among other things, breached their fiduciary duties in connection with schedule delays and cost overruns associated with the construction of the Kemper County energy facility. The complaint further alleges that the individual defendants authorized or failed to correct false and misleading statements regarding the Kemper County energy facility schedule and cost and failed to implement necessary internal controls to prevent harm to Southern Company. The plaintiff seeks to recover, on behalf of Southern Company, unspecified actual damages and disgorgement of profits and, on its behalf, attorneys' fees and costs in bringing the lawsuit. The plaintiff also seeks certain unspecified changes to Southern Company's corporate governance and internal processes. In 2018, the court entered an order staying this lawsuit until 30 days after the resolution of any dispositive motions or any settlement, whichever is earlier, in the securities class action. In August 2019, the court granted a motion filed by the plaintiff in July 2019 to substitute a new named plaintiff, Martin J. Kobuck, in place of Helen E. Piper Survivor's Trust. On September 30, 2020, the plaintiffs filed a status report noting the settlement of the securities class action and informing the court that the parties have scheduled mediation of this case later in the fourth quarter 2020. Georgia Power In 2011, plaintiffs filed a putative class action against Georgia Power in the Superior Court of Fulton County, Georgia alleging that Georgia Power's collection in rates of amounts for municipal franchise fees (which fees are paid to municipalities) exceeded the amounts allowed in orders of the Georgia PSC and alleging certain state law claims. This case has been ruled upon and appealed numerous times over the last several years. In one recent appeal, the Georgia Supreme Court remanded the case and noted that the trial court could refer the matter to the Georgia PSC to interpret its tariffs. Following a motion by Georgia Power, in February 2019, the Superior Court of Fulton County ordered the parties to submit petitions to the Georgia PSC for a declaratory ruling and also conditionally certified the proposed class. In March 2019, Georgia Power and the plaintiffs filed petitions with the Georgia PSC seeking confirmation of the proper application of the municipal franchise fee schedule pursuant to the Georgia PSC's orders. Also in March 2019, Georgia Power appealed the class certification decision to the Georgia Court of Appeals. In October 2019, the Georgia PSC issued an order that found Georgia Power has appropriately implemented the municipal franchise fee schedule. On March 11, 2020, the Georgia Court of Appeals vacated the Superior Court of Fulton County's February 2019 order granting conditional class certification. The Court of Appeals remanded the case to the Superior Court of Fulton County for further proceedings. In September 2020, the plaintiffs and Georgia Power each filed motions for summary judgment on all claims and the plaintiffs renewed their motion for class certification. The amount of any possible losses cannot be calculated at this time because, among other factors, it is unknown whether a class will be certified, the ultimate composition of any class, and whether any losses would be subject to recovery from any municipalities. On July 29, 2020, a group of individual plaintiffs filed a complaint in the Superior Court of Fulton County, Georgia against Georgia Power alleging that releases from Plant Scherer have impacted groundwater, surface water, and air, resulting in alleged personal injuries and property damage. The plaintiffs seek an unspecified amount of monetary damages including punitive damages, a medical monitoring fund, and injunctive relief. Mississippi Power In May 2018, Southern Company and Mississippi Power received a notice of dispute and arbitration demand filed by Martin Product Sales, LLC (Martin) based on two agreements, both related to Kemper IGCC byproducts for which Mississippi Power provided termination notices in 2017. Martin alleges breach of contract, breach of good faith and fair dealing, fraud and misrepresentation, and civil conspiracy and makes a claim for damages in the amount of approximately $143 million, as well as additional unspecified damages, attorney's fees, costs, and interest. A portion of the claim for damages was on behalf of Martin Transport, Inc. (Martin Transport), an affiliate of Martin. In May 2019, the arbitration panel denied Mississippi Power's and Southern Company's motions to dismiss. In September 2019, Martin Transport filed a separate complaint against Mississippi Power in the Circuit Court of Kemper County, Mississippi alleging claims of fraud, negligent misrepresentation, promissory estoppel, and equitable estoppel, each arising out of the same alleged facts and circumstances that underlie Martin's arbitration demand. Martin Transport seeks compensatory damages of $5 million and punitive damages of $50 million. In November 2019, Martin Transport's claim was combined with the Martin arbitration case and the separate court case was dismissed. In December 2019, Southern Company and Mississippi Power each filed motions for summary judgment on all claims. On February 17, 2020, the arbitration panel granted Southern Company's motion and dismissed Southern Company from the arbitration. On March 12, 2020, the arbitration panel denied Mississippi Power's motions for summary judgment. During the third quarter 2020, the plaintiffs reduced their claim for damages to approximately $76 million. On October 12, 2020, the arbitration panel issued a unanimous award in favor of Mississippi Power on all claims. This matter is now concluded. In November 2018, Ray C. Turnage and 10 other individual plaintiffs filed a putative class action complaint against Mississippi Power and the three then-serving members of the Mississippi PSC in the U.S. District Court for the Southern District of Mississippi. Mississippi Power received Mississippi PSC approval in 2013 to charge a mirror CWIP rate premised upon including in its rate base pre-construction and construction costs for the Kemper IGCC prior to placing the Kemper IGCC into service. The Mississippi Supreme Court reversed that approval and ordered Mississippi Power to refund the amounts paid by customers under the previously-approved mirror CWIP rate. The plaintiffs allege that the initial approval process, and the amount approved, were improper. They also allege that Mississippi Power underpaid customers by up to $23.5 million in the refund process by applying an incorrect interest rate. The plaintiffs seek to recover, on behalf of themselves and their putative class, actual damages, punitive damages, pre-judgment interest, post-judgment interest, attorney's fees, and costs. In response to Mississippi Power and the Mississippi PSC each filing a motion to dismiss, the plaintiffs filed an amended complaint in March 2019. The amended complaint included four additional plaintiffs and additional claims for gross negligence, reckless conduct, and intentional wrongdoing. Mississippi Power and the Mississippi PSC have each filed a motion to dismiss the amended complaint. On March 27, 2020, the Mississippi PSC's motion to dismiss was granted. Also on March 27, 2020, the plaintiffs filed a motion seeking to name the new members of the Mississippi PSC, the Mississippi Development Authority, and Southern Company as additional defendants and add a cause of action against all defendants based on a dormant commerce clause theory under the U.S. Constitution. On April 9, 2020 and April 10, 2020, Mississippi Power and the Mississippi PSC, respectively, filed responses opposing the motion for leave to file a second amended complaint. On May 26, 2020, the court granted Mississippi Power's motion to dismiss the first amended complaint filed in 2019. On July 6, 2020, the plaintiffs filed a motion for revision of the court's decision. The plaintiffs' motion for leave to file a second amended complaint also remains pending before the court. On July 28, 2020, the plaintiffs filed a motion for leave to file a third amended complaint, which includes the same federal claims as the proposed second amended complaint, as well as several additional state law claims based on the allegation that Mississippi Power failed to disclose the annual percentage rate of interest applicable to refunds. An adverse outcome in this proceeding could have a material impact on Mississippi Power's financial statements. See Note 2 to the financial statements under "Mississippi Power – Kemper County Energy Facility" in Item 8 of the Form 10-K for additional information. Environmental Remediation The Southern Company system must comply with environmental laws and regulations governing the handling and disposal of waste and releases of hazardous substances. Under these various laws and regulations, the Southern Company system could incur substantial costs to clean up affected sites. The traditional electric operating companies and the natural gas distribution utilities in Illinois and Georgia have each received authority from their respective state PSCs or other applicable state regulatory agencies to recover approved environmental compliance costs through regulatory mechanisms. These regulatory mechanisms are adjusted annually or as necessary within limits approved by the state PSCs or other applicable state regulatory agencies. Georgia Power's environmental remediation liability was $15 million at both September 30, 2020 and December 31, 2019. Georgia Power has been designated or identified as a potentially responsible party at sites governed by the Georgia Hazardous Site Response Act and/or by the federal Comprehensive Environmental Response, Compensation, and Liability Act, and assessment and potential cleanup of such sites is expected. In December 2019, Mississippi Power entered into an agreement with the Mississippi Commission on Environmental Quality related to groundwater conditions arising from the closed ash pond at Plant Watson. Mississippi Power will complete an assessment and remediation consistent with the requirements of the agreement and the CCR Rule. Potential remediation activities and related cost estimates are pending the result of further site assessment and cannot be determined at this time. Mississippi Power expects to recover the retail portion of remedial costs through the ECO Plan and the wholesale portion through MRA rates. Southern Company Gas' environmental remediation liability was $252 million and $269 million as of September 30, 2020 and December 31, 2019, respectively, based on the estimated cost of environmental investigation and remediation associated with known current and former manufactured gas plant operating sites. These environmental remediation expenditures are generally recoverable from customers through rate mechanisms approved by the applicable state regulatory agencies of the natural gas distribution utilities. The ultimate outcome of these matters cannot be determined at this time; however, as a result of the regulatory treatment for environmental remediation expenses described above, the final disposition of these matters is not expected to have a material impact on the financial statements of the applicable Registrants. Nuclear Fuel Disposal Costs On August 13, 2020, Alabama Power and Georgia Power filed amended complaints in each of the lawsuits against the U.S. government in the Court of Federal Claims for the costs of continuing to store spent nuclear fuel at Plants Farley, Hatch, and Vogtle Units 1 and 2. The amended complaints add damages from January 1, 2018 to December 31, 2019 to the claim period. Damages will continue to accumulate until the issue is resolved, the U.S. government disposes of Alabama Power's and Georgia Power's spent nuclear fuel pursuant to its contractual obligations, or alternative storage is otherwise provided. No amounts have been recognized in the financial statements as of September 30, 2020 for any potential recoveries from the pending lawsuits. The final outcome of these matters cannot be determined at this time. However, Alabama Power and Georgia Power expect to credit any recoveries for Other Matters Southern Company See Notes 1 and 3 under "Leveraged Leases" and "Other Matters – Southern Company," respectively, in Item 8 of the Form 10-K for discussion of challenges associated with a leveraged lease agreement with a subsidiary of Southern Holdings. While all required lease payments through September 30, 2020 have been paid in full, the operational and remarketing risks and the resulting cash liquidity challenges persist and significant concerns continue regarding the lessee's ability to make the remaining required semi-annual lease payments to the Southern Holdings subsidiary through the term of the lease. In its annual impairment analysis of the expected residual value of the generation assets and the overall collectability of the related lease receivable, Southern Company uses multiple scenarios of long-term market energy prices to estimate the cash flows expected to be received from remarketing the generation assets following the expiration of the existing PPA in 2032 and the residual value of the generation assets at the end of the lease in 2047. Southern Company received the latest annual forecasts of natural gas prices during the second quarter 2020 and considered the significant decline in forecasted prices to be an indicator of potential impairment that required an interim impairment assessment. Accordingly, consistent with prior years, Southern Company evaluated the recoverability of the lease receivable and the expected residual value of the generation assets under various natural gas price scenarios. Based on the current forecasts of energy prices in the years following the expiration of the existing PPA, Southern Company concluded that it is no longer probable that any of the associated rental payments will be received, because it is no longer probable the generation assets will be successfully remarketed and continue to operate after that date. During the second quarter 2020, Southern Company revised the estimated cash flows to be received under the leveraged lease to reflect this conclusion, which resulted in a full impairment of the lease investment and a pre-tax charge to earnings of $154 million ($74 million after tax). If any future lease payment due prior to the expiration of the associated PPA is not paid in full, the Southern Holdings subsidiary may be unable to make its corresponding payment to the holders of the underlying non-recourse debt related to the generation assets. Failure to make the required payment to the debtholders could represent an event of default that would give the debtholders the right to foreclose on, and take ownership of, the generation assets, in effect terminating the lease. As the remaining amount of the lease investment was charged against earnings in the second quarter 2020, termination would not be expected to result in additional charges. Southern Company will continue to monitor the operational performance of the underlying assets and evaluate the ability of the lessee to continue to make the required lease payments and meet its obligations associated with a future closure or retirement of the generation assets and associated properties, including the dry ash landfill. Mississippi Power Kemper County Energy Facility See Note 2 to the financial statements under "Mississippi Power – Kemper County Energy Facility" in Item 8 of the Form 10-K for additional information. As the mining permit holder, Liberty Fuels Company, LLC has a legal obligation to perform mine reclamation and Mississippi Power has a contractual obligation to fund all reclamation activities related to the lignite mine and equipment and mineral reserves located around the Kemper County energy facility site. As a result of the abandonment of the Kemper IGCC, final mine reclamation began in 2018 and is expected to be substantially completed in 2020, with monitoring expected to continue through 2027. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. For year-to-date 2020, Mississippi Power recorded pre-tax (and after-tax) charges to income totaling $2 million primarily associated with abandonment and related closure costs and ongoing period costs, net of salvage proceeds, for the mine and gasifier-related assets at the Kemper County energy facility. Dismantlement of the abandoned gasifier-related assets and site restoration activities are expected to be completed in 2025. The additional pre-tax period costs associated with dismantlement and site restoration activities, including related costs for compliance and safety, ARO accretion, and property taxes, net of salvage, are estimated to total $3 million for the remainder of 2020 and $10 million to $15 million annually for 2021 through 2025. In December 2019, Mississippi Power transferred ownership of the CO 2 pipeline to an unrelated gas pipeline company, with no resulting impact on income. In conjunction with the transfer of the CO 2 pipeline, the parties agreed to enter into a 15-year firm transportation agreement, which is expected to be signed by the end of 2020, providing for the conversion by the pipeline company of the CO 2 pipeline to a natural gas pipeline to be used for the delivery of natural gas to Plant Ratcliffe. The agreement is expected to be treated as a finance lease for accounting purposes upon commencement. On September 3, 2020, Mississippi Power and Southern Company executed an agreement with the DOE completing Mississippi Power's request for property closeout certification under the contract related to the DOE grants received for the Kemper County energy facility, which enables Mississippi Power to proceed with full dismantlement of the abandoned gasifier-related assets and site restoration activities. The execution of the agreement had no material impact on Mississippi Power's financial statements. In connection with the DOE closeout discussions, in April 2019, the Civil Division of the Department of Justice informed Southern Company and Mississippi Power of an investigation related to the $387 million of DOE grants received. The ultimate outcome of this matter cannot be determined at this time; however, it could have a material impact on Southern Company's and Mississippi Power's financial statements. Plant Daniel In conjunction with Southern Company's sale of Gulf Power, Mississippi Power and Gulf Power agreed to seek a restructuring of their 50% undivided ownership interests in Plant Daniel such that each of them would, after the restructuring, own 100% of a generating unit. On April 24, 2020, Mississippi Power and Gulf Power amended the terms of the agreement to extend the deadline from May 1, 2020 to August 1, 2020 for Mississippi Power to notify Gulf Power of which generating unit it has selected for 100% ownership. The parties agreed not to select a specific unit by August 1, 2020 and are continuing negotiations on a mutually acceptable revised operating agreement. The impacts of operating the units on an individual basis continue to be evaluated by Mississippi Power and any transfer of ownership would be subject to approval by the FERC and the Mississippi PSC. The ultimate outcome of this matter cannot be determined at this time. Southern Company Gas See Notes 3 and 7 to the financial statements in Item 8 of the Form 10-K under "Other Matters – Southern Company Gas" and "Southern Company Gas," respectively, and Note (E) under "Southern Company Gas" for additional information. On March 24, 2020, Southern Company Gas completed the sale of its interest in Atlantic Coast Pipeline. See Note (K) under "Southern Company Gas" for additional information. On February 20, 2020, the FERC approved a two-year extension for PennEast Pipeline to complete the project by January 19, 2022. In September 2019, an appellate court ruled that the PennEast Pipeline does not have federal eminent domain authority over lands in which a state has property rights interests. On June 29, 2020, the U.S. Supreme Court requested the U.S. Solicitor General to provide an opinion on PennEast Pipeline's petition for a writ of certiorari seeking its review of the appellate court's decision. Expected project costs related to the PennEast Pipeline for Southern Company Gas total approximately $300 million, excluding financing costs. The ultimate outcome of the PennEast Pipeline construction project cannot be determined at this time; however, any work delays, whether caused by judicial or regulatory action, abnormal weather, or other conditions, may result in additional cost or schedule modifications or, ultimately, in project

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME	REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME Revenue from Contracts with Customers The Registrants generate revenues from a variety of sources, some of which are not accounted for as revenue from contracts with customers, such as leases, derivatives, and certain cost recovery mechanisms. See Note 1 to the financial statements under "Revenues" in Item 8 of the Form 10-K for additional information on the revenue policies of the Registrants. See "Lease Income" herein and Note (J) for additional information on revenue accounted for under lease and derivative accounting guidance, respectively. The following table disaggregates revenue from contracts with customers for the three and nine months ended September 30, 2020 and 2019: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Three Months Ended September 30, 2020 Operating revenues Retail electric revenues Residential $ 2,019 $ 752 $ 1,183 $ 84 $ — $ — Commercial 1,354 447 833 74 — — Industrial 783 358 352 73 — — Other 22 5 15 2 — — Total retail electric revenues 4,178 1,562 2,383 233 — — Natural gas distribution revenues Residential 170 — — — — 170 Commercial 41 — — — — 41 Transportation 224 — — — — 224 Industrial 4 — — — — 4 Other 35 — — — — 35 Total natural gas distribution revenues 474 — — — — 474 Wholesale electric revenues PPA energy revenues 214 40 13 2 165 — PPA capacity revenues 136 26 15 1 95 — Non-PPA revenues 59 10 3 93 68 — Total wholesale electric revenues 409 76 31 96 328 — Other natural gas revenues Wholesale gas services 431 — — — — 431 Gas marketing services 38 — — — — 38 Other natural gas revenues 7 — — — — 7 Total natural gas revenues 476 — — — — 476 Other revenues 218 33 115 6 4 — Total revenue from contracts with customers 5,755 1,671 2,529 335 332 950 Other revenue sources (a) 968 58 88 1 191 630 Other adjustments (b) (1,103) — — — — (1,103) Total operating revenues $ 5,620 $ 1,729 $ 2,617 $ 336 $ 523 $ 477 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Nine Months Ended September 30, 2020 Operating revenues Retail electric revenues Residential $ 4,802 $ 1,839 $ 2,760 $ 203 $ — $ — Commercial 3,589 1,152 2,242 195 — — Industrial 2,081 956 907 218 — — Other 68 16 46 6 — — Total retail electric revenues 10,540 3,963 5,955 622 — — Natural gas distribution revenues Residential 906 — — — — 906 Commercial 229 — — — — 229 Transportation 723 — — — — 723 Industrial 21 — — — — 21 Other 179 — — — — 179 Total natural gas distribution revenues 2,058 — — — — 2,058 Wholesale electric revenues PPA energy revenues 550 94 38 7 425 — PPA capacity revenues 339 78 30 3 231 — Non-PPA revenues 159 33 7 235 184 — Total wholesale electric revenues 1,048 205 75 245 840 — Other natural gas revenues Wholesale gas services 1,168 — — — — 1,168 Gas marketing services 258 — — — — 258 Other natural gas revenues 22 — — — — 22 Total natural gas revenues 1,448 — — — — 1,448 Other revenues 677 117 329 19 11 — Total revenue from contracts with customers 15,771 4,285 6,359 886 851 3,506 Other revenue sources (a) 2,604 160 12 9 486 1,973 Other adjustments (b) (3,117) — — — — (3,117) Total operating revenues $ 15,258 $ 4,445 $ 6,371 $ 895 $ 1,337 $ 2,362 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Three Months Ended September 30, 2019 Operating revenues Retail electric revenues Residential $ 2,119 $ 820 $ 1,211 $ 88 $ — $ — Commercial 1,563 512 965 86 — — Industrial 953 421 450 82 — — Other 26 7 16 3 — — Total retail electric revenues 4,661 1,760 2,642 259 — — Natural gas distribution revenues Residential 162 — — — — 162 Commercial 42 — — — — 42 Transportation 204 — — — — 204 Industrial 3 — — — — 3 Other 30 — — — — 30 Total natural gas distribution revenues 441 — — — — 441 Wholesale electric revenues PPA energy revenues 245 43 19 2 188 — PPA capacity revenues 134 25 13 1 100 — Non-PPA revenues 62 2 3 111 81 — Total wholesale electric revenues 441 70 35 114 369 — Other natural gas revenues Wholesale gas services 425 — — — — 425 Gas marketing services 37 — — — — 37 Other natural gas revenues 10 — — — — 10 Total natural gas revenues 472 — — — — 472 Other revenues 267 36 113 4 3 — Total revenue from contracts with customers 6,282 1,866 2,790 377 372 913 Other revenue sources (a) 855 (25) (35) (7) 202 727 Other adjustments (b) (1,142) — — — — (1,142) Total operating revenues $ 5,995 $ 1,841 $ 2,755 $ 370 $ 574 $ 498 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Nine Months Ended September 30, 2019 Operating revenues Retail electric revenues Residential $ 4,939 $ 1,971 $ 2,751 $ 217 $ — $ — Commercial 3,951 1,301 2,427 223 — — Industrial 2,428 1,128 1,074 226 — — Other 69 20 41 8 — — Total retail electric revenues 11,387 4,420 6,293 674 — — Natural gas distribution revenues Residential 992 — — — — 992 Commercial 277 — — — — 277 Transportation 673 — — — — 673 Industrial 25 — — — — 25 Other 191 — — — — 191 Total natural gas distribution revenues 2,158 — — — — 2,158 Wholesale electric revenues PPA energy revenues 648 110 47 8 508 — PPA capacity revenues 350 77 41 2 272 — Non-PPA revenues 174 65 5 275 190 — Total wholesale electric revenues 1,172 252 93 285 970 — Other natural gas revenues Wholesale gas services 1,590 — — — — 1,590 Gas marketing services 313 — — — — 313 Other natural gas revenues 32 — — — — 32 Total natural gas revenues 1,935 — — — — 1,935 Other revenues 763 119 298 14 10 — Total revenue from contracts with customers 17,415 4,791 6,684 973 980 4,093 Other revenue sources (a) 3,266 (29) 22 (3) 547 2,744 Other adjustments (b) (4,176) — — — — (4,176) Total operating revenues $ 16,505 $ 4,762 $ 6,706 $ 970 $ 1,527 $ 2,661 (a) Other revenue sources primarily relate to revenues from customers accounted for as derivatives and leases, as well as alternative revenue programs at Southern Company Gas and other cost recovery mechanisms at the traditional electric operating companies. (b) Other adjustments relate to the cost of Southern Company Gas' energy and risk management activities. Wholesale gas services revenues are presented net of the related costs of those activities on the statement of income. See Note (L) under "Southern Company Gas" for additional information on the components of wholesale gas services' operating revenues. Contract Balances The following table reflects the closing balances of receivables, contract assets, and contract liabilities related to revenues from contracts with customers at September 30, 2020 and December 31, 2019: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Accounts Receivables As of September 30, 2020 $ 2,344 $ 686 $ 901 $ 93 $ 100 $ 385 As of December 31, 2019 2,413 586 688 79 97 749 Contract Assets As of September 30, 2020 $ 159 $ 5 $ 103 $ — $ — $ — As of December 31, 2019 117 — 69 — — — Contract Liabilities As of September 30, 2020 $ 56 $ 1 $ 24 $ — $ 3 $ 1 As of December 31, 2019 52 10 13 — 1 1 As of September 30, 2020 and December 31, 2019, Georgia Power had contract assets primarily related to fixed retail customer bill programs, where the payment is contingent upon Georgia Power's continued performance and the customer's continued participation in the program over a one-year contract term, and unregulated service agreements, where payment is contingent on project completion. Contract liabilities for Georgia Power relate to cash collections recognized in advance of revenue for certain unregulated service agreements. Alabama Power had contract liabilities for outstanding performance obligations primarily related to extended service agreements. Southern Company's unregulated distributed generation business had $47 million and $40 million of contract assets and $22 million and $28 million of contract liabilities at September 30, 2020 and December 31, 2019, respectively, for outstanding performance obligations. Revenues recognized by Southern Company in the three and nine months ended September 30, 2020, which were included in contract liabilities at December 31, 2019, were $8 million and $29 million, respectively, and immaterial for all other applicable Registrants. Remaining Performance Obligations The traditional electric operating companies and Southern Power have long-term contracts with customers in which revenues are recognized as performance obligations are satisfied over the contract term. These contracts primarily relate to PPAs whereby the traditional electric operating companies and Southern Power provide electricity and generation capacity to a customer. The revenue recognized for the delivery of electricity is variable; however, certain PPAs include a fixed payment for fixed generation capacity over the term of the contract. Southern Company's unregulated distributed generation business also has partially satisfied performance obligations related to certain fixed price contracts. Revenue from contracts with customers related to these performance obligations remaining at September 30, 2020 are expected to be recognized as follows: 2020 2021 2022 2023 2024 2025 and (in millions) Southern Company $ 170 $ 487 $ 362 $ 339 $ 319 $ 3,062 Alabama Power 7 33 31 24 7 5 Georgia Power 20 71 43 35 24 62 Southern Power 60 290 292 282 290 3,013 Revenue expected to be recognized for performance obligations remaining at September 30, 2020 w as immaterial for Mississippi Power. Lease Income Lease income for the three and nine months ended September 30, 2020 and 2019 is as follows: Southern Alabama Power Georgia Power Mississippi Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2020 Lease income - interest income on sales-type leases $ 3 $ — $ — $ 3 $ — $ — Lease income - operating leases 50 11 14 — 21 9 Variable lease income 145 — — — 153 — Total lease income $ 198 $ 11 $ 14 $ 3 $ 174 $ 9 For the Nine Months Ended September 30, 2020 Lease income - interest income on sales-type leases $ 8 $ — $ — $ 8 $ — $ — Lease income - operating leases 148 24 44 1 66 26 Variable lease income 345 — — — 368 — Total lease income $ 501 $ 24 $ 44 $ 9 $ 434 $ 26 For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 5 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 5 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26 Lease income for Southern Power is included in wholesale revenues. Lease payments received under tolling arrangements and PPAs consist of either scheduled payments or variable payments based on the amount of energy produced by the underlying electric generating units. As part of the Autauga Combined Cycle Acquisition, Alabama Power assumed an existing power sales agreement under which the full output of the generating facility remains committed to another third party for its remaining term of approximately three years. These revenues are included above as lease income from operating leases. See Note (B) and Note 15 to the financial statements in Item 8 of the Form 10-K under "Alabama Power" for additional information. Lease Receivables Mississippi Power completed construction of additional leased assets under an existing sales-type lease during the third quarter 2020. Upon completion of construction, the book value of $25 million was transferred from CWIP to lease receivables, of which $22 million and $3 million is included in other property and investments and other accounts and notes receivable, respectively, at September 30, 2020. The transfer represents a non-cash investing transaction for purposes of the statements of cash flows.

CONSOLIDATED ENTITIES AND EQUIT

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS	9 Months Ended
	Sep. 30, 2020
Regulated Operations [Abstract]
CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS	CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTSSee Note 7 to the financial statements in Item 8 of the Form 10-K for additional information. Southern Power Variable Interest Entities Southern Power has certain subsidiaries that are determined to be VIEs. Southern Power is considered the primary beneficiary of these VIEs because it controls the most significant activities of the VIEs, including operating and maintaining the respective assets, and has the obligation to absorb expected losses of these VIEs to the extent of its equity interests. SP Solar and SP Wind At September 30, 2020 and December 31, 2019, SP Solar had total assets of $6.3 billion and $6.4 billion, respectively, and total liabilities of $382 million. Noncontrolling interests totaled $1.1 billion at both September 30, 2020 and December 31, 2019. Cash distributions from SP Solar are allocated 67% to Southern Power and 33% to Global Atlantic in accordance with their partnership interest percentage. Under the terms of the limited partnership agreement, distributions without limited partner consent are limited to available cash and SP Solar is obligated to distribute all such available cash to its partners each quarter. Available cash includes all cash generated in the quarter subject to the maintenance of appropriate operating reserves. At September 30, 2020 and December 31, 2019, SP Wind had total assets of $2.4 billion and $2.5 billion, respectively, total liabilities of $129 million and $128 million, respectively, and noncontrolling interests of $44 million and $45 million, respectively. Under the terms of the limited liability agreement, distributions without Class A member consent are limited to available cash and SP Wind is obligated to distribute all such available cash to its members each quarter. Available cash includes all cash generated in the quarter subject to the maintenance of appropriate operating reserves. Cash distributions from SP Wind are generally allocated 60% to Southern Power and 40% to the three financial investors in accordance with the limited liability agreement. Southern Power consolidates both SP Solar and SP Wind, as the primary beneficiary, since it controls the most significant activities of each entity, including operating and maintaining their assets. Certain transfers and sales of the assets in the VIEs are subject to partner consent and the liabilities are non-recourse to the general credit of Southern Power. Liabilities consist of customary working capital items and do not include any long-term debt. Other Variable Interest Entities Southern Power has other consolidated VIEs that relate to certain subsidiaries that have either sold noncontrolling interests to tax-equity investors or acquired less than a 100% interest from facility developers. These entities are considered VIEs because the arrangements are structured similar to a limited partnership and the noncontrolling members do not have substantive kick-out rights. At September 30, 2020 and December 31, 2019, the other VIEs had total assets of $1.1 billion, total liabilities of $109 million and $104 million, respectively, and noncontrolling interests of $471 million and $409 million, respectively. Under the terms of the partnership agreements, distributions of all available cash are required each month or quarter and additional distributions require partner consent. Equity Method Investments At September 30, 2020 and December 31, 2019, Southern Power had equity method investments in wind and battery storage projects totaling $19 million and $28 million, respectively. Southern Company Gas Equity Method Investments On March 24, 2020, Southern Company Gas completed the sale of its interests in Pivotal LNG and Atlantic Coast Pipeline. See Note (K) under "Southern Company Gas" for additional information. The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2020 and December 31, 2019 and related income from those investments for the three and nine months ended September 30, 2020 and 2019 were as follows: Investment Balance September 30, 2020 December 31, 2019 (a) (in millions) SNG (b) $ 1,180 $ 1,137 PennEast Pipeline (c) 89 82 Other 32 32 Total $ 1,301 $ 1,251 (a) Excludes investments in Atlantic Coast Pipeline and Pivotal JAX LNG classified as held for sale at December 31, 2019. See Note 15 to the financial statements under "Assets Held for Sale" in Item 8 of the Form 10-K for additional information. (b) Increase primarily relates to a capital contribution, partially offset by the continued amortization of deferred tax assets established upon acquisition. (c) See Note (C) under "Other Matters – Southern Company Gas" for additional information on the PennEast Pipeline. Earnings from Equity Method Investments Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) SNG $ 30 $ 30 $ 95 $ 104 Atlantic Coast Pipeline (a)(b) — 3 3 9 PennEast Pipeline (a) 2 2 5 5 Other 1 — 3 (3) Total $ 33 $ 35 $ 106 $ 115 (a) Amounts primarily result from AFUDC equity recorded by the project entity. (b) On March 24, 2020, Southern Company Gas completed the sale of its interest in Atlantic Coast Pipeline. See Note (K) under "Southern Company Gas" for additional information. SNG Selected financial information of SNG for the three and nine months ended September 30, 2020 and 2019 is as follows: Income Statement Information Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) Revenues $ 150 $ 152 $ 457 $ 473 Operating income 85 82 262 274 Net income 59 60 189 208

FINANCING

FINANCING	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
FINANCING	FINANCING Bank Credit Arrangements See Note 8 to the financial statements under "Bank Credit Arrangements" in Item 8 of the Form 10-K for additional information. At September 30, 2020, committed credit arrangements with banks were as follows: Expires Company 2021 2022 2023 2024 Total Unused Due within One Year (in millions) Southern Company parent $ — $ — $ — $ 2,000 $ 2,000 $ 1,999 $ — Alabama Power 3 525 — 800 1,328 1,328 3 Georgia Power — — — 1,750 1,750 1,728 — Mississippi Power — 150 125 — 275 250 — Southern Power (a) — — — 600 600 591 — Southern Company Gas (b) — — — 1,750 1,750 1,745 — SEGCO 30 — — — 30 30 30 Southern Company $ 33 $ 675 $ 125 $ 6,900 $ 7,733 $ 7,671 $ 33 (a) Does not include Southern Power Company's $120 million and $60 million continuing letter of credit facilities for standby letters of credit expiring in 2021 and 2023, respectively, of which $23 million and $40 million, respectively, was unused at September 30, 2020. Southern Power's subsidiaries are not parties to its bank credit arrangements or letter of credit facilities. (b) Southern Company Gas, as the parent entity, guarantees the obligations of Southern Company Gas Capital, which is the borrower of $1.25 billion of this arrangement. Southern Company Gas' committed credit arrangement also includes $500 million for which Nicor Gas is the borrower and which is restricted for working capital needs of Nicor Gas. Pursuant to this multi-year credit arrangement, the allocations between Southern Company Gas Capital and Nicor Gas may be adjusted. As reflected in the table above, in March 2020, Mississippi Power entered into a $125 million revolving credit facility that matures in March 2023. Subject to applicable market conditions, Southern Company and its subsidiaries expect to renew or replace their bank credit arrangements as needed, prior to expiration. In connection therewith, Southern Company and its subsidiaries may extend the maturity dates and/or increase or decrease the lending commitments thereunder. These bank credit arrangements, as well as the term loan arrangements of the Registrants and SEGCO, contain covenants that limit debt levels and contain cross-acceleration or, in the case of Southern Power, cross-default provisions to other indebtedness (including guarantee obligations) that are restricted only to the indebtedness of the individual company. Such cross-default provisions to other indebtedness would trigger an event of default if Southern Power defaulted on indebtedness or guarantee obligations over a specified threshold. Such cross-acceleration provisions to other indebtedness would trigger an event of default if the applicable borrower defaulted on indebtedness, the payment of which was then accelerated. At September 30, 2020, the Registrants, Nicor Gas, and SEGCO were in compliance with all such covenants. None of the bank credit arrangements contain material adverse change clauses at the time of borrowings. A portion of the unused credit with banks is allocated to provide liquidity support to the revenue bonds of the traditional electric operating companies and the commercial paper programs of the Registrants, Nicor Gas, and SEGCO. The amount of variable rate revenue bonds of the traditional electric operating companies outstanding requiring liquidity support at September 30, 2020 was approximately $1.4 billion (comprised of approximately $854 million at Alabama Power, $550 million at Georgia Power, and $34 million at Mississippi Power). In addition, at September 30, 2020, Georgia Power had approximately $257 million of fixed rate revenue bonds outstanding that are required to be remarketed within the next 12 months. Earnings per Share For Southern Company, the only differences in computing basic and diluted earnings per share are attributable to awards outstanding under stock-based compensation plans and the equity units issued in August 2019. Earnings per share dilution resulting from stock-based compensation plans and the equity units issuance is determined using the treasury stock method. See Note 8 to the financial statements under "Equity Units" in Item 8 of the Form 10-K for information on the August 2019 equity units issuance and Note 12 to the financial statements in Item 8 of the Form 10-K for information on stock-based compensation plans. Shares used to compute diluted earnings per share were as follows: Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) As reported shares 1,058 1,048 1,058 1,043 Effect of stock-based compensation 6 9 6 8 Diluted shares 1,064 1,057 1,064 1,051 An immaterial number of stock-based compensation awards was not included in the diluted earnings per share calculation because the awards were anti-dilutive for the three and nine months ended September 30, 2020. There were no such amounts for the three and nine months ended September 30, 2019. An immaterial number of shares related to the equity units issued in August 2019 was included in the calculation of diluted earnings per share for the nine months ended September 30, 2020. There were no such amounts for all other periods presented.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES See Note 10 to the financial statements in Item 8 of the Form 10-K for additional tax information. Current and Deferred Income Taxes Tax Credit and Net Operating Loss Carryforwards Southern Company had federal ITC and PTC carryforwards (primarily related to Southern Power) totaling $1.5 billion as of September 30, 2020 compared to $1.8 billion as of December 31, 2019. The federal ITC and PTC carryforwards begin expiring in 2034 and 2032, respectively, but are expected to be fully utilized by 2024. The utilization of each Registrants' estimated tax credit and net operating loss carryforwards and related valuation allowances could be impacted by numerous factors, including the acquisition of additional renewable projects, the purchase of rights to additional PTCs of Plant Vogtle Units 3 and 4 pursuant to certain joint ownership agreements, potential impacts of the COVID-19 pandemic, and changes in taxable income projections. See Note (B) and Note 2 to the financial statements in Item 8 of the Form 10-K under "Georgia Power – Nuclear Construction" for additional information on Plant Vogtle Units 3 and 4. Effective Tax Rate Details of significant changes in the effective tax rate for the applicable Registrants are provided herein. Southern Company Southern Company's effective tax rate is typically lower than the statutory rate due to employee stock plans' dividend deduction, non-taxable AFUDC equity at the traditional electric operating companies, flowback of excess deferred income taxes at the regulated utilities, and federal income tax benefits from ITCs and PTCs primarily at Southern Power. Southern Company's effective tax rate was 13.9% for the nine months ended September 30, 2020 compared to 30.2% for the corresponding period in 2019. The effective tax rate decrease was primarily due to the tax impact from the sale of Gulf Power in 2019, as well as an increase in the flowback of excess deferred income taxes in 2020 primarily at Georgia Power. See Note 15 to the financial statements under "Southern Company" in Item 8 of the Form 10-K for additional information. Georgia Power Georgia Power's effective tax rate was 12.3% for the nine months ended September 30, 2020 compared to 22.6% for the corresponding period in 2019. The effective tax rate decrease was primarily due to an increase in the flowback of excess deferred income taxes in 2020 as authorized in the 2019 ARP, as well as the second quarter 2020 charge to earnings associated with the construction of Plant Vogtle Units 3 and 4. See Note (B) under "Georgia Power – Nuclear Construction" and Note 2 to the financial statements under "Georgia Power" in Item 8 of the Form 10-K for additional information. Mississippi Power Mississippi Power's effective tax rate was 12.7% for the nine months ended September 30, 2020 compared to 16.3% for the corresponding period in 2019. The effective tax rate decrease was primarily due to an increase in the flowback of excess deferred income taxes in 2020 as authorized in the Mississippi Power Rate Case Settlement Agreement. See Note (B) under "Mississippi Power – 2019 Base Rate Case" for additional information. Southern Power Southern Power's effective tax rate was 11.3% for the nine months ended September 30, 2020 compared to a benefit rate of (13.6)% for the corresponding period in 2019. The effective tax rate increase was primarily due to tax benefits resulting from ITCs recognized upon the sale of Plant Nacogdoches in 2019. See Note (K) under "Southern Power" for additional information. Southern Company Gas Southern Company Gas' effective tax rate was 21.4% for the nine months ended September 30, 2020 compared to 15.0% for the corresponding period in 2019. The effective tax rate increase was primarily due to higher flowback of excess deferred income taxes in 2019, primarily at Atlanta Gas Light as previously authorized by the Georgia PSC, and the reversal of a federal tax valuation allowance in connection with Southern Company Gas' sale of its investment in Triton in 2019. See Notes 2 and 15 to the financial statements under "Southern Company Gas" in Item 8 of the Form 10-K for additional information.

RETIREMENT BENEFITS

RETIREMENT BENEFITS	9 Months Ended
	Sep. 30, 2020
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, 2020. 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. Effective January 1, 2020, Southern Company adopted a change in method of calculating the market-related value of the liability-hedging securities included in its pension plan assets. The market-related value is used to determine the expected return on plan assets component of net periodic pension cost. Southern Company previously used the calculated value approach for all plan assets, which smoothed asset returns and deferred gains and losses by amortizing them into the calculation of the market-related value over five years. Southern Company changed to the fair value approach for liability-hedging securities, which includes measuring the market-related value of that portion of the plan assets at fair value for purposes of determining the expected return on plan assets. The remaining asset classes of plan assets will continue to use the calculated value approach in determining the market-related value. Southern Company considers the fair value approach to be preferable because it results in a current reflection of changes in the value of plan assets in the measurement of net periodic pension cost. Southern Company evaluated the effect of this change in accounting method and deemed it immaterial to the historical and current financial statements of all Registrants and therefore did not account for the change retrospectively. The change in accounting principle was recorded through earnings as a prior period adjustment for the amounts related to the unregulated businesses of Southern Company and Southern Power. Amounts related to the traditional electric operating companies and the natural gas distribution utilities have been reflected as adjustments to regulatory assets as appropriate, consistent with the expected regulatory treatment. 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, 2020 and 2019 are presented in the following tables. Three Months Ended September 30, 2020 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 94 $ 23 $ 24 $ 3 $ 2 $ 8 Interest cost 108 25 33 5 1 8 Expected return on plan assets (274) (66) (87) (13) (4) (20) Amortization: Prior service costs — 1 — — — (1) Regulatory asset — — — — — 4 Net (gain)/loss 67 17 22 4 1 2 Net periodic pension cost (income) $ (5) $ — $ (8) $ (1) $ — $ 1 Postretirement Benefits Service cost $ 6 $ 1 $ 2 $ (1) $ 1 $ — Interest cost 13 4 5 1 — 2 Expected return on plan assets (18) (7) (7) — — (2) Amortization: Prior service costs — — (1) — — — Regulatory asset — — — — — 2 Net (gain)/loss 1 — 1 — — (1) Net periodic postretirement benefit cost $ 2 $ (2) $ — $ — $ 1 $ 1 Nine Months Ended September 30, 2020 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 282 $ 67 $ 72 $ 11 $ 6 $ 24 Interest cost 324 75 100 15 4 23 Expected return on plan assets (824) (198) (261) (38) (10) (59) Amortization: Prior service costs 1 1 1 — — (2) Regulatory asset — — — — — 12 Net (gain)/loss 201 53 65 10 2 7 Net periodic pension cost (income) $ (16) $ (2) $ (23) $ (2) $ 2 $ 5 Postretirement Benefits Service cost $ 17 $ 4 $ 5 $ — $ 1 $ 1 Interest cost 40 10 15 2 — 5 Expected return on plan assets (54) (21) (20) (1) — (5) Amortization: Prior service costs (1) — (1) — — — Regulatory asset — — — — — 5 Net (gain)/loss 2 — 2 — — (2) Net periodic postretirement benefit cost $ 4 $ (7) $ 1 $ 1 $ 1 $ 4 Three Months Ended September 30, 2019 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 73 $ 17 $ 19 $ 3 $ 2 $ 7 Interest cost 123 28 38 6 1 9 Expected return on plan assets (222) (51) (73) (10) (2) (15) Amortization: Prior service costs 1 — — — — (1) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (5) $ — $ 1 $ 4 Postretirement Benefits Service cost $ 5 $ 1 $ 2 $ 1 $ — $ — Interest cost 18 4 6 — — 2 Expected return on plan assets (16) (6) (7) — — (1) Amortization: Prior service costs — 1 — — — — Regulatory asset — — — — — 1 Net (gain)/loss (1) — 1 — — — Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2 Nine Months Ended September 30, 2019 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 219 $ 51 $ 56 $ 9 $ 5 $ 19 Interest cost 369 85 116 17 4 27 Expected return on plan assets (664) (154) (219) (30) (7) (45) Amortization: Prior service costs 2 1 1 — — (2) Regulatory asset — — — — — 10 Net (gain)/loss 90 27 33 4 — 2 Net periodic pension cost (income) $ 16 $ 10 $ (13) $ — $ 2 $ 11 Postretirement Benefits Service cost $ 14 $ 3 $ 4 $ 1 $ — $ 1 Interest cost 52 12 19 2 — 7 Expected return on plan assets (49) (19) (19) (1) — (4) Amortization: Prior service costs 2 3 — — — — Regulatory asset — — — — — 4 Net (gain)/loss (2) — 1 — — (2) Net periodic postretirement benefit cost $ 17 $ (1) $ 5 $ 2 $ — $ 6

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS As of September 30, 2020, 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: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Southern Company Assets: Energy-related derivatives (a) $ 488 $ 218 $ 117 $ — $ 823 Interest rate derivatives — 20 — — 20 Foreign currency derivatives — 29 — — 29 Investments in trusts: (b)(c) Domestic equity 754 137 — — 891 Foreign equity 71 220 — — 291 U.S. Treasury and government agency securities — 268 — — 268 Municipal bonds — 99 — — 99 Pooled funds – fixed income — 17 — — 17 Corporate bonds 15 376 — — 391 Mortgage and asset backed securities — 79 — — 79 Private equity — — — 68 68 Cash and cash equivalents 1 — — — 1 Other 25 6 — — 31 Cash equivalents 2,750 11 — — 2,761 Other investments 9 19 — — 28 Total $ 4,113 $ 1,499 $ 117 $ 68 $ 5,797 Liabilities: Energy-related derivatives (a) $ 521 $ 155 $ 75 $ — $ 751 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 19 — 19 Total $ 521 $ 178 $ 94 $ — $ 793 Fair Value Measurements Using: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Alabama Power Assets: Energy-related derivatives $ — $ 23 $ — $ — $ 23 Nuclear decommissioning trusts: (b) Domestic equity 477 128 — — 605 Foreign equity 71 64 — — 135 U.S. Treasury and government agency securities — 21 — — 21 Municipal bonds — 1 — — 1 Corporate bonds 15 159 — — 174 Mortgage and asset backed securities — 27 — — 27 Private equity — — — 68 68 Other 6 — — — 6 Cash equivalents 825 11 — — 836 Other investments — 19 — — 19 Total $ 1,394 $ 453 $ — $ 68 $ 1,915 Liabilities: Energy-related derivatives $ — $ 6 $ — $ — $ 6 Georgia Power Assets: Energy-related derivatives $ — $ 31 $ — $ — $ 31 Nuclear decommissioning trusts: (b)(c) Domestic equity 277 1 — — 278 Foreign equity — 153 — — 153 U.S. Treasury and government agency securities — 247 — — 247 Municipal bonds — 98 — — 98 Corporate bonds — 217 — — 217 Mortgage and asset backed securities — 52 — — 52 Other 19 6 — — 25 Cash equivalents 485 — — — 485 Total $ 781 $ 805 $ — $ — $ 1,586 Liabilities: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Fair Value Measurements Using: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Mississippi Power Assets: Energy-related derivatives $ — $ 18 $ — $ — $ 18 Cash equivalents 36 — — — 36 Total $ 36 $ 18 $ — $ — $ 54 Liabilities: Energy-related derivatives $ — $ 7 $ — $ — $ 7 Southern Power Assets: Energy-related derivatives $ — $ 5 $ — $ — $ 5 Foreign currency derivatives — 29 — — 29 Cash equivalents 149 — — — 149 Total $ 149 $ 34 $ — $ — $ 183 Liabilities: Energy-related derivatives $ — $ 1 $ — $ — $ 1 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 19 — 19 Total $ — $ 24 $ 19 $ — $ 43 Southern Company Gas Assets: Energy-related derivatives (a) $ 488 $ 141 $ 117 $ — $ 746 Non-qualified deferred compensation trusts: Domestic equity — 8 — — 8 Foreign equity — 3 — — 3 Pooled funds – fixed income — 17 — — 17 Cash equivalents 1 — — — 1 Cash equivalents and restricted cash 113 — — — 113 Total $ 602 $ 169 $ 117 $ — $ 888 Liabilities: Energy-related derivatives (a) $ 521 $ 132 $ 75 $ — $ 728 (a) Energy-related derivatives exclude cash collateral of $70 million. (b) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. (c) Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of September 30, 2020, approximately $25 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan to creditors under the funds' managers' securities lending program. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. Southern Company, Alabama Power, and Georgia Power continue to elect the option to fair value investment securities held in the nuclear decommissioning trust funds. The fair value of the funds, including reinvested interest and dividends and excluding the funds' expenses, increased (decreased) by the amounts shown in the table below for the three and nine months ended September 30, 2020 and 2019. The changes were recorded as a change to the regulatory assets and liabilities related to AROs for Georgia Power and Alabama Power, respectively. Fair value increases (decreases) Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) Southern Company $ 108 $ 27 $ 85 $ 255 Alabama Power 66 15 24 140 Georgia Power 42 12 61 115 Valuation Methodologies The energy-related derivatives primarily consist of exchange-traded and over-the-counter financial products for natural gas and physical power products, including, from time to time, basis swaps. These are standard products used within the energy industry and are valued using the market approach. The inputs used are mainly from observable market sources, such as forward natural gas prices, power prices, implied volatility, and overnight index swap interest rates. Interest rate derivatives are also standard over-the-counter products that are valued using observable market data and assumptions commonly used by market participants. The fair value of interest rate derivatives reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future interest rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and occasionally, implied volatility of interest rate options. The fair value of cross-currency swaps reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future foreign currency exchange rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and discount rates. The interest rate derivatives and cross-currency swaps are categorized as Level 2 under Fair Value Measurements as these inputs are based on observable data and valuations of similar instruments. See Note (J) for additional information on how these derivatives are used. For fair value measurements of the investments within the nuclear decommissioning trusts and the non-qualified deferred compensation trusts, external pricing vendors are designated for each asset class with each security specifically assigned a primary pricing source. For investments held within commingled funds, fair value is determined at the end of each business day through the net asset value, which is established by obtaining the underlying securities' individual prices from the primary pricing source. A market price secured from the primary source vendor is then evaluated by management in its valuation of the assets within the trusts. As a general approach, fixed income market pricing vendors gather market data (including indices and market research reports) and integrate relative credit information, observed market movements, and sector news into proprietary pricing models, pricing systems, and mathematical tools. Dealer quotes and other market information, including live trading levels and pricing analysts' judgments, are also obtained when available. The NRC requires licensees of commissioned nuclear power reactors to establish a plan for providing reasonable assurance of funds for future decommissioning. See Note 6 to the financial statements under "Nuclear Decommissioning" in Item 8 of the Form 10-K for additional information. Southern Power has contingent payment obligations related to certain acquisitions whereby Southern Power is primarily obligated to make generation-based payments to the seller, which commenced at the commercial operation of the respective facility and continue through 2026. The obligation is categorized as Level 3 under Fair Value Measurements as the fair value is determined using significant unobservable inputs for the forecasted facility generation in MW-hours, as well as other inputs such as a fixed dollar amount per MW-hour, and a discount rate. The fair value of contingent consideration reflects the net present value of expected payments and any periodic change arising from forecasted generation is expected to be immaterial. "Other investments" include investments traded in the open market that have maturities greater than 90 days, which are categorized as Level 2 under Fair Value Measurements and are comprised of corporate bonds, bank certificates of deposit, treasury bonds, and/or agency bonds. As of September 30, 2020, the fair value measurements of private equity investments held in Alabama Power's nuclear decommissioning trusts that are calculated at net asset value per share (or its equivalent) as a practical expedient totaled $68 million and unfunded commitments related to the private equity investments totaled $67 million. Private equity investments include high-quality private equity funds across several market sectors and funds that invest in real estate assets. Private equity funds do not have redemption rights. Distributions from these funds will be received as the underlying investments in the funds are liquidated. As of September 30, 2020, other financial instruments for which the carrying amount did not equal fair value were as follows: Southern Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (*) (in millions) Long-term debt, including securities due within one year: Carrying amount $ 49,743 $ 9,113 $ 12,700 $ 1,402 $ 4,155 $ 6,461 Fair value 56,739 10,741 15,052 1,562 4,535 7,640 (*) 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 lives of the respective bonds. The fair values are determined using Level 2 measurements and are based on quoted market prices for the same or similar issues or on the current rates available to the Registrants. Commodity Contracts with Level 3 Valuation Inputs As of September 30, 2020, the fair value of Southern Company Gas' Level 3 physical natural gas forward contracts was $42 million. Since commodity contracts classified as Level 3 typically include a combination of observable and unobservable components, the changes in fair value may include amounts due in part to observable market factors, or changes to assumptions on the unobservable components. The following table includes transfers to Level 3, which represent the fair value of Southern Company Gas' commodity derivative contracts that include a significant unobservable component for the first time during the period. Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 (in millions) Beginning balance $ 80 $ 14 Transfers to Level 3 — 70 Transfers from Level 3 (2) (5) Instruments realized or otherwise settled during period (9) (16) Changes in fair value (27) (21) Ending balance $ 42 $ 42 Changes in fair value of Level 3 instruments represent changes in gains and losses for the periods that are reported on Southern Company Gas' statements of income in natural gas revenues. The valuation of certain commodity contracts requires the use of certain unobservable inputs. All forward pricing used in the valuation of such contracts is directly based on third-party market data, such as broker quotes and exchange settlements, when that data is available. If third-party market data is not available, then industry standard methodologies are used to develop inputs that maximize the use of relevant observable inputs and minimize the use of unobservable inputs. Observable inputs, including some forward prices used for determining fair value, reflect the best available market information. Unobservable inputs are updated using industry standard techniques such as extrapolation, combining observable forward inputs supplemented by historical market and other relevant data. Level 3 physical natural gas forward contracts include unobservable forward price inputs (ranging from $(1.11) to $0.24 per mmBtu). Forward price increases (decreases) as of September 30, 2020 would have resulted in higher (lower) values on a net basis.

DERIVATIVES

DERIVATIVES	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	DERIVATIVES Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas are exposed to market risks, including commodity price risk, interest rate risk, weather risk, and occasionally foreign currency exchange rate risk. To manage the volatility attributable to these exposures, each company nets its exposures, where possible, to take advantage of natural offsets and enters into various derivative transactions for the remaining exposures pursuant to each company's policies in areas such as counterparty exposure and risk management practices. Southern Company Gas' wholesale gas operations use various contracts in its commercial activities that generally meet the definition of derivatives. For the traditional electric operating companies, Southern Power, and Southern Company Gas' other businesses, each company's policy is that derivatives are to be used primarily for hedging purposes and mandates strict adherence to all applicable risk management policies. Derivative positions are monitored using techniques including, but not limited to, market valuation, value at risk, stress testing, and sensitivity analysis. Derivative instruments are recognized at fair value in the balance sheets as either assets or liabilities and are presented on a net basis. See Note (I) for additional fair value information. In the statements of cash flows, any cash impacts of settled energy-related and interest rate derivatives are recorded as operating activities. Any cash impacts of settled foreign currency derivatives are classified as operating or financing activities to correspond with classification of the hedged interest or principal, respectively. See Note 1 to the financial statements under "Financial Instruments" in Item 8 of the Form 10-K for additional information. Energy-Related Derivatives The traditional electric operating companies, Southern Power, and Southern Company Gas enter into energy-related derivatives to hedge exposures to electricity, natural gas, and other fuel price changes. However, due to cost-based rate regulations and other various cost recovery mechanisms, the traditional electric operating companies and the natural gas distribution utilities have limited exposure to market volatility in energy-related commodity prices. Each of the traditional electric operating companies and certain of the natural gas distribution utilities of Southern Company Gas manage fuel-hedging programs, implemented per the guidelines of their respective state PSCs or other applicable state regulatory agencies, through the use of financial derivative contracts, which are expected to continue to mitigate price volatility. The traditional electric operating companies (with respect to wholesale generating capacity) and Southern Power have limited exposure to market volatility in energy-related commodity prices because their long-term sales contracts shift substantially all fuel cost responsibility to the purchaser. However, the traditional electric operating companies and Southern Power may be exposed to market volatility in energy-related commodity prices to the extent any uncontracted capacity is used to sell electricity. Southern Company Gas retains exposure to price changes that can, in a volatile energy market, be material and can adversely affect its results of operations. Southern Company Gas also enters into weather derivative contracts as economic hedges of operating margins in the event of warmer-than-normal weather. Exchange-traded options are carried at fair value, with changes reflected in operating revenues. Non-exchange-traded options are accounted for using the intrinsic value method. Changes in the intrinsic value for non-exchange-traded contracts are reflected in operating revenues. Energy-related derivative contracts are accounted for under one of three methods: • Regulatory Hedges — Energy-related derivative contracts designated as regulatory hedges relate primarily to the traditional electric operating companies' and the natural gas distribution utilities' fuel-hedging programs, where gains and losses are initially recorded as regulatory liabilities and assets, respectively, and then are included in fuel expense as the underlying fuel is used in operations and ultimately recovered through the respective fuel cost recovery clauses. • Cash Flow Hedges — Gains and losses on energy-related derivatives designated as cash flow hedges (which are mainly used to hedge anticipated purchases and sales) are initially deferred in accumulated OCI before being recognized in the statements of income in the same period and in the same income statement line item as the earnings effect of the hedged transactions. • Not Designated — Gains and losses on energy-related derivative contracts that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. Some energy-related derivative contracts require physical delivery as opposed to financial settlement, and this type of derivative is both common and prevalent within the electric and natural gas industries. When an energy-related derivative contract is settled physically, any cumulative unrealized gain or loss is reversed and the contract price is recognized in the respective line item representing the actual price of the underlying goods being delivered. At September 30, 2020, the net volume of energy-related derivative contracts for natural gas positions, together with the longest hedge date over which the respective entity is hedging its exposure to the variability in future cash flows for forecasted transactions and the longest non-hedge date for derivatives not designated as hedges, were as follows: Net Longest Longest (in millions) Southern Company (*) 877 2024 2031 Alabama Power 78 2024 — Georgia Power 131 2023 — Mississippi Power 86 2024 — Southern Power 14 2022 2021 Southern Company Gas (*) 568 2023 2031 (*) Southern Company Gas' derivative instruments include both long and short natural gas positions. A long position is a contract to purchase natural gas and a short position is a contract to sell natural gas. Southern Company Gas' volume represents the net of long natural gas positions of 4.6 billion mmBtu and short natural gas positions of 4.1 billion mmBtu as of September 30, 2020, which is also included in Southern Company's total volume. At September 30, 2020, the net volume of Southern Power's energy-related derivative contracts for power to be sold was 1 million MWHs, all of which expire in 2021. In addition to the volumes discussed above, the traditional electric operating companies and Southern Power enter into physical natural gas supply contracts that provide the option to sell back excess natural gas due to operational constraints. The maximum expected volume of natural gas subject to such a feature is 12 million mmBtu for Southern Company, which includes 3 million mmBtu for Alabama Power, 4 million mmBtu for Georgia Power, 1 million mmBtu for Mississippi Power, and 4 million mmBtu for Southern Power. For cash flow hedges of energy-related derivatives, the estimated pre-tax gains (losses) expected to be reclassified from accumulated OCI to earnings for the 12-month period ending September 30, 2021 are immaterial for all Registrants. Interest Rate Derivatives Southern Company and certain subsidiaries may enter into interest rate derivatives to hedge exposure to changes in interest rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. Derivatives related to existing variable rate securities or forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and presented on the same income statement line item as the earnings effect of the hedged transactions. Derivatives related to existing fixed rate securities are accounted for as fair value hedges, where the derivatives' fair value gains or losses and hedged items' fair value gains or losses are both recorded directly to earnings on the same income statement line item. Fair value gains or losses on derivatives that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. At September 30, 2020, the following interest rate derivatives were outstanding: Notional Interest Weighted Hedge Fair Value Gain (Loss) at September 30, 2020 (in millions) (in millions) Cash Flow Hedges of Existing Debt Mississippi Power $ 60 1-month LIBOR 0.58% December 2021 $ — Fair Value Hedges of Existing Debt Southern Company parent 1,500 2.35% 1-month LIBOR + 0.87% July 2021 20 Southern Company $ 1,560 $ 20 For cash flow hedge interest rate derivatives, the estimated pre-tax gains (losses) expected to be reclassified from accumulated OCI to interest expense for the 12-month period ending September 30, 2021 total $(25) million for Southern Company and are immaterial for all other Registrants. Deferred gains and losses related to interest rate derivatives are expected to be amortized into earnings through 2046 for the Southern Company parent entity, 2035 for Alabama Power, 2044 for Georgia Power, 2028 for Mississippi Power, and 2046 for Southern Company Gas. Foreign Currency Derivatives Southern Company and certain subsidiaries, including Southern Power, may enter into foreign currency derivatives to hedge exposure to changes in foreign currency exchange rates, such as that arising from the issuance of debt denominated in a currency other than U.S. dollars. Derivatives related to forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and on the same income statement line as the earnings effect of the hedged transactions, including foreign currency gains or losses arising from changes in the U.S. currency exchange rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. At September 30, 2020, the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at September 30, 2020 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ 11 Southern Power 564 3.78% 500 1.85% June 2026 (5) Total $ 1,241 € 1,100 $ 6 The estimated pre-tax gains (losses) related to Southern Power's foreign currency derivatives expected to be reclassified from accumulated OCI to earnings for the 12-month period ending September 30, 2021 are $(14) million. Derivative Financial Statement Presentation and Amounts Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas enter into derivative contracts that may contain certain provisions that permit intra-contract netting of derivative receivables and payables for routine billing and offsets related to events of default and settlements. Southern Company and certain subsidiaries also utilize master netting agreements to mitigate exposure to counterparty credit risk. These agreements may contain provisions that permit netting across product lines and against cash collateral. The fair value amounts of derivative assets and liabilities on the balance sheet are presented net to the extent that there are netting arrangements or similar agreements with the counterparties. The fair value of energy-related derivatives, interest rate derivatives, and foreign currency derivatives was reflected in the balance sheets as follows: As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Southern Company Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 52 $ 13 $ 3 $ 70 Other deferred charges and assets/Other deferred credits and liabilities 30 15 6 44 Total derivatives designated as hedging instruments for regulatory purposes $ 82 $ 28 $ 9 $ 114 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 8 $ 3 $ 1 $ 6 Other deferred charges and assets/Other deferred credits and liabilities 2 — — — Interest rate derivatives: Other current assets/Other current liabilities 19 — 2 23 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 24 Other deferred charges and assets/Other deferred credits and liabilities 29 — 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 58 $ 26 $ 19 $ 54 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 392 $ 428 $ 461 $ 358 Other deferred charges and assets/Other deferred credits and liabilities 338 291 207 225 Total derivatives not designated as hedging instruments $ 730 $ 719 $ 668 $ 583 Gross amounts recognized $ 870 $ 773 $ 696 $ 751 Gross amounts offset (a) (636) (706) (463) (562) Net amounts recognized in the Balance Sheets (b) $ 234 $ 67 $ 233 $ 189 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Alabama Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 14 $ 2 $ 2 $ 14 Other deferred charges and assets/Other deferred credits and liabilities 9 4 2 10 Total derivatives designated as hedging instruments for regulatory purposes $ 23 $ 6 $ 4 $ 24 Gross amounts recognized $ 23 $ 6 $ 4 $ 24 Gross amounts offset (5) (5) (2) (2) Net amounts recognized in the Balance Sheets $ 18 $ 1 $ 2 $ 22 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 18 $ 3 $ 1 $ 32 Other deferred charges and assets/Other deferred credits and liabilities 13 6 3 21 Total derivatives designated as hedging instruments for regulatory purposes $ 31 $ 9 $ 4 $ 53 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ — $ — $ — $ 17 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ — $ — $ 17 Gross amounts recognized $ 31 $ 9 $ 4 $ 70 Gross amounts offset (9) (9) (3) (3) Net amounts recognized in the Balance Sheets $ 22 $ — $ 1 $ 67 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Mississippi Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 10 $ 2 $ — $ 15 Other deferred charges and assets/Other deferred credits and liabilities 8 5 1 12 Total derivatives designated as hedging instruments for regulatory purposes $ 18 $ 7 $ 1 $ 27 Gross amounts recognized $ 18 $ 7 $ 1 $ 27 Gross amounts offset (7) (7) (1) (1) Net amounts recognized in the Balance Sheets $ 11 $ — $ — $ 26 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 4 $ 1 $ 1 $ 2 Other deferred charges and assets/Other deferred credits and liabilities 1 — — — Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 24 Other deferred charges and assets/Other deferred credits and liabilities 29 — 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 34 $ 24 $ 17 $ 26 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ — $ — $ 2 $ 1 Total derivatives not designated as hedging instruments $ — $ — $ 2 $ 1 Gross amounts recognized $ 34 $ 24 $ 19 $ 27 Gross amounts offset (1) (1) — — Net amounts recognized in the Balance Sheets $ 33 $ 23 $ 19 $ 27 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Southern Company Gas Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 10 $ 6 $ — $ 9 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 10 $ 6 $ — $ 10 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 4 $ 2 $ — $ 4 Other deferred charges and assets/Other deferred credits and liabilities 1 — — — Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — — 2 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 5 $ 2 $ 2 $ 4 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 392 $ 428 $ 459 $ 357 Other deferred charges and assets/Other deferred credits and liabilities 338 291 207 225 Total derivatives not designated as hedging instruments $ 730 $ 719 $ 666 $ 582 Gross amounts of recognized $ 745 $ 727 $ 668 $ 596 Gross amounts offset (a) (614) (684) (456) (555) Net amounts recognized in the Balance Sheets (b) $ 131 $ 43 $ 212 $ 41 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $70 million and $99 million as of September 30, 2020 and December 31, 2019, respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $3 million and $4 million as of September 30, 2020 and December 31, 2019, respectively. The traditional electric operating companies had no energy-related derivatives not designated as hedging instruments at September 30, 2020 and immaterial amounts at December 31, 2019. At September 30, 2020 and December 31, 2019, the pre-tax effects of unrealized derivative gains (losses) arising from energy-related derivative instruments designated as regulatory hedging instruments and deferred were as follows: Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet Derivative Category and Balance Sheet Southern Alabama Georgia Mississippi Southern Company Gas (in millions) At September 30, 2020: Energy-related derivatives: Other regulatory assets, current $ (5) $ — $ — $ — $ (5) Other regulatory liabilities, current 41 12 15 8 6 Other regulatory liabilities, deferred 15 5 7 3 — Total energy-related derivative gains (losses) $ 51 $ 17 $ 22 $ 11 $ 1 At December 31, 2019: Energy-related derivatives: Other regulatory assets, current $ (63) $ (14) $ (31) $ (15) $ (3) Other regulatory assets, deferred (37) (8) (18) (11) — Other regulatory liabilities, current 6 2 — — 4 Total energy-related derivative gains (losses) $ (94) $ (20) $ (49) $ (26) $ 1 For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of cash flow hedge accounting on accumulated OCI were as follows: Gain (Loss) Recognized in OCI on Derivative For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 (in millions) (in millions) Southern Company Energy-related derivatives $ 9 $ (5) $ 2 $ (11) Interest rate derivatives 1 (52) (27) (88) Foreign currency derivatives 54 (68) (10) (107) Total $ 64 $ (125) $ (35) $ (206) Georgia Power Interest rate derivatives $ — $ (47) $ (3) $ (83) Southern Power Energy-related derivatives $ 5 $ (3) $ 2 $ (5) Foreign currency derivatives 54 (68) (10) (107) Total $ 59 $ (71) $ (8) $ (112) Southern Company Gas Energy-related derivatives $ 4 $ (2) $ — $ (6) Interest rate derivatives 1 (5) (24) (5) Total $ 5 $ (7) $ (24) $ (11) For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of energy-related derivatives and interest rate derivatives designated as cash flow hedging instruments on accumulated OCI were immaterial for the other Registrants. For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of cash flow and fair value hedge accounting on income were as follows: Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 (in millions) (in millions) Southern Company Total cost of natural gas $ 71 $ 79 $ 654 $ 956 Gain (loss) on energy-related cash flow hedges (a) — — (8) — Total depreciation and amortization 889 760 2,619 2,267 Gain (loss) on energy-related cash flow hedges (a) (1) (1) (3) (5) Total interest expense, net of amounts capitalized (443) (434) (1,343) (1,294) Gain (loss) on interest rate cash flow hedges (a) (6) (5) (19) (14) Gain (loss) on foreign currency cash flow hedges (a) (6) (6) (18) (18) Gain (loss) on interest rate fair value hedges (b) (3) 10 27 43 Total other income (expense), net 113 61 319 239 Gain (loss) on foreign currency cash flow hedges (a)(c) 56 (54) 52 (62) Southern Power Total depreciation and amortization $ 129 $ 120 $ 367 $ 357 Gain (loss) on energy-related cash flow hedges (a) (1) (1) (3) (5) Total interest expense, net of amounts capitalized (36) (43) (114) (127) Gain (loss) on foreign currency cash flow hedges (a) (6) (6) (18) (18) Total other income (expense), net 13 6 19 48 Gain (loss) on foreign currency cash flow hedges (a)(c) 56 (54) 52 (62) (a) Reclassified from accumulated OCI into earnings. (b) For fair value hedges, changes in the fair value of the derivative contracts are generally equal to changes in the fair value of the underlying debt and have no material impact on income. (c) The reclassification from accumulated OCI into other income (expense), net completely offsets currency gains and losses arising from changes in the U.S. currency exchange rates used to record the euro-denominated notes. For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of cash flow and fair value hedge accounting on income for energy-related derivatives and interest rate derivatives were immaterial for the traditional electric operating companies and Southern Company Gas. As of September 30, 2020 and December 31, 2019, the following amounts were recorded on the balance sheets related to cumulative basis adjustments for fair value hedges: Carrying Amount of the Hedged Item Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item Balance Sheet Location of Hedged Items As of September 30, 2020 As of December 31, 2019 As of September 30, 2020 As of December 31, 2019 (in millions) (in millions) Southern Company Securities due within one year $ (1,513) $ (599) $ (15) $ — Long-term debt — (1,494) — 3 For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of energy-related derivatives not designated as hedging instruments on the statements of income of Southern Company and Southern Company Gas were as follows: Gain (Loss) Three Months Ended September 30, Nine Months Ended September 30, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2020 2019 2020 2019 (in millions) (in millions) Energy-related derivatives: Natural gas revenues (*) $ (30) $ (2) $ 54 $ 81 Cost of natural gas 5 2 18 5 Total derivatives in non-designated hedging relationships $ (25) $ — $ 72 $ 86 (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented. For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of energy-related derivatives not designated as hedging instruments were immaterial for all other Registrants. Contingent Features Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas do not have any credit arrangements that would require material changes in payment schedules or terminations as a result of a credit rating downgrade. There are certain derivatives that could require collateral, but not accelerated payment, in the event of various credit rating changes of certain Southern Company subsidiaries. At September 30, 2020, the Registrants had no collateral posted with derivative counterparties to satisfy these arrangements. For the Registrants with interest rate derivatives at September 30, 2020, the fair value of interest rate derivative liabilities with contingent features and the maximum potential collateral requirements arising from the credit-risk-related contingent features, at a rating below BBB- and/or Baa3, was immaterial. At September 30, 2020, the fair value of energy-related derivative liabilities with contingent features and the maximum potential collateral requirements arising from the credit-risk-related contingent features, at a rating below BBB- and/or Baa3, were immaterial for all Registrants. The maximum potential collateral requirements arising from the credit-risk-related contingent features for the traditional electric operating companies and Southern Power include certain agreements that could require collateral in the event that one or more Southern Company power pool participants has a credit rating change to below investment grade. Following the sale of Gulf Power to NextEra Energy, Gulf Power is continuing to participate in the Southern Company power pool for a defined transition period that, subject to certain potential adjustments, is scheduled to end on January 1, 2024. Generally, collateral may be provided by a Southern Company guaranty, letter of credit, or cash. If collateral is required, fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral are not offset against fair value amounts recognized for derivatives executed with the same counterparty. Alabama Power and Southern Power maintain accounts with certain regional transmission organizations to facilitate financial derivative transactions. Based on the value of the positions in these accounts and the associated margin requirements, Alabama Power and Southern Power may be required to post collateral. At September 30, 2020, cash collateral posted in these accounts was immaterial. Southern Company Gas maintains accounts with brokers or the clearing houses of certain exchanges to facilitate financial derivative transactions. Based on the value of the positions in these accounts and the associated margin requirements, Southern Company Gas may be required to deposit cash into these accounts. At September 30, 2020, cash collateral held on deposit in broker margin accounts was $70 million. The Registrants are exposed to losses related to financial instruments in the event of counterparties' nonperformance. The Registrants only enter into agreements and material transactions with counterparties that have investment grade credit ratings by Moody's and S&P or with counterparties who have posted collateral to cover potential credit exposure. The Registrants have also established risk management policies and controls to determine and monitor the creditworthiness of counterparties in order to mitigate their exposure to counterparty credit risk. Prior to entering into a physical transaction, Southern Company Gas assigns physical wholesale counterparties an internal credit rating and credit limit based on the counterparties' Moody's, S&P, and Fitch ratings, commercially available credit reports, and audited financial statements. Southern Company Gas may require counterparties to pledge additional collateral when deemed necessary. In addition, Southern Company Gas conducts credit evaluations and obtains appropriate internal approvals for the counterparty's line of credit before any transaction with the counterparty is executed. In most cases, the counterparty must have an investment grade rating, which includes a minimum long-term debt rating of Baa3 from Moody's and BBB- from S&P. Generally, Southern Company Gas requires credit enhancements by way of a guaranty, cash deposit, or letter of credit for transaction counterparties that do not have investment grade ratings. Southern Company Gas also utilizes master netting agreements whenever possible to mitigate exposure to counterparty credit risk. When Southern Company Gas is engaged in more than one outstanding derivative transaction with the same counterparty and it also has a legally enforceable netting agreement with that counterparty, the "net" mark-to-market exposure represents the netting of the positive and negative exposures with that counterparty and a reasonable measure of Southern Company Gas' credit risk. Southern Company Gas also uses other netting agreements with certain counterparties with whom it conducts significant transactions. Master netting agreements enable Southern Company Gas to net certain assets and liabilities by counterparty. Southern Company Gas also nets across product lines and against cash collateral provided the master netting and cash collateral agreements include such provisions. Southern Company Gas may require counterparties to pledge additional collateral when deemed necessary. The Registrants do not anticipate a material adverse effect on their respective financial statements as a result of counterparty nonperformance.

ACQUISITIONS AND DISPOSITIONS

ACQUISITIONS AND DISPOSITIONS	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
ACQUISITIONS AND DISPOSITIONS	ACQUISITIONS AND DISPOSITIONSSee Note 15 to the financial statements in Item 8 of the Form 10-K for additional information, including details of assets and liabilities held for sale at December 31, 2019 for Southern Company, Southern Power, and Southern Company Gas. The Registrants had no material assets or liabilities held for sale at September 30, 2020. Southern Power Asset Acquisitions During the nine months ended September 30, 2020, Southern Power acquired a controlling interest in the wind facility listed below. Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller Approximate Nameplate Capacity ( MW ) Location Southern Power COD PPA Contract Period Beech Ridge II Wind Invenergy Renewables LLC 56 Greenbrier County, 100% of Class A (*) May 2020 12 years (*) In May 2020, Southern Power purchased 100% of the Class A membership interests and now owns the controlling interest in the project, with the Class B member, Invenergy Renewables LLC, owning the noncontrolling interest. In March 2020, Southern Power entered into an agreement to acquire a controlling membership interest in an approximately 300-MW wind facility located in South Dakota. The acquisition is subject to FERC approval and certain other customary conditions to closing, including commercial operation of the facility, which is expected to occur in the first quarter 2021. The facility's output is contracted under two long-term PPAs. The ultimate outcome of this matter cannot be determined at this time. Construction Projects During the nine months ended September 30, 2020, Southern Power completed construction of and placed in service the Reading wind facility, continued construction of the Skookumchuck wind facility, and commenced construction of the Garland and Tranquillity battery energy storage facilities. Total aggregate construction costs, excluding acquisition costs, are expected to be between $475 million and $545 million for the facilities under construction. At September 30, 2020, total costs of construction incurred for these projects were $244 million and are included in CWIP. The ultimate outcome of these matters cannot be determined at this time. Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Nine Months Ended September 30, 2020 Reading (a) Wind 200 Osage and Lyon Counties, KS May 2020 12 years Projects Under Construction as of September 30, 2020 Skookumchuck (b) Wind 136 Lewis and Thurston Counties, WA November 2020 20 years Garland Solar Storage (c) Battery energy storage system 88 Kern County, CA Second quarter 2021 20 years Tranquillity Solar Storage (c) Battery energy storage system 72 Fresno County, CA Second quarter 2021 20 years (a) In 2018, Southern Power purchased 100% of the membership interests of the Reading facility pursuant to a joint development arrangement. At the time the facility was placed in service, Southern Power recorded an operating lease right-of-use asset and an operating lease liability, each in the amount of $24 million. In June 2020, Southern Power completed a tax equity transaction whereby it received $156 million and now owns 100% of the Class B membership interests. (b) In October 2019, Southern Power purchased 100% of the membership interests of the Skookumchuck facility pursuant to a joint development arrangement. Southern Power expects to complete a tax equity transaction upon commercial operation and retain the Class B membership interests. Shortly after the completed tax equity transaction, Southern Power may sell a noncontrolling interest in these Class B membership interests to another partner. Southern Power would retain the controlling ownership interest in the facility. The ultimate outcome of these matters cannot be determined at this time. (c) Prior to commercial operation, Southern Power may enter into one or more partnerships, in which case it would ultimately own less than 100% of the Class B membership interests, but would retain ownership of the controlling interest. The ultimate outcome of this matter cannot be determined at this time. Development Projects Southern Power continues to evaluate and refine the deployment of the remaining wind turbine equipment purchased in 2016 and 2017 to development and construction projects. During the nine months ended September 30, 2020, certain wind turbine equipment was sold, resulting in an immaterial gain. Sales of Natural Gas and Biomass Plants On January 17, 2020, Southern Power completed the sale of its equity interests in Plant Mankato (including the 385-MW expansion unit completed in May 2019) to a subsidiary of Xcel for a purchase price of approximately $663 million, including final working capital adjustments. The sale resulted in a gain of approximately $39 million ($23 million after tax). The assets and liabilities of Plant Mankato were classified as held for sale on Southern Company's and Southern Power's balance sheets at December 31, 2019. Plants Nacogdoches (sold in June 2019) and Mankato represented individually significant components of Southern Power; therefore, pre-tax income for these components for the three months ended September 30, 2019 and the nine months ended September 30, 2020 and 2019 is presented below: Three Months Ended Nine Months Ended September 30, 2020 2019 (in millions) Southern Power's earnings before income taxes: (*) Plant Nacogdoches $ — N/A $ 16 Plant Mankato $ 12 $ 2 $ 20 (*) Earnings before income taxes for components reflect the cessation of depreciation and amortization on the long-lived assets being sold upon classification as held for sale in November 2018 and April 2019 for Plant Mankato and Plant Nacogdoches, respectively. Southern Company Gas On March 24, 2020, Southern Company Gas completed the sale of its interests in Pivotal LNG and Atlantic Coast Pipeline to Dominion Modular LNG Holdings, Inc. and Dominion Atlantic Coast Pipeline, LLC, respectively, with aggregate proceeds of $178 million, including working capital adjustments. The loss associated with the transactions was immaterial. Southern Company Gas also expects to receive payments in February 2021 and September 2021 of $5 million each contingent upon Dominion Modular LNG Holdings, Inc. meeting certain milestones related to Pivotal LNG. The assets and liabilities of Pivotal LNG and the interest in Atlantic Coast Pipeline were classified as held for sale at December 31, 2019. See Notes 3 and 7 under "Other Matters – Southern Company Gas – Gas Pipeline Projects" and "Southern Company Gas – Equity Method Investments," respectively, in Item 8 of the Form 10-K and Notes (C) and (E) under "Other Matters – Southern Company Gas" and "Southern Company Gas," respectively.

SEGMENT AND RELATED INFORMATION

SEGMENT AND RELATED INFORMATION	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
SEGMENT AND RELATED INFORMATION	SEGMENT AND RELATED INFORMATION Southern Company The primary businesses of the Southern Company system are electricity sales by the traditional electric operating companies and Southern Power and the distribution of natural gas by Southern Company Gas. The traditional electric operating companies – Alabama Power, Georgia Power, and Mississippi Power – are vertically integrated utilities providing electric service in three Southeastern states. Southern Power develops, constructs, acquires, owns, and manages power generation assets, including renewable energy projects, and sells electricity at market-based rates in the wholesale market. Southern Company Gas distributes natural gas through its natural gas distribution utilities and is involved in several other complementary businesses including gas pipeline investments, wholesale gas services, and gas marketing services. Financial data for business segments and products and services for the three and nine months ended September 30, 2020 and 2019 was as follows: Electric Utilities Traditional Southern Eliminations Total Southern Company Gas All Eliminations Consolidated (in millions) Three Months Ended September 30, 2020 Operating revenues $ 4,629 $ 523 $ (103) $ 5,049 $ 477 $ 132 $ (38) $ 5,620 Segment net income (loss) (a) 1,284 74 — 1,358 14 (122) 1 1,251 Nine Months Ended September 30, 2020 Operating revenues $ 11,576 $ 1,337 $ (285) $ 12,628 $ 2,362 $ 380 $ (112) $ 15,258 Segment net income (loss) (a)(b)(c)(d) 2,571 212 — 2,783 360 (420) 9 2,732 At September 30, 2020 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 85,218 13,424 (671) 97,971 21,932 4,116 (861) 123,158 Three Months Ended September 30, 2019 Operating revenues $ 4,908 $ 574 $ (119) $ 5,363 $ 498 $ 146 $ (12) $ 5,995 Segment net income (loss) (a)(e)(f) 1,373 86 — 1,459 (29) (110) (4) 1,316 Nine Months Ended September 30, 2019 Operating revenues $ 12,252 $ 1,527 $ (331) $ 13,448 $ 2,661 $ 514 $ (118) $ 16,505 Segment net income (loss) (a)(e)(f)(g) 2,719 316 — 3,035 347 931 (15) 4,298 At December 31, 2019 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 81,063 14,300 (713) 94,650 21,687 3,511 (1,148) 118,700 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes a pre-tax charge of $149 million ($111 million after tax) related to Plant Vogtle Units 3 and 4. See Note (B) under "Georgia Power – Nuclear Construction" for additional information. (c) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $154 million ($74 million after tax) related to a leveraged lease investment. See Note (C) under "Other Matters – Southern Company" for additional information. (d) Segment net income (loss) for Southern Power includes a $39 million pre-tax gain ($23 million gain after tax) on the sale of Plant Mankato. See Note (K) under "Southern Power" for additional information. (e) Segment net income (loss) for Southern Company Gas includes a pre-tax impairment charge of $92 million ($65 million after tax) related to a natural gas storage facility in Louisiana. See Note 3 to the financial statements under "Other Matters – Southern Company Gas – Natural Gas Storage Facilities" in Item 8 of the Form 10-K for additional information. (f) Segment net income (loss) for the "All Other" column includes the preliminary pre-tax gain associated with the sale of Gulf Power of $2.5 billion ($1.3 billion after tax) for the nine months ended September 30, 2019, as well as impairment charges in contemplation of the sales of two of PowerSecure's business units totaling $18 million and $50 million for the three and nine months ended September 30, 2019, respectively. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company" for additional information. (g) Segment net income (loss) for Southern Power includes a $23 million pre-tax gain ($88 million gain after tax) on the sale of Plant Nacogdoches. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Power – Sale of Natural Gas and Biomass Plants" for additional information. Products and Services Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended September 30, 2020 $ 4,243 $ 584 $ 222 $ 5,049 Three Months Ended September 30, 2019 4,512 625 226 5,363 Nine Months Ended September 30, 2020 $ 10,503 $ 1,473 $ 652 $ 12,628 Nine Months Ended September 30, 2019 11,136 1,667 645 13,448 Southern Company Gas' Revenues Gas Wholesale Gas Services (*) Gas Other Total (in millions) Three Months Ended September 30, 2020 $ 476 $ (51) $ 39 $ 13 $ 477 Three Months Ended September 30, 2019 445 (2) 39 16 498 Nine Months Ended September 30, 2020 $ 2,072 $ (19) $ 272 $ 37 $ 2,362 Nine Months Ended September 30, 2019 2,169 132 326 34 2,661 (*) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. See "Southern Company Gas" herein for additional information. Southern Company Gas Southern Company Gas manages its business through four reportable segments – gas distribution operations, gas pipeline investments, wholesale gas services, and gas marketing services. The non-reportable segments are combined and presented as all other. Gas distribution operations is the largest component of Southern Company Gas' business and includes natural gas local distribution utilities that construct, manage, and maintain intrastate natural gas pipelines and gas distribution facilities in four states. Gas pipeline investments consists of joint ventures in natural gas pipeline investments including a 50% interest in SNG, a 20% ownership interest in the PennEast Pipeline construction project, a 50% joint ownership interest in the Dalton Pipeline, and a 5% ownership interest in the Atlantic Coast Pipeline construction project through its sale on March 24, 2020. These natural gas pipelines enable the provision of diverse sources of natural gas supplies to the customers of Southern Company Gas. Wholesale gas services provides natural gas asset management and/or related logistics services for each of Southern Company Gas' utilities except Nicor Gas as well as for non-affiliated companies. Additionally, wholesale gas services engages in natural gas storage and gas pipeline arbitrage and related activities. Gas marketing services provides natural gas marketing to end-use customers primarily in Georgia, Illinois, and Ohio through SouthStar. The all other column includes segments below the quantitative threshold for separate disclosure, including natural gas storage businesses, fuels operations through the sale of Southern Company Gas' interest in Pivotal LNG on March 24, 2020, the investment in Triton through its sale on May 29, 2019, and other subsidiaries that fall below the quantitative threshold for separate disclosure. See Notes (E) and (K) under "Southern Company Gas" for additional information. Business segment financial data for the three and nine months ended September 30, 2020 and 2019 was as follows: Gas Distribution Operations Gas Pipeline Investments Wholesale Gas Services (a) Gas Marketing Services Total All Other (b) Eliminations Consolidated (in millions) Three Months Ended September 30, 2020 Operating revenues $ 479 $ 8 $ (51) $ 39 $ 475 $ 8 $ (6) $ 477 Segment net income (loss) 46 23 (45) (3) 21 (7) — 14 Nine Months Ended September 30, 2020 Operating revenues $ 2,086 $ 24 $ (19) $ 272 $ 2,363 $ 24 $ (25) $ 2,362 Segment net income (loss) 284 74 (45) 59 372 (12) — 360 Total assets at September 30, 2020 18,715 1,609 650 1,461 22,435 10,979 (11,482) 21,932 Three Months Ended September 30, 2019 Operating revenues $ 448 $ 8 $ (2) $ 39 $ 493 $ 10 $ (5) $ 498 Segment net income (loss) 37 6 (9) (4) 30 (59) — (29) Nine Months Ended September 30, 2019 Operating revenues $ 2,188 $ 24 $ 132 $ 326 $ 2,670 $ 34 $ (43) $ 2,661 Segment net income (loss) 228 63 61 54 406 (59) — 347 Total assets at December 31, 2019 18,204 1,678 850 1,496 22,228 10,759 (11,300) 21,687 (a) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. A reconciliation of operating revenues and intercompany revenues is shown in the following table. Third Party Gross Revenues Intercompany Revenues Total Gross Revenues Less Gross Gas Costs Operating Revenues (in millions) Three Months Ended September 30, 2020 $ 1,050 $ 33 $ 1,083 $ 1,134 $ (51) Three Months Ended September 30, 2019 1,138 72 1,210 1,212 (2) Nine Months Ended September 30, 2020 $ 3,089 $ 81 $ 3,170 $ 3,189 $ (19) Nine Months Ended September 30, 2019 4,287 223 4,510 4,378 132 (b) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $92 million ($65 million after tax) for the three and nine months ended September 30, 2019 related to a natural gas storage facility in Louisiana. See Note 3 to the financial statements under "Other Matters – Southern Company Gas – Natural Gas Storage Facilities" in Item 8 of the Form 10-K for additional information.

INTRODUCTION (Policies)

INTRODUCTION (Policies)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting	The condensed quarterly financial statements of each Registrant included herein have been prepared by such Registrant, without audit, pursuant to the rules and regulations of the SEC. The Condensed Balance Sheets as of December 31, 2019 have been derived from the audited financial statements of each Registrant. In the opinion of each Registrant's management, the information regarding such Registrant furnished herein reflects all adjustments, which, except as otherwise disclosed, are of a normal recurring nature, necessary to present fairly the results of operations for the periods ended September 30, 2020 and 2019. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations, although each Registrant believes that the disclosures regarding such Registrant are adequate to make the information presented not misleading. Disclosures which would substantially duplicate the disclosures in the Form 10-K and details which have not changed significantly in amount or composition since the filing of the Form 10-K are generally omitted from this Quarterly Report on Form 10-Q unless specifically required by GAAP. Therefore, these Condensed Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the Form 10-K. Due to the seasonal variations in the demand for energy and other factors, including the impacts of the COVID-19 pandemic, operating results for the periods presented are not necessarily indicative of the operating results to be expected for the full year.
Reclassifications	Certain prior year data presented in the financial statements have been reclassified to conform to the current year presentation. These reclassifications had no impact on the overall results of operations, financial position, or cash flows of any Registrant.
Goodwill and Other Intangible Assets	Goodwill is not amortized but is subject to an annual impairment test in the fourth quarter of the year and on an interim basis as events and changes in circumstances occur, including, but not limited to, a significant change in operating performance, the business climate, legal or regulatory factors, or a planned sale or disposition of a significant portion of the business. The continued COVID-19 pandemic and related responses continue to disrupt supply chains, reduce labor availability and productivity, and reduce economic activity. These effects could have a variety of adverse impacts on Southern Company and its subsidiaries, including the $263 million of goodwill recorded at PowerSecure. If the impact of the COVID-19 pandemic becomes significant to the operating results of PowerSecure and its businesses, a portion of the associated goodwill may become impaired. The ultimate outcome of this matter cannot be determined at this time.
Natural Gas For Sale	Southern Company Gas, with the exception of Nicor Gas, carries natural gas inventory on a WACOG basis. For any declines in market prices below the WACOG considered to be other than temporary, an adjustment is recorded to reduce the value of natural gas inventories to market value. Nicor Gas' natural gas inventory is carried at cost on a LIFO basis. Inventory decrements occurring during the year that are restored prior to year end are charged to cost of natural gas at the estimated annual replacement cost. Inventory decrements that are not restored prior to year end are charged to cost of natural gas at the actual LIFO cost of the inventory layers liquidated. Southern Company Gas recorded no material adjustments to natural gas inventories for the three and nine months ended September 30, 2020 or the three months ended September 30, 2019 and recorded an adjustment of $10
Valuation Methodologies	Valuation Methodologies The energy-related derivatives primarily consist of exchange-traded and over-the-counter financial products for natural gas and physical power products, including, from time to time, basis swaps. These are standard products used within the energy industry and are valued using the market approach. The inputs used are mainly from observable market sources, such as forward natural gas prices, power prices, implied volatility, and overnight index swap interest rates. Interest rate derivatives are also standard over-the-counter products that are valued using observable market data and assumptions commonly used by market participants. The fair value of interest rate derivatives reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future interest rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and occasionally, implied volatility of interest rate options. The fair value of cross-currency swaps reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future foreign currency exchange rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and discount rates. The interest rate derivatives and cross-currency swaps are categorized as Level 2 under Fair Value Measurements as these inputs are based on observable data and valuations of similar instruments. See Note (J) for additional information on how these derivatives are used. For fair value measurements of the investments within the nuclear decommissioning trusts and the non-qualified deferred compensation trusts, external pricing vendors are designated for each asset class with each security specifically assigned a primary pricing source. For investments held within commingled funds, fair value is determined at the end of each business day through the net asset value, which is established by obtaining the underlying securities' individual prices from the primary pricing source. A market price secured from the primary source vendor is then evaluated by management in its valuation of the assets within the trusts. As a general approach, fixed income market pricing vendors gather market data (including indices and market research reports) and integrate relative credit information, observed market movements, and sector news into proprietary pricing models, pricing systems, and mathematical tools. Dealer quotes and other market information, including live trading levels and pricing analysts' judgments, are also obtained when available. The NRC requires licensees of commissioned nuclear power reactors to establish a plan for providing reasonable assurance of funds for future decommissioning. See Note 6 to the financial statements under "Nuclear Decommissioning" in Item 8 of the Form 10-K for additional information.
Derivatives	Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas are exposed to market risks, including commodity price risk, interest rate risk, weather risk, and occasionally foreign currency exchange rate risk. To manage the volatility attributable to these exposures, each company nets its exposures, where possible, to take advantage of natural offsets and enters into various derivative transactions for the remaining exposures pursuant to each company's policies in areas such as counterparty exposure and risk management practices. Southern Company Gas' wholesale gas operations use various contracts in its commercial activities that generally meet the definition of derivatives. For the traditional electric operating companies, Southern Power, and Southern Company Gas' other businesses, each company's policy is that derivatives are to be used primarily for hedging purposes and mandates strict adherence to all applicable risk management policies. Derivative positions are monitored using techniques including, but not limited to, market valuation, value at risk, stress testing, and sensitivity analysis. Derivative instruments are recognized at fair value in the balance sheets as either assets or liabilities and are presented on a net basis. See Note (I) for additional fair value information. In the statements of cash flows, any cash impacts of settled energy-related and interest rate derivatives are recorded as operating activities. Any cash impacts of settled foreign currency derivatives are classified as operating or financing activities to correspond with classification of the hedged interest or principal, respectively. See Note 1 to the financial statements under "Financial Instruments" in Item 8 of the Form 10-K for additional information. Energy-Related Derivatives The traditional electric operating companies, Southern Power, and Southern Company Gas enter into energy-related derivatives to hedge exposures to electricity, natural gas, and other fuel price changes. However, due to cost-based rate regulations and other various cost recovery mechanisms, the traditional electric operating companies and the natural gas distribution utilities have limited exposure to market volatility in energy-related commodity prices. Each of the traditional electric operating companies and certain of the natural gas distribution utilities of Southern Company Gas manage fuel-hedging programs, implemented per the guidelines of their respective state PSCs or other applicable state regulatory agencies, through the use of financial derivative contracts, which are expected to continue to mitigate price volatility. The traditional electric operating companies (with respect to wholesale generating capacity) and Southern Power have limited exposure to market volatility in energy-related commodity prices because their long-term sales contracts shift substantially all fuel cost responsibility to the purchaser. However, the traditional electric operating companies and Southern Power may be exposed to market volatility in energy-related commodity prices to the extent any uncontracted capacity is used to sell electricity. Southern Company Gas retains exposure to price changes that can, in a volatile energy market, be material and can adversely affect its results of operations. Southern Company Gas also enters into weather derivative contracts as economic hedges of operating margins in the event of warmer-than-normal weather. Exchange-traded options are carried at fair value, with changes reflected in operating revenues. Non-exchange-traded options are accounted for using the intrinsic value method. Changes in the intrinsic value for non-exchange-traded contracts are reflected in operating revenues. Energy-related derivative contracts are accounted for under one of three methods: • Regulatory Hedges — Energy-related derivative contracts designated as regulatory hedges relate primarily to the traditional electric operating companies' and the natural gas distribution utilities' fuel-hedging programs, where gains and losses are initially recorded as regulatory liabilities and assets, respectively, and then are included in fuel expense as the underlying fuel is used in operations and ultimately recovered through the respective fuel cost recovery clauses. • Cash Flow Hedges — Gains and losses on energy-related derivatives designated as cash flow hedges (which are mainly used to hedge anticipated purchases and sales) are initially deferred in accumulated OCI before being recognized in the statements of income in the same period and in the same income statement line item as the earnings effect of the hedged transactions. • Not Designated — Gains and losses on energy-related derivative contracts that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. Some energy-related derivative contracts require physical delivery as opposed to financial settlement, and this type of derivative is both common and prevalent within the electric and natural gas industries. When an energy-related derivative contract is settled physically, any cumulative unrealized gain or loss is reversed and the contract price is recognized in the respective line item representing the actual price of the underlying goods being delivered. Interest Rate Derivatives Southern Company and certain subsidiaries may enter into interest rate derivatives to hedge exposure to changes in interest rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. Derivatives related to existing variable rate securities or forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and presented on the same income statement line item as the earnings effect of the hedged transactions. Derivatives related to existing fixed rate securities are accounted for as fair value hedges, where the derivatives' fair value gains or losses and hedged items' fair value gains or losses are both recorded directly to earnings on the same income statement line item. Fair value gains or losses on derivatives that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. Foreign Currency Derivatives Southern Company and certain subsidiaries, including Southern Power, may enter into foreign currency derivatives to hedge exposure to changes in foreign currency exchange rates, such as that arising from the issuance of debt denominated in a currency other than U.S. dollars. Derivatives related to forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and on the same income statement line as the earnings effect of the hedged transactions, including foreign currency gains or losses arising from changes in the U.S. currency exchange rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness.

INTRODUCTION (Tables)

INTRODUCTION (Tables)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Goodwill	Goodwill at September 30, 2020 and December 31, 2019 was as follows: Goodwill (in millions) Southern Company $ 5,280 Southern Company Gas: Gas distribution operations $ 4,034 Gas marketing services 981 Southern Company Gas total $ 5,015
Schedule of Other Intangible Assets, Indefinite-Lived	Other intangible assets were as follows: At September 30, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (130) $ 82 $ 212 $ (116) $ 96 Trade names 64 (30) 34 64 (25) 39 Storage and transportation contracts 64 (64) — 64 (62) 2 PPA fair value adjustments 390 (84) 306 390 (69) 321 Other 10 (8) 2 11 (8) 3 Total other intangible assets subject to amortization $ 740 $ (316) $ 424 $ 741 $ (280) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (316) $ 499 $ 816 $ (280) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (84) $ 306 $ 390 $ (69) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (115) $ 41 $ 156 $ (104) $ 52 Trade names 26 (12) 14 26 (10) 16 Wholesale gas services Storage and transportation contracts 64 (64) — 64 (62) 2 Total other intangible assets subject to amortization $ 246 $ (191) $ 55 $ 246 $ (176) $ 70
Schedule of Other Intangible Assets, Finite-Lived	Other intangible assets were as follows: At September 30, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (130) $ 82 $ 212 $ (116) $ 96 Trade names 64 (30) 34 64 (25) 39 Storage and transportation contracts 64 (64) — 64 (62) 2 PPA fair value adjustments 390 (84) 306 390 (69) 321 Other 10 (8) 2 11 (8) 3 Total other intangible assets subject to amortization $ 740 $ (316) $ 424 $ 741 $ (280) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (316) $ 499 $ 816 $ (280) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (84) $ 306 $ 390 $ (69) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (115) $ 41 $ 156 $ (104) $ 52 Trade names 26 (12) 14 26 (10) 16 Wholesale gas services Storage and transportation contracts 64 (64) — 64 (62) 2 Total other intangible assets subject to amortization $ 246 $ (191) $ 55 $ 246 $ (176) $ 70
Finite-lived Intangible Assets Amortization Expense	Amortization associated with other intangible assets was as follows: Three Months Ended Nine Months Ended September 30, 2020 (in millions) Southern Company (a) $ 12 $ 37 Southern Power (b) $ 5 $ 15 Southern Company Gas Gas marketing services $ 4 $ 13 Wholesale gas services (b) 1 2 Southern Company Gas total $ 5 $ 15 (a) Includes $6 million and $17 million for the three and nine months ended September 30, 2020, respectively, recorded as a reduction to operating revenues. (b) Recorded as a reduction to operating revenues.
Restrictions on Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the Registrants that had restricted cash at September 30, 2020 and/or December 31, 2019: Southern Southern Power Southern At September At December 31, 2019 At September 30, 2020 At September At December 31, 2019 (in millions) (in millions) (in millions) Cash and cash equivalents $ 3,379 $ 1,975 $ 416 $ 157 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — — 3 Other current assets 4 — — 4 — Other deferred charges and assets 1 — 1 — — Total cash, cash equivalents, and restricted cash $ 3,383 (b) $ 1,978 $ 417 $ 161 $ 49 (a) For Southern Company Gas, reflects restricted cash held as collateral for workers' compensation, life insurance, and long-term disability insurance. For Southern Power, reflects restricted cash held for construction payables. (b) Total does not add due to rounding.
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the Registrants that had restricted cash at September 30, 2020 and/or December 31, 2019: Southern Southern Power Southern At September At December 31, 2019 At September 30, 2020 At September At December 31, 2019 (in millions) (in millions) (in millions) Cash and cash equivalents $ 3,379 $ 1,975 $ 416 $ 157 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — — 3 Other current assets 4 — — 4 — Other deferred charges and assets 1 — 1 — — Total cash, cash equivalents, and restricted cash $ 3,383 (b) $ 1,978 $ 417 $ 161 $ 49 (a) For Southern Company Gas, reflects restricted cash held as collateral for workers' compensation, life insurance, and long-term disability insurance. For Southern Power, reflects restricted cash held for construction payables. (b) Total does not add due to rounding.
Schedule of Changes in Asset Retirement Obligations	Details of changes in AROs for Southern Company, Alabama Power, and Georgia Power during the first nine months of 2020 are shown in the following table. There were no material changes in AROs for the other Registrants during the first nine months of 2020. Southern Company Alabama Power Georgia Power (in millions) Balance at December 31, 2019 $ 9,786 $ 3,540 $ 5,784 Liabilities incurred 15 — 10 Liabilities settled (315) (157) (130) Accretion 308 113 177 Cash flow revisions 866 462 411 Balance at September 30, 2020 $ 10,660 $ 3,958 $ 6,252

REGULATORY MATTERS (Tables)

REGULATORY MATTERS (Tables)	9 Months Ended
	Sep. 30, 2020
Regulated Operations [Abstract]
Cost Recovery Clauses	The recovery balances for certain retail regulatory clauses of the traditional electric operating companies and Southern Company Gas at September 30, 2020 and December 31, 2019 were as follows: Regulatory Clause Balance Sheet Line Item September 30, December 31, 2019 (in millions) Alabama Power Rate CNP Compliance Other regulatory liabilities, current $ 12 $ 55 Other regulatory liabilities, deferred 38 7 Rate CNP PPA Deferred under recovered regulatory clause revenues 62 40 Retail Energy Cost Recovery Other regulatory liabilities, current 107 32 Other regulatory liabilities, deferred 16 17 Natural Disaster Reserve Other regulatory liabilities, current 7 37 Other regulatory liabilities, deferred 51 113 Georgia Power Fuel Cost Recovery Over recovered fuel clause revenues $ 84 $ — Other deferred credits and liabilities 67 73 Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 23 $ 23 Ad Valorem Tax Other regulatory assets 11 47 Other regulatory assets, deferred 36 — Property Damage Reserve Other regulatory liabilities, deferred 48 54 Southern Company Gas Natural Gas Cost Recovery Other regulatory liabilities $ 84 $ 74
Cost and Schedule	Georgia Power's approximate proportionate share of the remaining estimated capital cost to complete Plant Vogtle Units 3 and 4 by the expected in-service dates of November 2021 and November 2022, respectively, is as follows: (in billions) Base project capital cost forecast (a)(b) $ 8.4 Construction contingency estimate 0.1 Total project capital cost forecast (a)(b) 8.5 Net investment as of September 30, 2020 (b) (6.9) Remaining estimate to complete (a) $ 1.6 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $240 million, of which $71 million had been accrued through September 30, 2020. (b) Net of $1.7 billion received from Toshiba under the Guarantee Settlement Agreement and approximately $188 million in related customer refunds.

REVENUE FROM CONTRACTS WITH C_2

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table disaggregates revenue from contracts with customers for the three and nine months ended September 30, 2020 and 2019: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Three Months Ended September 30, 2020 Operating revenues Retail electric revenues Residential $ 2,019 $ 752 $ 1,183 $ 84 $ — $ — Commercial 1,354 447 833 74 — — Industrial 783 358 352 73 — — Other 22 5 15 2 — — Total retail electric revenues 4,178 1,562 2,383 233 — — Natural gas distribution revenues Residential 170 — — — — 170 Commercial 41 — — — — 41 Transportation 224 — — — — 224 Industrial 4 — — — — 4 Other 35 — — — — 35 Total natural gas distribution revenues 474 — — — — 474 Wholesale electric revenues PPA energy revenues 214 40 13 2 165 — PPA capacity revenues 136 26 15 1 95 — Non-PPA revenues 59 10 3 93 68 — Total wholesale electric revenues 409 76 31 96 328 — Other natural gas revenues Wholesale gas services 431 — — — — 431 Gas marketing services 38 — — — — 38 Other natural gas revenues 7 — — — — 7 Total natural gas revenues 476 — — — — 476 Other revenues 218 33 115 6 4 — Total revenue from contracts with customers 5,755 1,671 2,529 335 332 950 Other revenue sources (a) 968 58 88 1 191 630 Other adjustments (b) (1,103) — — — — (1,103) Total operating revenues $ 5,620 $ 1,729 $ 2,617 $ 336 $ 523 $ 477 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Nine Months Ended September 30, 2020 Operating revenues Retail electric revenues Residential $ 4,802 $ 1,839 $ 2,760 $ 203 $ — $ — Commercial 3,589 1,152 2,242 195 — — Industrial 2,081 956 907 218 — — Other 68 16 46 6 — — Total retail electric revenues 10,540 3,963 5,955 622 — — Natural gas distribution revenues Residential 906 — — — — 906 Commercial 229 — — — — 229 Transportation 723 — — — — 723 Industrial 21 — — — — 21 Other 179 — — — — 179 Total natural gas distribution revenues 2,058 — — — — 2,058 Wholesale electric revenues PPA energy revenues 550 94 38 7 425 — PPA capacity revenues 339 78 30 3 231 — Non-PPA revenues 159 33 7 235 184 — Total wholesale electric revenues 1,048 205 75 245 840 — Other natural gas revenues Wholesale gas services 1,168 — — — — 1,168 Gas marketing services 258 — — — — 258 Other natural gas revenues 22 — — — — 22 Total natural gas revenues 1,448 — — — — 1,448 Other revenues 677 117 329 19 11 — Total revenue from contracts with customers 15,771 4,285 6,359 886 851 3,506 Other revenue sources (a) 2,604 160 12 9 486 1,973 Other adjustments (b) (3,117) — — — — (3,117) Total operating revenues $ 15,258 $ 4,445 $ 6,371 $ 895 $ 1,337 $ 2,362 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Three Months Ended September 30, 2019 Operating revenues Retail electric revenues Residential $ 2,119 $ 820 $ 1,211 $ 88 $ — $ — Commercial 1,563 512 965 86 — — Industrial 953 421 450 82 — — Other 26 7 16 3 — — Total retail electric revenues 4,661 1,760 2,642 259 — — Natural gas distribution revenues Residential 162 — — — — 162 Commercial 42 — — — — 42 Transportation 204 — — — — 204 Industrial 3 — — — — 3 Other 30 — — — — 30 Total natural gas distribution revenues 441 — — — — 441 Wholesale electric revenues PPA energy revenues 245 43 19 2 188 — PPA capacity revenues 134 25 13 1 100 — Non-PPA revenues 62 2 3 111 81 — Total wholesale electric revenues 441 70 35 114 369 — Other natural gas revenues Wholesale gas services 425 — — — — 425 Gas marketing services 37 — — — — 37 Other natural gas revenues 10 — — — — 10 Total natural gas revenues 472 — — — — 472 Other revenues 267 36 113 4 3 — Total revenue from contracts with customers 6,282 1,866 2,790 377 372 913 Other revenue sources (a) 855 (25) (35) (7) 202 727 Other adjustments (b) (1,142) — — — — (1,142) Total operating revenues $ 5,995 $ 1,841 $ 2,755 $ 370 $ 574 $ 498 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Nine Months Ended September 30, 2019 Operating revenues Retail electric revenues Residential $ 4,939 $ 1,971 $ 2,751 $ 217 $ — $ — Commercial 3,951 1,301 2,427 223 — — Industrial 2,428 1,128 1,074 226 — — Other 69 20 41 8 — — Total retail electric revenues 11,387 4,420 6,293 674 — — Natural gas distribution revenues Residential 992 — — — — 992 Commercial 277 — — — — 277 Transportation 673 — — — — 673 Industrial 25 — — — — 25 Other 191 — — — — 191 Total natural gas distribution revenues 2,158 — — — — 2,158 Wholesale electric revenues PPA energy revenues 648 110 47 8 508 — PPA capacity revenues 350 77 41 2 272 — Non-PPA revenues 174 65 5 275 190 — Total wholesale electric revenues 1,172 252 93 285 970 — Other natural gas revenues Wholesale gas services 1,590 — — — — 1,590 Gas marketing services 313 — — — — 313 Other natural gas revenues 32 — — — — 32 Total natural gas revenues 1,935 — — — — 1,935 Other revenues 763 119 298 14 10 — Total revenue from contracts with customers 17,415 4,791 6,684 973 980 4,093 Other revenue sources (a) 3,266 (29) 22 (3) 547 2,744 Other adjustments (b) (4,176) — — — — (4,176) Total operating revenues $ 16,505 $ 4,762 $ 6,706 $ 970 $ 1,527 $ 2,661 (a) Other revenue sources primarily relate to revenues from customers accounted for as derivatives and leases, as well as alternative revenue programs at Southern Company Gas and other cost recovery mechanisms at the traditional electric operating companies. (b) Other adjustments relate to the cost of Southern Company Gas' energy and risk management activities. Wholesale gas services revenues are presented net of the related costs of those activities on the statement of income. See Note (L) under "Southern Company Gas" for additional information on the components of wholesale gas services' operating revenues.
Contract with Customer, Asset and Liability and Revenue Recognized	The following table reflects the closing balances of receivables, contract assets, and contract liabilities related to revenues from contracts with customers at September 30, 2020 and December 31, 2019: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Accounts Receivables As of September 30, 2020 $ 2,344 $ 686 $ 901 $ 93 $ 100 $ 385 As of December 31, 2019 2,413 586 688 79 97 749 Contract Assets As of September 30, 2020 $ 159 $ 5 $ 103 $ — $ — $ — As of December 31, 2019 117 — 69 — — — Contract Liabilities As of September 30, 2020 $ 56 $ 1 $ 24 $ — $ 3 $ 1 As of December 31, 2019 52 10 13 — 1 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	Revenue from contracts with customers related to these performance obligations remaining at September 30, 2020 are expected to be recognized as follows: 2020 2021 2022 2023 2024 2025 and (in millions) Southern Company $ 170 $ 487 $ 362 $ 339 $ 319 $ 3,062 Alabama Power 7 33 31 24 7 5 Georgia Power 20 71 43 35 24 62 Southern Power 60 290 292 282 290 3,013
Summary of Lease Income	Lease income for the three and nine months ended September 30, 2020 and 2019 is as follows: Southern Alabama Power Georgia Power Mississippi Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2020 Lease income - interest income on sales-type leases $ 3 $ — $ — $ 3 $ — $ — Lease income - operating leases 50 11 14 — 21 9 Variable lease income 145 — — — 153 — Total lease income $ 198 $ 11 $ 14 $ 3 $ 174 $ 9 For the Nine Months Ended September 30, 2020 Lease income - interest income on sales-type leases $ 8 $ — $ — $ 8 $ — $ — Lease income - operating leases 148 24 44 1 66 26 Variable lease income 345 — — — 368 — Total lease income $ 501 $ 24 $ 44 $ 9 $ 434 $ 26 For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 5 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 5 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26

CONSOLIDATED ENTITIES AND EQU_2

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Regulated Operations [Abstract]
Equity Method Investments	The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2020 and December 31, 2019 and related income from those investments for the three and nine months ended September 30, 2020 and 2019 were as follows: Investment Balance September 30, 2020 December 31, 2019 (a) (in millions) SNG (b) $ 1,180 $ 1,137 PennEast Pipeline (c) 89 82 Other 32 32 Total $ 1,301 $ 1,251 (a) Excludes investments in Atlantic Coast Pipeline and Pivotal JAX LNG classified as held for sale at December 31, 2019. See Note 15 to the financial statements under "Assets Held for Sale" in Item 8 of the Form 10-K for additional information. (b) Increase primarily relates to a capital contribution, partially offset by the continued amortization of deferred tax assets established upon acquisition. (c) See Note (C) under "Other Matters – Southern Company Gas" for additional information on the PennEast Pipeline. Selected financial information of SNG for the three and nine months ended September 30, 2020 and 2019 is as follows: Income Statement Information Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) Revenues $ 150 $ 152 $ 457 $ 473 Operating income 85 82 262 274 Net income 59 60 189 208
Schedule of Other Nonoperating Income, by Component	Earnings from Equity Method Investments Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) SNG $ 30 $ 30 $ 95 $ 104 Atlantic Coast Pipeline (a)(b) — 3 3 9 PennEast Pipeline (a) 2 2 5 5 Other 1 — 3 (3) Total $ 33 $ 35 $ 106 $ 115 (a) Amounts primarily result from AFUDC equity recorded by the project entity. (b) On March 24, 2020, Southern Company Gas completed the sale of its interest in Atlantic Coast Pipeline. See Note (K) under "Southern Company Gas" for additional information.

FINANCING (Tables)

FINANCING (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Credit Arrangements by Company	At September 30, 2020, committed credit arrangements with banks were as follows: Expires Company 2021 2022 2023 2024 Total Unused Due within One Year (in millions) Southern Company parent $ — $ — $ — $ 2,000 $ 2,000 $ 1,999 $ — Alabama Power 3 525 — 800 1,328 1,328 3 Georgia Power — — — 1,750 1,750 1,728 — Mississippi Power — 150 125 — 275 250 — Southern Power (a) — — — 600 600 591 — Southern Company Gas (b) — — — 1,750 1,750 1,745 — SEGCO 30 — — — 30 30 30 Southern Company $ 33 $ 675 $ 125 $ 6,900 $ 7,733 $ 7,671 $ 33 (a) Does not include Southern Power Company's $120 million and $60 million continuing letter of credit facilities for standby letters of credit expiring in 2021 and 2023, respectively, of which $23 million and $40 million, respectively, was unused at September 30, 2020. Southern Power's subsidiaries are not parties to its bank credit arrangements or letter of credit facilities. (b) Southern Company Gas, as the parent entity, guarantees the obligations of Southern Company Gas Capital, which is the borrower of $1.25 billion of this arrangement. Southern Company Gas' committed credit arrangement also includes $500 million for which Nicor Gas is the borrower and which is restricted for working capital needs of Nicor Gas. Pursuant to this multi-year credit arrangement, the allocations between Southern Company Gas Capital and Nicor Gas may be adjusted.
Shares Used to Compute Diluted Earnings Per Share	Shares used to compute diluted earnings per share were as follows: Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) As reported shares 1,058 1,048 1,058 1,043 Effect of stock-based compensation 6 9 6 8 Diluted shares 1,064 1,057 1,064 1,051

RETIREMENT BENEFITS (Tables)

RETIREMENT BENEFITS (Tables)	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Pension Plans and Postretirement Plans	Components of the net periodic benefit costs for the three and nine months ended September 30, 2020 and 2019 are presented in the following tables. Three Months Ended September 30, 2020 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 94 $ 23 $ 24 $ 3 $ 2 $ 8 Interest cost 108 25 33 5 1 8 Expected return on plan assets (274) (66) (87) (13) (4) (20) Amortization: Prior service costs — 1 — — — (1) Regulatory asset — — — — — 4 Net (gain)/loss 67 17 22 4 1 2 Net periodic pension cost (income) $ (5) $ — $ (8) $ (1) $ — $ 1 Postretirement Benefits Service cost $ 6 $ 1 $ 2 $ (1) $ 1 $ — Interest cost 13 4 5 1 — 2 Expected return on plan assets (18) (7) (7) — — (2) Amortization: Prior service costs — — (1) — — — Regulatory asset — — — — — 2 Net (gain)/loss 1 — 1 — — (1) Net periodic postretirement benefit cost $ 2 $ (2) $ — $ — $ 1 $ 1 Nine Months Ended September 30, 2020 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 282 $ 67 $ 72 $ 11 $ 6 $ 24 Interest cost 324 75 100 15 4 23 Expected return on plan assets (824) (198) (261) (38) (10) (59) Amortization: Prior service costs 1 1 1 — — (2) Regulatory asset — — — — — 12 Net (gain)/loss 201 53 65 10 2 7 Net periodic pension cost (income) $ (16) $ (2) $ (23) $ (2) $ 2 $ 5 Postretirement Benefits Service cost $ 17 $ 4 $ 5 $ — $ 1 $ 1 Interest cost 40 10 15 2 — 5 Expected return on plan assets (54) (21) (20) (1) — (5) Amortization: Prior service costs (1) — (1) — — — Regulatory asset — — — — — 5 Net (gain)/loss 2 — 2 — — (2) Net periodic postretirement benefit cost $ 4 $ (7) $ 1 $ 1 $ 1 $ 4 Three Months Ended September 30, 2019 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 73 $ 17 $ 19 $ 3 $ 2 $ 7 Interest cost 123 28 38 6 1 9 Expected return on plan assets (222) (51) (73) (10) (2) (15) Amortization: Prior service costs 1 — — — — (1) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (5) $ — $ 1 $ 4 Postretirement Benefits Service cost $ 5 $ 1 $ 2 $ 1 $ — $ — Interest cost 18 4 6 — — 2 Expected return on plan assets (16) (6) (7) — — (1) Amortization: Prior service costs — 1 — — — — Regulatory asset — — — — — 1 Net (gain)/loss (1) — 1 — — — Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2 Nine Months Ended September 30, 2019 Southern Alabama Georgia Mississippi Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 219 $ 51 $ 56 $ 9 $ 5 $ 19 Interest cost 369 85 116 17 4 27 Expected return on plan assets (664) (154) (219) (30) (7) (45) Amortization: Prior service costs 2 1 1 — — (2) Regulatory asset — — — — — 10 Net (gain)/loss 90 27 33 4 — 2 Net periodic pension cost (income) $ 16 $ 10 $ (13) $ — $ 2 $ 11 Postretirement Benefits Service cost $ 14 $ 3 $ 4 $ 1 $ — $ 1 Interest cost 52 12 19 2 — 7 Expected return on plan assets (49) (19) (19) (1) — (4) Amortization: Prior service costs 2 3 — — — — Regulatory asset — — — — — 4 Net (gain)/loss (2) — 1 — — (2) Net periodic postretirement benefit cost $ 17 $ (1) $ 5 $ 2 $ — $ 6

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	As of September 30, 2020, 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: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Southern Company Assets: Energy-related derivatives (a) $ 488 $ 218 $ 117 $ — $ 823 Interest rate derivatives — 20 — — 20 Foreign currency derivatives — 29 — — 29 Investments in trusts: (b)(c) Domestic equity 754 137 — — 891 Foreign equity 71 220 — — 291 U.S. Treasury and government agency securities — 268 — — 268 Municipal bonds — 99 — — 99 Pooled funds – fixed income — 17 — — 17 Corporate bonds 15 376 — — 391 Mortgage and asset backed securities — 79 — — 79 Private equity — — — 68 68 Cash and cash equivalents 1 — — — 1 Other 25 6 — — 31 Cash equivalents 2,750 11 — — 2,761 Other investments 9 19 — — 28 Total $ 4,113 $ 1,499 $ 117 $ 68 $ 5,797 Liabilities: Energy-related derivatives (a) $ 521 $ 155 $ 75 $ — $ 751 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 19 — 19 Total $ 521 $ 178 $ 94 $ — $ 793 Fair Value Measurements Using: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Alabama Power Assets: Energy-related derivatives $ — $ 23 $ — $ — $ 23 Nuclear decommissioning trusts: (b) Domestic equity 477 128 — — 605 Foreign equity 71 64 — — 135 U.S. Treasury and government agency securities — 21 — — 21 Municipal bonds — 1 — — 1 Corporate bonds 15 159 — — 174 Mortgage and asset backed securities — 27 — — 27 Private equity — — — 68 68 Other 6 — — — 6 Cash equivalents 825 11 — — 836 Other investments — 19 — — 19 Total $ 1,394 $ 453 $ — $ 68 $ 1,915 Liabilities: Energy-related derivatives $ — $ 6 $ — $ — $ 6 Georgia Power Assets: Energy-related derivatives $ — $ 31 $ — $ — $ 31 Nuclear decommissioning trusts: (b)(c) Domestic equity 277 1 — — 278 Foreign equity — 153 — — 153 U.S. Treasury and government agency securities — 247 — — 247 Municipal bonds — 98 — — 98 Corporate bonds — 217 — — 217 Mortgage and asset backed securities — 52 — — 52 Other 19 6 — — 25 Cash equivalents 485 — — — 485 Total $ 781 $ 805 $ — $ — $ 1,586 Liabilities: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Fair Value Measurements Using: As of September 30, 2020: Quoted Prices Significant Significant Net Asset Value as a Practical Expedient (NAV) Total (in millions) Mississippi Power Assets: Energy-related derivatives $ — $ 18 $ — $ — $ 18 Cash equivalents 36 — — — 36 Total $ 36 $ 18 $ — $ — $ 54 Liabilities: Energy-related derivatives $ — $ 7 $ — $ — $ 7 Southern Power Assets: Energy-related derivatives $ — $ 5 $ — $ — $ 5 Foreign currency derivatives — 29 — — 29 Cash equivalents 149 — — — 149 Total $ 149 $ 34 $ — $ — $ 183 Liabilities: Energy-related derivatives $ — $ 1 $ — $ — $ 1 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 19 — 19 Total $ — $ 24 $ 19 $ — $ 43 Southern Company Gas Assets: Energy-related derivatives (a) $ 488 $ 141 $ 117 $ — $ 746 Non-qualified deferred compensation trusts: Domestic equity — 8 — — 8 Foreign equity — 3 — — 3 Pooled funds – fixed income — 17 — — 17 Cash equivalents 1 — — — 1 Cash equivalents and restricted cash 113 — — — 113 Total $ 602 $ 169 $ 117 $ — $ 888 Liabilities: Energy-related derivatives (a) $ 521 $ 132 $ 75 $ — $ 728 (a) Energy-related derivatives exclude cash collateral of $70 million. (b) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. (c) Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of September 30, 2020, approximately $25 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan to creditors under the funds' managers' securities lending program. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information.
Schedule of Increase (Decrease) In Fair Value Of Funds	The fair value of the funds, including reinvested interest and dividends and excluding the funds' expenses, increased (decreased) by the amounts shown in the table below for the three and nine months ended September 30, 2020 and 2019. The changes were recorded as a change to the regulatory assets and liabilities related to AROs for Georgia Power and Alabama Power, respectively. Fair value increases (decreases) Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 (in millions) Southern Company $ 108 $ 27 $ 85 $ 255 Alabama Power 66 15 24 140 Georgia Power 42 12 61 115
Financial Instruments for Which Carrying Amount Did Not Equal Fair Value	As of September 30, 2020, other financial instruments for which the carrying amount did not equal fair value were as follows: Southern Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (*) (in millions) Long-term debt, including securities due within one year: Carrying amount $ 49,743 $ 9,113 $ 12,700 $ 1,402 $ 4,155 $ 6,461 Fair value 56,739 10,741 15,052 1,562 4,535 7,640 (*) 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 lives of the respective bonds.
Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component	The following table includes transfers to Level 3, which represent the fair value of Southern Company Gas' commodity derivative contracts that include a significant unobservable component for the first time during the period. Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 (in millions) Beginning balance $ 80 $ 14 Transfers to Level 3 — 70 Transfers from Level 3 (2) (5) Instruments realized or otherwise settled during period (9) (16) Changes in fair value (27) (21) Ending balance $ 42 $ 42

DERIVATIVES (Tables)

DERIVATIVES (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Energy-Related Derivatives	At September 30, 2020, the net volume of energy-related derivative contracts for natural gas positions, together with the longest hedge date over which the respective entity is hedging its exposure to the variability in future cash flows for forecasted transactions and the longest non-hedge date for derivatives not designated as hedges, were as follows: Net Longest Longest (in millions) Southern Company (*) 877 2024 2031 Alabama Power 78 2024 — Georgia Power 131 2023 — Mississippi Power 86 2024 — Southern Power 14 2022 2021 Southern Company Gas (*) 568 2023 2031 (*) Southern Company Gas' derivative instruments include both long and short natural gas positions. A long position is a contract to purchase natural gas and a short position is a contract to sell natural gas. Southern Company Gas' volume represents the net of long natural gas positions of 4.6 billion mmBtu and short natural gas positions of 4.1 billion mmBtu as of September 30, 2020, which is also included in Southern Company's total volume.
Schedule of Interest Rate Derivatives	At September 30, 2020, the following interest rate derivatives were outstanding: Notional Interest Weighted Hedge Fair Value Gain (Loss) at September 30, 2020 (in millions) (in millions) Cash Flow Hedges of Existing Debt Mississippi Power $ 60 1-month LIBOR 0.58% December 2021 $ — Fair Value Hedges of Existing Debt Southern Company parent 1,500 2.35% 1-month LIBOR + 0.87% July 2021 20 Southern Company $ 1,560 $ 20
Schedule of Foreign Currency Derivatives	At September 30, 2020, the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at September 30, 2020 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ 11 Southern Power 564 3.78% 500 1.85% June 2026 (5) Total $ 1,241 € 1,100 $ 6
Fair Value of Energy-Related Derivatives and Interest Rate Derivatives	The fair value of energy-related derivatives, interest rate derivatives, and foreign currency derivatives was reflected in the balance sheets as follows: As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Southern Company Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 52 $ 13 $ 3 $ 70 Other deferred charges and assets/Other deferred credits and liabilities 30 15 6 44 Total derivatives designated as hedging instruments for regulatory purposes $ 82 $ 28 $ 9 $ 114 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 8 $ 3 $ 1 $ 6 Other deferred charges and assets/Other deferred credits and liabilities 2 — — — Interest rate derivatives: Other current assets/Other current liabilities 19 — 2 23 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 24 Other deferred charges and assets/Other deferred credits and liabilities 29 — 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 58 $ 26 $ 19 $ 54 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 392 $ 428 $ 461 $ 358 Other deferred charges and assets/Other deferred credits and liabilities 338 291 207 225 Total derivatives not designated as hedging instruments $ 730 $ 719 $ 668 $ 583 Gross amounts recognized $ 870 $ 773 $ 696 $ 751 Gross amounts offset (a) (636) (706) (463) (562) Net amounts recognized in the Balance Sheets (b) $ 234 $ 67 $ 233 $ 189 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Alabama Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 14 $ 2 $ 2 $ 14 Other deferred charges and assets/Other deferred credits and liabilities 9 4 2 10 Total derivatives designated as hedging instruments for regulatory purposes $ 23 $ 6 $ 4 $ 24 Gross amounts recognized $ 23 $ 6 $ 4 $ 24 Gross amounts offset (5) (5) (2) (2) Net amounts recognized in the Balance Sheets $ 18 $ 1 $ 2 $ 22 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 18 $ 3 $ 1 $ 32 Other deferred charges and assets/Other deferred credits and liabilities 13 6 3 21 Total derivatives designated as hedging instruments for regulatory purposes $ 31 $ 9 $ 4 $ 53 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ — $ — $ — $ 17 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ — $ — $ 17 Gross amounts recognized $ 31 $ 9 $ 4 $ 70 Gross amounts offset (9) (9) (3) (3) Net amounts recognized in the Balance Sheets $ 22 $ — $ 1 $ 67 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Mississippi Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 10 $ 2 $ — $ 15 Other deferred charges and assets/Other deferred credits and liabilities 8 5 1 12 Total derivatives designated as hedging instruments for regulatory purposes $ 18 $ 7 $ 1 $ 27 Gross amounts recognized $ 18 $ 7 $ 1 $ 27 Gross amounts offset (7) (7) (1) (1) Net amounts recognized in the Balance Sheets $ 11 $ — $ — $ 26 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 4 $ 1 $ 1 $ 2 Other deferred charges and assets/Other deferred credits and liabilities 1 — — — Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 24 Other deferred charges and assets/Other deferred credits and liabilities 29 — 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 34 $ 24 $ 17 $ 26 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ — $ — $ 2 $ 1 Total derivatives not designated as hedging instruments $ — $ — $ 2 $ 1 Gross amounts recognized $ 34 $ 24 $ 19 $ 27 Gross amounts offset (1) (1) — — Net amounts recognized in the Balance Sheets $ 33 $ 23 $ 19 $ 27 As of September 30, 2020 As of December 31, 2019 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Southern Company Gas Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 10 $ 6 $ — $ 9 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 10 $ 6 $ — $ 10 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 4 $ 2 $ — $ 4 Other deferred charges and assets/Other deferred credits and liabilities 1 — — — Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — — 2 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 5 $ 2 $ 2 $ 4 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 392 $ 428 $ 459 $ 357 Other deferred charges and assets/Other deferred credits and liabilities 338 291 207 225 Total derivatives not designated as hedging instruments $ 730 $ 719 $ 666 $ 582 Gross amounts of recognized $ 745 $ 727 $ 668 $ 596 Gross amounts offset (a) (614) (684) (456) (555) Net amounts recognized in the Balance Sheets (b) $ 131 $ 43 $ 212 $ 41 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $70 million and $99 million as of September 30, 2020 and December 31, 2019, respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $3 million and $4 million as of September 30, 2020 and December 31, 2019, respectively.
Pre-tax Effects of Unrealized Derivative Gains (Losses) Arising from Energy-Related Derivative Instruments	At September 30, 2020 and December 31, 2019, the pre-tax effects of unrealized derivative gains (losses) arising from energy-related derivative instruments designated as regulatory hedging instruments and deferred were as follows: Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet Derivative Category and Balance Sheet Southern Alabama Georgia Mississippi Southern Company Gas (in millions) At September 30, 2020: Energy-related derivatives: Other regulatory assets, current $ (5) $ — $ — $ — $ (5) Other regulatory liabilities, current 41 12 15 8 6 Other regulatory liabilities, deferred 15 5 7 3 — Total energy-related derivative gains (losses) $ 51 $ 17 $ 22 $ 11 $ 1 At December 31, 2019: Energy-related derivatives: Other regulatory assets, current $ (63) $ (14) $ (31) $ (15) $ (3) Other regulatory assets, deferred (37) (8) (18) (11) — Other regulatory liabilities, current 6 2 — — 4 Total energy-related derivative gains (losses) $ (94) $ (20) $ (49) $ (26) $ 1
Pre-tax Effects of Interest Rate Derivatives, Designated as Cash Flow Hedging Instruments	For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of cash flow hedge accounting on accumulated OCI were as follows: Gain (Loss) Recognized in OCI on Derivative For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 (in millions) (in millions) Southern Company Energy-related derivatives $ 9 $ (5) $ 2 $ (11) Interest rate derivatives 1 (52) (27) (88) Foreign currency derivatives 54 (68) (10) (107) Total $ 64 $ (125) $ (35) $ (206) Georgia Power Interest rate derivatives $ — $ (47) $ (3) $ (83) Southern Power Energy-related derivatives $ 5 $ (3) $ 2 $ (5) Foreign currency derivatives 54 (68) (10) (107) Total $ 59 $ (71) $ (8) $ (112) Southern Company Gas Energy-related derivatives $ 4 $ (2) $ — $ (6) Interest rate derivatives 1 (5) (24) (5) Total $ 5 $ (7) $ (24) $ (11)
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location	For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of cash flow and fair value hedge accounting on income were as follows: Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 (in millions) (in millions) Southern Company Total cost of natural gas $ 71 $ 79 $ 654 $ 956 Gain (loss) on energy-related cash flow hedges (a) — — (8) — Total depreciation and amortization 889 760 2,619 2,267 Gain (loss) on energy-related cash flow hedges (a) (1) (1) (3) (5) Total interest expense, net of amounts capitalized (443) (434) (1,343) (1,294) Gain (loss) on interest rate cash flow hedges (a) (6) (5) (19) (14) Gain (loss) on foreign currency cash flow hedges (a) (6) (6) (18) (18) Gain (loss) on interest rate fair value hedges (b) (3) 10 27 43 Total other income (expense), net 113 61 319 239 Gain (loss) on foreign currency cash flow hedges (a)(c) 56 (54) 52 (62) Southern Power Total depreciation and amortization $ 129 $ 120 $ 367 $ 357 Gain (loss) on energy-related cash flow hedges (a) (1) (1) (3) (5) Total interest expense, net of amounts capitalized (36) (43) (114) (127) Gain (loss) on foreign currency cash flow hedges (a) (6) (6) (18) (18) Total other income (expense), net 13 6 19 48 Gain (loss) on foreign currency cash flow hedges (a)(c) 56 (54) 52 (62) (a) Reclassified from accumulated OCI into earnings. (b) For fair value hedges, changes in the fair value of the derivative contracts are generally equal to changes in the fair value of the underlying debt and have no material impact on income. (c) The reclassification from accumulated OCI into other income (expense), net completely offsets currency gains and losses arising from changes in the U.S. currency exchange rates used to record the euro-denominated notes.
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location	As of September 30, 2020 and December 31, 2019, the following amounts were recorded on the balance sheets related to cumulative basis adjustments for fair value hedges: Carrying Amount of the Hedged Item Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item Balance Sheet Location of Hedged Items As of September 30, 2020 As of December 31, 2019 As of September 30, 2020 As of December 31, 2019 (in millions) (in millions) Southern Company Securities due within one year $ (1,513) $ (599) $ (15) $ — Long-term debt — (1,494) — 3
Pre-tax Effect of Interest Rate and Energy Related Derivatives	For the three and nine months ended September 30, 2020 and 2019, the pre-tax effects of energy-related derivatives not designated as hedging instruments on the statements of income of Southern Company and Southern Company Gas were as follows: Gain (Loss) Three Months Ended September 30, Nine Months Ended September 30, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2020 2019 2020 2019 (in millions) (in millions) Energy-related derivatives: Natural gas revenues (*) $ (30) $ (2) $ 54 $ 81 Cost of natural gas 5 2 18 5 Total derivatives in non-designated hedging relationships $ (25) $ — $ 72 $ 86 (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented.

ACQUISITIONS AND DISPOSITIONS (

ACQUISITIONS AND DISPOSITIONS (Tables)	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Schedule of Asset Acquisitions	During the nine months ended September 30, 2020, Southern Power acquired a controlling interest in the wind facility listed below. Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller Approximate Nameplate Capacity ( MW ) Location Southern Power COD PPA Contract Period Beech Ridge II Wind Invenergy Renewables LLC 56 Greenbrier County, 100% of Class A (*) May 2020 12 years (*) In May 2020, Southern Power purchased 100% of the Class A membership interests and now owns the controlling interest in the project, with the Class B member, Invenergy Renewables LLC, owning the noncontrolling interest.
Schedule of Construction Projects	Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Nine Months Ended September 30, 2020 Reading (a) Wind 200 Osage and Lyon Counties, KS May 2020 12 years Projects Under Construction as of September 30, 2020 Skookumchuck (b) Wind 136 Lewis and Thurston Counties, WA November 2020 20 years Garland Solar Storage (c) Battery energy storage system 88 Kern County, CA Second quarter 2021 20 years Tranquillity Solar Storage (c) Battery energy storage system 72 Fresno County, CA Second quarter 2021 20 years (a) In 2018, Southern Power purchased 100% of the membership interests of the Reading facility pursuant to a joint development arrangement. At the time the facility was placed in service, Southern Power recorded an operating lease right-of-use asset and an operating lease liability, each in the amount of $24 million. In June 2020, Southern Power completed a tax equity transaction whereby it received $156 million and now owns 100% of the Class B membership interests. (b) In October 2019, Southern Power purchased 100% of the membership interests of the Skookumchuck facility pursuant to a joint development arrangement. Southern Power expects to complete a tax equity transaction upon commercial operation and retain the Class B membership interests. Shortly after the completed tax equity transaction, Southern Power may sell a noncontrolling interest in these Class B membership interests to another partner. Southern Power would retain the controlling ownership interest in the facility. The ultimate outcome of these matters cannot be determined at this time. (c) Prior to commercial operation, Southern Power may enter into one or more partnerships, in which case it would ultimately own less than 100% of the Class B membership interests, but would retain ownership of the controlling interest. The ultimate outcome of this matter cannot be determined at this time.
Disposal Groups, Including Discontinued Operations	Plants Nacogdoches (sold in June 2019) and Mankato represented individually significant components of Southern Power; therefore, pre-tax income for these components for the three months ended September 30, 2019 and the nine months ended September 30, 2020 and 2019 is presented below: Three Months Ended Nine Months Ended September 30, 2020 2019 (in millions) Southern Power's earnings before income taxes: (*) Plant Nacogdoches $ — N/A $ 16 Plant Mankato $ 12 $ 2 $ 20 (*) Earnings before income taxes for components reflect the cessation of depreciation and amortization on the long-lived assets being sold upon classification as held for sale in November 2018 and April 2019 for Plant Mankato and Plant Nacogdoches, respectively.

SEGMENT AND RELATED INFORMATI_2

SEGMENT AND RELATED INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Financial Data for Business Segments	Financial data for business segments and products and services for the three and nine months ended September 30, 2020 and 2019 was as follows: Electric Utilities Traditional Southern Eliminations Total Southern Company Gas All Eliminations Consolidated (in millions) Three Months Ended September 30, 2020 Operating revenues $ 4,629 $ 523 $ (103) $ 5,049 $ 477 $ 132 $ (38) $ 5,620 Segment net income (loss) (a) 1,284 74 — 1,358 14 (122) 1 1,251 Nine Months Ended September 30, 2020 Operating revenues $ 11,576 $ 1,337 $ (285) $ 12,628 $ 2,362 $ 380 $ (112) $ 15,258 Segment net income (loss) (a)(b)(c)(d) 2,571 212 — 2,783 360 (420) 9 2,732 At September 30, 2020 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 85,218 13,424 (671) 97,971 21,932 4,116 (861) 123,158 Three Months Ended September 30, 2019 Operating revenues $ 4,908 $ 574 $ (119) $ 5,363 $ 498 $ 146 $ (12) $ 5,995 Segment net income (loss) (a)(e)(f) 1,373 86 — 1,459 (29) (110) (4) 1,316 Nine Months Ended September 30, 2019 Operating revenues $ 12,252 $ 1,527 $ (331) $ 13,448 $ 2,661 $ 514 $ (118) $ 16,505 Segment net income (loss) (a)(e)(f)(g) 2,719 316 — 3,035 347 931 (15) 4,298 At December 31, 2019 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 81,063 14,300 (713) 94,650 21,687 3,511 (1,148) 118,700 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes a pre-tax charge of $149 million ($111 million after tax) related to Plant Vogtle Units 3 and 4. See Note (B) under "Georgia Power – Nuclear Construction" for additional information. (c) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $154 million ($74 million after tax) related to a leveraged lease investment. See Note (C) under "Other Matters – Southern Company" for additional information. (d) Segment net income (loss) for Southern Power includes a $39 million pre-tax gain ($23 million gain after tax) on the sale of Plant Mankato. See Note (K) under "Southern Power" for additional information. (e) Segment net income (loss) for Southern Company Gas includes a pre-tax impairment charge of $92 million ($65 million after tax) related to a natural gas storage facility in Louisiana. See Note 3 to the financial statements under "Other Matters – Southern Company Gas – Natural Gas Storage Facilities" in Item 8 of the Form 10-K for additional information. (f) Segment net income (loss) for the "All Other" column includes the preliminary pre-tax gain associated with the sale of Gulf Power of $2.5 billion ($1.3 billion after tax) for the nine months ended September 30, 2019, as well as impairment charges in contemplation of the sales of two of PowerSecure's business units totaling $18 million and $50 million for the three and nine months ended September 30, 2019, respectively. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company" for additional information. (g) Segment net income (loss) for Southern Power includes a $23 million pre-tax gain ($88 million gain after tax) on the sale of Plant Nacogdoches. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Power – Sale of Natural Gas and Biomass Plants" for additional information. Business segment financial data for the three and nine months ended September 30, 2020 and 2019 was as follows: Gas Distribution Operations Gas Pipeline Investments Wholesale Gas Services (a) Gas Marketing Services Total All Other (b) Eliminations Consolidated (in millions) Three Months Ended September 30, 2020 Operating revenues $ 479 $ 8 $ (51) $ 39 $ 475 $ 8 $ (6) $ 477 Segment net income (loss) 46 23 (45) (3) 21 (7) — 14 Nine Months Ended September 30, 2020 Operating revenues $ 2,086 $ 24 $ (19) $ 272 $ 2,363 $ 24 $ (25) $ 2,362 Segment net income (loss) 284 74 (45) 59 372 (12) — 360 Total assets at September 30, 2020 18,715 1,609 650 1,461 22,435 10,979 (11,482) 21,932 Three Months Ended September 30, 2019 Operating revenues $ 448 $ 8 $ (2) $ 39 $ 493 $ 10 $ (5) $ 498 Segment net income (loss) 37 6 (9) (4) 30 (59) — (29) Nine Months Ended September 30, 2019 Operating revenues $ 2,188 $ 24 $ 132 $ 326 $ 2,670 $ 34 $ (43) $ 2,661 Segment net income (loss) 228 63 61 54 406 (59) — 347 Total assets at December 31, 2019 18,204 1,678 850 1,496 22,228 10,759 (11,300) 21,687 (a) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. A reconciliation of operating revenues and intercompany revenues is shown in the following table. Third Party Gross Revenues Intercompany Revenues Total Gross Revenues Less Gross Gas Costs Operating Revenues (in millions) Three Months Ended September 30, 2020 $ 1,050 $ 33 $ 1,083 $ 1,134 $ (51) Three Months Ended September 30, 2019 1,138 72 1,210 1,212 (2) Nine Months Ended September 30, 2020 $ 3,089 $ 81 $ 3,170 $ 3,189 $ (19) Nine Months Ended September 30, 2019 4,287 223 4,510 4,378 132 (b) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $92 million ($65 million after tax) for the three and nine months ended September 30, 2019 related to a natural gas storage facility in Louisiana. See Note 3 to the financial statements under "Other Matters – Southern Company Gas – Natural Gas Storage Facilities" in Item 8 of the Form 10-K for additional information.
Financial Data for Products and Services	Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended September 30, 2020 $ 4,243 $ 584 $ 222 $ 5,049 Three Months Ended September 30, 2019 4,512 625 226 5,363 Nine Months Ended September 30, 2020 $ 10,503 $ 1,473 $ 652 $ 12,628 Nine Months Ended September 30, 2019 11,136 1,667 645 13,448 Southern Company Gas' Revenues Gas Wholesale Gas Services (*) Gas Other Total (in millions) Three Months Ended September 30, 2020 $ 476 $ (51) $ 39 $ 13 $ 477 Three Months Ended September 30, 2019 445 (2) 39 16 498 Nine Months Ended September 30, 2020 $ 2,072 $ (19) $ 272 $ 37 $ 2,362 Nine Months Ended September 30, 2019 2,169 132 326 34 2,661 (*) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. See "Southern Company Gas" herein for additional information.

INTRODUCTION - Narrative (Detai

INTRODUCTION - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2020USD ($)facility	Sep. 30, 2020USD ($)	Mar. 31, 2020	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		$ 5,280		$ 5,280		$ 5,280
SOUTHERN Co GAS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		5,015		5,015		$ 5,015
Inventory decrement					$ 10
ALABAMA POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Asset retirement obligation, period increase	$ 462
Number of facilities, closure designs completed | facility	1
GEORGIA POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Asset retirement obligation, period increase		411
PowerSecure
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		$ 263		$ 263
Maximum | Natural Gas Generating Facility | SOUTHERN POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life			45 years	50 years

INTRODUCTION - Goodwill (Detail

INTRODUCTION - Goodwill (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 5,280	$ 5,280
SOUTHERN Co GAS
Goodwill [Line Items]
Goodwill	5,015	5,015
SOUTHERN Co GAS | Gas Distribution Operations
Goodwill [Line Items]
Goodwill	4,034	4,034
SOUTHERN Co GAS | Gas Marketing Services
Goodwill [Line Items]
Goodwill	$ 981	$ 981

INTRODUCTION - Other Intangible

INTRODUCTION - Other Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other intangible assets subject to amortization:
Gross Carrying Amount	$ 740	$ 741
Accumulated Amortization	(316)	(280)
Other Intangible Assets, Net	424	461
Other intangible assets not subject to amortization:
Federal Communications Commission licenses	75	75
Total other intangible assets
Gross Carrying Amount	815	816
Accumulated Amortization	(316)	(280)
Other Intangible Assets, Net	499	536
Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	212	212
Accumulated Amortization	(130)	(116)
Other Intangible Assets, Net	82	96
Total other intangible assets
Accumulated Amortization	(130)	(116)
Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(30)	(25)
Other Intangible Assets, Net	34	39
Total other intangible assets
Accumulated Amortization	(30)	(25)
Storage and transportation contracts
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(64)	(62)
Other Intangible Assets, Net	0	2
Total other intangible assets
Accumulated Amortization	(64)	(62)
PPA fair value adjustments
Other intangible assets subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(84)	(69)
Other Intangible Assets, Net	306	321
Total other intangible assets
Accumulated Amortization	(84)	(69)
Other
Other intangible assets subject to amortization:
Gross Carrying Amount	10	11
Accumulated Amortization	(8)	(8)
Other Intangible Assets, Net	2	3
Total other intangible assets
Accumulated Amortization	(8)	(8)
SOUTHERN POWER CO
Other intangible assets subject to amortization:
Accumulated Amortization	(84)	(69)
Total other intangible assets
Accumulated Amortization	(84)	(69)
SOUTHERN POWER CO | PPA fair value adjustments
Other intangible assets subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(84)	(69)
Other Intangible Assets, Net	306	321
Total other intangible assets
Accumulated Amortization	(84)	(69)
SOUTHERN Co GAS
Other intangible assets subject to amortization:
Gross Carrying Amount	246	246
Accumulated Amortization	(191)	(176)
Other Intangible Assets, Net	55	70
Total other intangible assets
Accumulated Amortization	(191)	(176)
Other Intangible Assets, Net	55	70
SOUTHERN Co GAS | Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	156	156
Accumulated Amortization	(115)	(104)
Other Intangible Assets, Net	41	52
Total other intangible assets
Accumulated Amortization	(115)	(104)
SOUTHERN Co GAS | Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	26	26
Accumulated Amortization	(12)	(10)
Other Intangible Assets, Net	14	16
Total other intangible assets
Accumulated Amortization	(12)	(10)
SOUTHERN Co GAS | Storage and transportation contracts
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(64)	(62)
Other Intangible Assets, Net	0	2
Total other intangible assets
Accumulated Amortization	$ (64)	$ (62)

INTRODUCTION - Other Intangib_2

INTRODUCTION - Other Intangible Assets, Amortization (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 12	$ 37
Decrease in operating revenues	6	17
SOUTHERN POWER CO
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5	15
SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5	15
Gas Marketing Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	4	13
Wholesale Gas Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1	$ 2

INTRODUCTION - Restricted Cash

INTRODUCTION - Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 3,379	$ 1,975
Restricted cash:
Total cash, cash equivalents, and restricted cash	3,383	1,978	$ 2,935	$ 1,519
Other accounts and notes receivable
Restricted cash:
Restricted cash	0	3
Other current assets
Restricted cash:
Restricted cash	4	0
Other deferred charges and assets
Restricted cash:
Restricted cash	1	0
SOUTHERN POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	416	279
Restricted cash:
Total cash, cash equivalents, and restricted cash	417	279	368	181
SOUTHERN POWER CO | Other accounts and notes receivable
Restricted cash:
Restricted cash	0
SOUTHERN POWER CO | Other current assets
Restricted cash:
Restricted cash	0
SOUTHERN POWER CO | Other deferred charges and assets
Restricted cash:
Restricted cash	1
SOUTHERN Co GAS
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	157	46
Restricted cash:
Total cash, cash equivalents, and restricted cash	161	49	$ 62	$ 70
SOUTHERN Co GAS | Other accounts and notes receivable
Restricted cash:
Restricted cash	0	3
SOUTHERN Co GAS | Other current assets
Restricted cash:
Restricted cash	4	0
SOUTHERN Co GAS | Other deferred charges and assets
Restricted cash:
Restricted cash	$ 0	$ 0

INTRODUCTION - Asset Retirement

INTRODUCTION - Asset Retirement Obligations (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2019	$ 9,786
Liabilities incurred	15
Liabilities settled	(315)
Accretion	308
Cash flow revisions	866
Balance at September 30, 2020	10,660
ALABAMA POWER CO
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2019	3,540
Liabilities incurred	0
Liabilities settled	(157)
Accretion	113
Cash flow revisions	462
Balance at September 30, 2020	3,958
GEORGIA POWER CO
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2019	5,784
Liabilities incurred	10
Liabilities settled	(130)
Accretion	177
Cash flow revisions	411
Balance at September 30, 2020	$ 6,252

REGULATORY MATTERS - Cost Recov

REGULATORY MATTERS - Cost Recovery Clauses (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
ALABAMA POWER CO | Other regulatory liabilities, current
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 12	$ 55
Retail Energy Cost Recovery	107	32
Natural Disaster Reserve	7	37
ALABAMA POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	38	7
Retail Energy Cost Recovery	16	17
Natural Disaster Reserve	51	113
ALABAMA POWER CO | Deferred under recovered regulatory clause revenues
Loss Contingencies [Line Items]
Rate CNP PPA	62	40
GEORGIA POWER CO | Over recovered fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	84	0
GEORGIA POWER CO | Other deferred credits and liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	67	73
MISSISSIPPI POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Property Damage Reserve	48	54
MISSISSIPPI POWER CO | Over recovered regulatory clause liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	23	23
MISSISSIPPI POWER CO | Other regulatory assets
Loss Contingencies [Line Items]
Ad Valorem Tax	11	47
MISSISSIPPI POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Ad Valorem Tax	36	0
SOUTHERN Co GAS | Other regulatory liabilities
Loss Contingencies [Line Items]
Natural Gas Cost Recovery	$ 84	$ 74

REGULATORY MATTERS - Alabama Po

REGULATORY MATTERS - Alabama Power (Details) - ALABAMA POWER CO $ in Millions	3 Months Ended
	Sep. 30, 2020USD ($)	Aug. 14, 2020USD ($)MW	Aug. 07, 2020USD ($)
Public Utilities, General Disclosures [Line Items]
Approved additional generating capacity, purchases (in MWs) | MW		240
Approved additional generating capacity, demand-side management and distributed energy resource programs (in MWs) | MW		200
Additional generating capacity (in MWs) | MW		400
Bill credits			$ 100
Decrease in NDR for damages incurred	$ 44
Natural disaster reserve	51
Minimum natural disaster reserve balance, triggering establishment charge	50
Natural disaster reserve authorized limit	$ 75
Plant Barry Unit 8
Public Utilities, General Disclosures [Line Items]
Approved additional generating capacity, construction (in MWs) | MW		720
Costs incurred, percentage of estimated in-service costs		5.00%
Estimated in-service cost		$ 652

REGULATORY MATTERS - Georgia Po

REGULATORY MATTERS - Georgia Power (Details) - GEORGIA POWER CO - USD ($)	May 28, 2020	Sep. 30, 2020	Sep. 30, 2020	Oct. 01, 2020	Dec. 31, 2019	Dec. 31, 2013
Public Utilities, General Disclosures [Line Items]
Retail rate of return on common equity						10.95%
Customer refund liability in absence of base rate case					$ 60,000,000
Portion of actual earnings above approved ROE band refunded to customers, value					$ 60,000,000
Incremental COVID-19 costs deferred		$ 38,000,000	$ 38,000,000
Requested decrease in fuel billings	$ 740,000,000	$ 44,000,000
Requested decrease in fuel billings, term	2 years
Adjustment to fuel cost recovery rate if under recovered fuel balance exceeds budget thereafter			$ 200,000,000
Subsequent Event | Traditional Base
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount, due in next fiscal year				$ 120,000,000
Subsequent Event | Environmental Compliance Cost Recovery
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount, due in next fiscal year				2,000,000
Subsequent Event | Demand-Side Management
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount, due in next fiscal year				(15,000,000)
Subsequent Event | Municipal Franchise Fee
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease), amount, due in next fiscal year				$ 4,000,000
Maximum
Public Utilities, General Disclosures [Line Items]
Retail rate of return on common equity					12.00%

REGULATORY MATTERS - Nuclear Co

REGULATORY MATTERS - Nuclear Construction (Details) $ in Millions

Jan. 01, 2021

Aug. 31, 2020USD ($)

Jan. 01, 2020

Jan. 11, 2018USD ($)

Jan. 01, 2016

Apr. 30, 2020

Dec. 31, 2019USD ($)report

Dec. 31, 2018appeal

Sep. 30, 2020USD ($)

Sep. 30, 2020USD ($)

Dec. 31, 2022USD ($)

Dec. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)report

Dec. 31, 2012utilityMW

Dec. 31, 2009USD ($)

Jun. 30, 2020USD ($)

Aug. 31, 2018

Jun. 30, 2018USD ($)

Dec. 31, 2013

Loss Contingencies [Line Items]

Construction contingency estimate

$ 5

$ 5

GEORGIA POWER CO

Loss Contingencies [Line Items]

Additional construction capital costs

$ 3,300

Estimated in-service capital cost

$ 4,418

Financing costs collected, net of tax

$ 2,500

Decrease in NCCR tariff

$ 142

Amendment to estimated in-service capital cost

$ 5,680

Retail rate of return on common equity

10.95%

Number of appeals | appeal

2

GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Proportionate ownership share

45.70%

45.70%

Number of construction units approved | utility

2

Electric generating capacity in mega watts under consortium agreement | MW

1,100

Construction costs incurred

$ 2,500

Construction contingency estimate

$ 366

Construction contingency estimate, amount in excess of original estimate

$ 34

Construction contingency estimate, additional amount

$ 115

115

Estimated loss on Plant Vogtle Units 3 and 4

149

149

Estimated loss on plants under construction, after tax

111

111

Expected percentage of positions eliminated

20.00%

Base project capital cost forecast, monthly

50

Monthly AFUDC

10

Percentage of ownership interest required for voting for continuing construction

90.00%

Production tax credits, aggregate purchase price, maximum

300

Preliminary estimated cost to complete

8,500

$ 8,500

Remaining share of construction costs, agreement to pay, percentage

100.00%

Percentage of costs, disallowed for recovery

6.00%

Costs disallowed for recovery, period

6 months

Public utilities, extension project schedule, term

1 year

Cost settlement agreement revised forecast, net of payments

7,300

$ 7,300

Public utilities, approved return on equity percentage

8.30%

10.00%

Public utilities, approved return on equity, monthly percentage decrease

0.10%

Return on equity reduction, negative impact on earnings

$ 75

GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | Scenario, Forecast

Loss Contingencies [Line Items]

Construction costs incurred

$ 3,000

Public utilities, approved return on equity percentage

5.30%

Return on equity reduction, negative impact on earnings

$ 200

$ 255

$ 145

GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | Vogtle Owners

Loss Contingencies [Line Items]

Period of notice required in the event letters of credit are not renewed

30 days

Twenty Second Construction Monitoring Report | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Number of approved construction management reports | report

22

22

Requested capital construction costs

$ 7,400

Guarantor obligations

$ 1,700

1,700

Customer refund

$ 188

Twenty Third Construction Monitoring Report | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Requested capital construction costs

$ 701

Minimum | GEORGIA POWER CO | COVID-19

Loss Contingencies [Line Items]

Estimate of possible loss

70

$ 70

Maximum | GEORGIA POWER CO

Loss Contingencies [Line Items]

Retail rate of return on common equity

12.00%

12.00%

Maximum | GEORGIA POWER CO | COVID-19

Loss Contingencies [Line Items]

Estimate of possible loss

115

115

Category I | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Preliminary estimated cost to complete

$ 8,400

8,400

Additional construction capital costs, threshold

$ 800

Category II | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

55.70%

Additional construction capital costs

$ 80

Category II | GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | Vogtle Owners

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

44.30%

Category II | Minimum | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

$ 800

Category II | Maximum | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

$ 1,600

Category III | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

65.70%

Additional construction capital costs

$ 100

Category III | GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | Vogtle Owners

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

34.30%

Category III | Maximum | GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

$ 2,100

REGULATORY MATTERS - Nuclear _2

REGULATORY MATTERS - Nuclear Construction Cost and Schedule (Details) - GEORGIA POWER CO - Plant Vogtle Units 3 And 4 $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Loss Contingencies [Line Items]
Base project capital cost forecast	$ 8,400
Construction contingency estimate	100
Total project capital cost forecast	8,500
Net investment as of September 30, 2019	(6,900)
Remaining estimate to complete	1,600
Expected capitalized costs	240
Capitalized interest accrued	$ 71

REGULATORY MATTERS - Mississipp

REGULATORY MATTERS - Mississippi Power (Details) - MISSISSIPPI POWER CO - USD ($) $ in Millions	Jun. 25, 2020	Mar. 17, 2020	Sep. 30, 2020
Loss Contingencies [Line Items]
Decrease in retail rates, percentage		1.85%
Base rate case filing, measurement input, average equity ratio		53.00%
Base rate case filing, measurement input, maximum equity ratio		55.00%
Base rate case filing, measurement input, return on investment		7.57%
Regulatory asset, amortization period		4 years
Regulatory liability, amortization period		3 years
Annual base rate adjustment, increase in depreciation		$ 10
Annual base rate adjustment, compensation costs excluded		3.9
Incremental COVID-19 costs deferred			$ 2
Increase in retail rates	$ 2	$ (16.7)

REGULATORY MATTERS - Southern C

REGULATORY MATTERS - Southern Company Gas (Details) - USD ($) $ in Millions	Jul. 01, 2020	Jun. 01, 2020	Sep. 30, 2020
Nicor Gas
Loss Contingencies [Line Items]
Requested rate increase		$ 49.6
Requested rate increase, projected test year, period		12 months
Requested return on equity percentage		10.35%
Requested equity ratio percentage		54.00%
Atlanta Gas Light
Loss Contingencies [Line Items]
Requested rate increase	$ 37.6
Requested rate increase, projected test year, period	12 months
Maximum base rate	5.00%
COVID-19 | Nicor Gas
Loss Contingencies [Line Items]
Regulatory assets			$ 13
COVID-19 | Virginia Natural Gas
Loss Contingencies [Line Items]
Regulatory assets			$ 1

CONTINGENCIES - General Litigat

CONTINGENCIES - General Litigation Matters (Details) $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)	Mar. 31, 2019plaintiff	Nov. 30, 2018USD ($)defendantplaintiff	May 31, 2018USD ($)agreement	Sep. 30, 2020USD ($)	Dec. 31, 2018	Dec. 31, 2017claim
Pending Litigation | Putative Securities Class Action
Loss Contingencies [Line Items]
Increase in the purported class period							1 day
Pending Litigation | Shareholder Derivative Lawsuits
Loss Contingencies [Line Items]
Pending number of claims | claim							2
Stay period						30 days
MISSISSIPPI POWER CO | Pending Litigation | Purported Violations Of Mississippi Consumer Protection Act
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff		4	10
Number of defendants | defendant			3
Underpayment of refunds			$ 23.5
MISSISSIPPI POWER CO | Settled Litigation | Martin Product Sales, LLC Litigation
Loss Contingencies [Line Items]
Number of agreements | agreement				2
Damages sought by litigation				$ 143	$ 76
Compensatory damages sought by litigation	$ 5
Punitive damages sought by litigation	$ 50

CONTINGENCIES - Environmental R

CONTINGENCIES - Environmental Remediation (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
GEORGIA POWER CO
Loss Contingencies [Line Items]
Environmental remediation liability, current and former sites	$ 15	$ 15
SOUTHERN Co GAS
Loss Contingencies [Line Items]
Environmental remediation liability, current and former sites	$ 252	$ 269

CONTINGENCIES - Other Matters (

CONTINGENCIES - Other Matters (Details) - USD ($) $ in Millions

Apr. 24, 2020

Apr. 23, 2020

Feb. 20, 2020

Dec. 31, 2019

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Sep. 30, 2019

Mar. 31, 2019

Sep. 30, 2020

Sep. 30, 2019

Dec. 31, 2025

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Loss Contingencies [Line Items]

Leveraged lease investments impairment loss

$ 0

$ 154

$ 0

$ 154

$ 0

Leveraged lease investments impairment loss, net of tax

$ 74

Liabilities settled

315

Liabilities incurred

15

MISSISSIPPI POWER CO

Loss Contingencies [Line Items]

Firm transportation agreement, term

15 years

MISSISSIPPI POWER CO | Kemper IGCC

Loss Contingencies [Line Items]

Liabilities settled

2

Government grants received

$ 387

MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC

Loss Contingencies [Line Items]

Liabilities incurred

$ 3

GULF POWER CO | Plant Daniel Units 1 And 2

Loss Contingencies [Line Items]

Undivided ownership interest to be restructured

50.00%

Undivided ownership interest, ownership interest in individual unit

100.00%

100.00%

Minimum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC

Loss Contingencies [Line Items]

Liabilities incurred

$ 10

$ 10

$ 10

$ 10

$ 10

Maximum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC

Loss Contingencies [Line Items]

Liabilities incurred

$ 15

$ 15

$ 15

$ 15

$ 15

PennEast Pipelines

Loss Contingencies [Line Items]

Construction contingency, extension request, term

2 years

PennEast Pipelines | SOUTHERN Co GAS

Loss Contingencies [Line Items]

Construction contingency estimate

$ 300

$ 300

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Disaggregate Revenue Sources (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenues	$ 5,755	$ 6,282	$ 15,771	$ 17,415
Revenues	5,620	5,995	15,258	16,505
Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	4,178	4,661	10,540	11,387
Residential
Disaggregation of Revenue [Line Items]
Operating revenues	2,019	2,119	4,802	4,939
Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	1,354	1,563	3,589	3,951
Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	783	953	2,081	2,428
Other
Disaggregation of Revenue [Line Items]
Operating revenues	22	26	68	69
Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	474	441	2,058	2,158
Residential
Disaggregation of Revenue [Line Items]
Operating revenues	170	162	906	992
Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	41	42	229	277
Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	224	204	723	673
Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	4	3	21	25
Other
Disaggregation of Revenue [Line Items]
Operating revenues	35	30	179	191
Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	409	441	1,048	1,172
PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	214	245	550	648
PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	136	134	339	350
Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	59	62	159	174
Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	476	472	1,448	1,935
Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	431	425	1,168	1,590
Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	38	37	258	313
Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	7	10	22	32
Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	218	267	677	763
Other revenue sources
Disaggregation of Revenue [Line Items]
Other	968	855	2,604	3,266
Other adjustments
Disaggregation of Revenue [Line Items]
Other	(1,103)	(1,142)	(3,117)	(4,176)
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	1,671	1,866	4,285	4,791
Revenues	1,729	1,841	4,445	4,762
ALABAMA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	1,562	1,760	3,963	4,420
ALABAMA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	752	820	1,839	1,971
ALABAMA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	447	512	1,152	1,301
ALABAMA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	358	421	956	1,128
ALABAMA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	5	7	16	20
ALABAMA POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	76	70	205	252
ALABAMA POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	40	43	94	110
ALABAMA POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	26	25	78	77
ALABAMA POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	10	2	33	65
ALABAMA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
ALABAMA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	33	36	117	119
ALABAMA POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Other	58	(25)	160	(29)
ALABAMA POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Other	0	0	0	0
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	2,529	2,790	6,359	6,684
Revenues	2,617	2,755	6,371	6,706
GEORGIA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	2,383	2,642	5,955	6,293
GEORGIA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	1,183	1,211	2,760	2,751
GEORGIA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	833	965	2,242	2,427
GEORGIA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	352	450	907	1,074
GEORGIA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	15	16	46	41
GEORGIA POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	31	35	75	93
GEORGIA POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	13	19	38	47
GEORGIA POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	15	13	30	41
GEORGIA POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	3	3	7	5
GEORGIA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
GEORGIA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	115	113	329	298
GEORGIA POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Other	88	(35)	12	22
GEORGIA POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Other	0	0	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	335	377	886	973
Revenues	336	370	895	970
MISSISSIPPI POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	233	259	622	674
MISSISSIPPI POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	84	88	203	217
MISSISSIPPI POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	74	86	195	223
MISSISSIPPI POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	73	82	218	226
MISSISSIPPI POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	2	3	6	8
MISSISSIPPI POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	96	114	245	285
MISSISSIPPI POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	2	2	7	8
MISSISSIPPI POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	1	1	3	2
MISSISSIPPI POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	93	111	235	275
MISSISSIPPI POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
MISSISSIPPI POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	6	4	19	14
MISSISSIPPI POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Other	1	(7)	9	(3)
MISSISSIPPI POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Other	0	0	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	332	372	851	980
Revenues	523	574	1,337	1,527
SOUTHERN POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	328	369	840	970
SOUTHERN POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	165	188	425	508
SOUTHERN POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	95	100	231	272
SOUTHERN POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	68	81	184	190
SOUTHERN POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	4	3	11	10
SOUTHERN POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Other	191	202	486	547
SOUTHERN POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Other	0	0	0	0
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Operating revenues	950	913	3,506	4,093
Revenues	477	498	2,362	2,661
SOUTHERN Co GAS | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	474	441	2,058	2,158
SOUTHERN Co GAS | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	170	162	906	992
SOUTHERN Co GAS | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	41	42	229	277
SOUTHERN Co GAS | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	224	204	723	673
SOUTHERN Co GAS | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	4	3	21	25
SOUTHERN Co GAS | Other
Disaggregation of Revenue [Line Items]
Operating revenues	35	30	179	191
SOUTHERN Co GAS | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	476	472	1,448	1,935
SOUTHERN Co GAS | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	431	425	1,168	1,590
SOUTHERN Co GAS | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	38	37	258	313
SOUTHERN Co GAS | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	7	10	22	32
SOUTHERN Co GAS | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0	0
SOUTHERN Co GAS | Other revenue sources
Disaggregation of Revenue [Line Items]
Other	630	727	1,973	2,744
SOUTHERN Co GAS | Other adjustments
Disaggregation of Revenue [Line Items]
Other	$ (1,103)	$ (1,142)	$ (3,117)	$ (4,176)

REVENUE FROM CONTRACTS WITH C_4

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Contract Balances (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Accounts Receivables	$ 2,344	$ 2,413
Contract Assets	159	117
Contract Liabilities	56	52
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivables	686	586
Contract Assets	5	0
Contract Liabilities	1	10
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivables	901	688
Contract Assets	103	69
Contract Liabilities	24	13
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivables	93	79
Contract Assets	0	0
Contract Liabilities	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivables	100	97
Contract Assets	0	0
Contract Liabilities	3	1
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivables	385	749
Contract Assets	0	0
Contract Liabilities	$ 1	$ 1

REVENUE FROM CONTRACTS WITH C_5

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Narrative (Details) - USD ($) $ in Millions	Aug. 31, 2020	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Contract assets		$ 159	$ 159	$ 117
Contract liabilities		56	56	52
Revenue from contracts with customers recognized		8	29
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract assets		47	47	40
Contract liabilities		22	$ 22	28
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing			Georgia Power had contract assets primarily related to fixed retail customer bill programs, where the payment is contingent upon Georgia Power's continued performance and the customer's continued participation in the program over a one-year contract term, and unregulated service agreements, where payment is contingent on project completion. Contract liabilities for Georgia Power relate to cash collections recognized in advance of revenue for certain unregulated service agreements. Alabama Power had contract liabilities for outstanding performance obligations primarily related to extended service agreements.
Contract assets		103	$ 103	69
Contract liabilities		24	24	13
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract assets		5	5	0
Contract liabilities		1	1	10
ALABAMA POWER CO | Autauga Combined Cycle
Disaggregation of Revenue [Line Items]
Power sales agreement, remaining term	3 years
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract assets		0	0	0
Contract liabilities		0	0	$ 0
Sales-type lease, lease receivable		25	25
Transfer of construction work in progress to lease receivables		25
MISSISSIPPI POWER CO | Other Property and Investments
Disaggregation of Revenue [Line Items]
Sales-type lease, lease receivable		22	22
MISSISSIPPI POWER CO | Other Accounts Notes and Loans Receivable
Disaggregation of Revenue [Line Items]
Sales-type lease, lease receivable		$ 3	$ 3

REVENUE FROM CONTRACTS WITH C_6

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Performance Obligations (Details) $ in Millions	Sep. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 170
Performance obligation, expected timing of satisfaction	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 487
Performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 362
Performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 339
Performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 319
Performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 3,062
Performance obligation, expected timing of satisfaction
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 7
Performance obligation, expected timing of satisfaction	3 months
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 33
Performance obligation, expected timing of satisfaction	1 year
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 31
Performance obligation, expected timing of satisfaction	1 year
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 24
Performance obligation, expected timing of satisfaction	1 year
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 7
Performance obligation, expected timing of satisfaction	1 year
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 5
Performance obligation, expected timing of satisfaction
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 20
Performance obligation, expected timing of satisfaction	3 months
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 71
Performance obligation, expected timing of satisfaction	1 year
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 43
Performance obligation, expected timing of satisfaction	1 year
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 35
Performance obligation, expected timing of satisfaction	1 year
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 24
Performance obligation, expected timing of satisfaction	1 year
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 62
Performance obligation, expected timing of satisfaction
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 60
Performance obligation, expected timing of satisfaction	3 months
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 290
Performance obligation, expected timing of satisfaction	1 year
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 292
Performance obligation, expected timing of satisfaction	1 year
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 282
Performance obligation, expected timing of satisfaction	1 year
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 290
Performance obligation, expected timing of satisfaction	1 year
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 3,013
Performance obligation, expected timing of satisfaction

REVENUE FROM CONTRACTS WITH C_7

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Summary of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 3	$ 2	$ 8	$ 7
Lease income - operating leases	50	64	148	216
Variable lease income	145	141	345	324
Total lease income	198	207	501	547
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	11	5	24	19
Variable lease income	0	0	0	0
Total lease income	11	5	24	19
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	14	18	44	57
Variable lease income	0	0	0	0
Total lease income	14	18	44	57
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	3	2	8	7
Lease income - operating leases	0	0	1	0
Variable lease income	0	0	0	0
Total lease income	3	2	9	7
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	21	31	66	111
Variable lease income	153	151	368	349
Total lease income	174	182	434	460
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	9	9	26	26
Variable lease income	0	0	0	0
Total lease income	$ 9	$ 9	$ 26	$ 26

CONSOLIDATED ENTITIES AND EQU_3

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)investor	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Assets	$ 123,158	$ 118,700
Liabilities	90,367	86,650
Equity method investments	403	391
SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets	13,424	14,300
Liabilities	6,813	7,678
Equity method investments	$ 19	28
SP Solar Holdings I, LP | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	67.00%
SP Solar Holdings I, LP | Global Atlantic
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	33.00%
Variable Interest Entity, Primary Beneficiary | SP Solar Holdings I, LP | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets	$ 6,300	6,400
Liabilities	382	382
Noncontrolling interests related to other partners' interests	1,100	1,100
Variable Interest Entity, Primary Beneficiary | SP Wind | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets	2,400	2,500
Liabilities	129	128
Noncontrolling interests related to other partners' interests	$ 44	45
Distribution made to limited partner, cash distributions paid, percentage	60.00%
Number of financial investors | investor	3
Variable Interest Entity, Primary Beneficiary | SP Wind | Financial Investors
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	40.00%
Variable Interest Entity, Primary Beneficiary | Other Variable Interest Entities | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets	$ 1,100
Liabilities	109	104
Noncontrolling interests related to other partners' interests	$ 471	$ 409

CONSOLIDATED ENTITIES AND EQU_4

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Balance Sheet Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,358	$ 1,303
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,301	1,251
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,180	1,137
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Investment Balance	89	82
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 32	$ 32

CONSOLIDATED ENTITIES AND EQU_5

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Income Statement Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 33	$ 39	$ 105	$ 120
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	33	35	106	115
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	30	30	95	104
SOUTHERN Co GAS | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	0	3	3	9
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	2	2	5	5
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 1	$ 0	$ 3	$ (3)

CONSOLIDATED ENTITIES AND EQU_6

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Investment in SNG (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Operating income	1,835	2,013	4,156	7,046
Net income	1,283	1,345	2,746	4,335
Equity Method Investment | SNG
Schedule of Equity Method Investments [Line Items]
Revenues	150	152	457	473
Operating income	85	82	262	274
Net income	$ 59	$ 60	$ 189	$ 208

FINANCING - Schedule of Credit

FINANCING - Schedule of Credit Arrangements (Details)	Sep. 30, 2020USD ($)
Line of Credit Facility [Line Items]
Expires, 2021	$ 33,000,000
Expires, 2022	675,000,000
Expires, 2023	125,000,000
Expires, 2024	6,900,000,000
Total	7,733,000,000
Unused	7,671,000,000
Due within One Year	33,000,000
Southern Company
Line of Credit Facility [Line Items]
Expires, 2021	0
Expires, 2022	0
Expires, 2023	0
Expires, 2024	2,000,000,000
Total	2,000,000,000
Unused	1,999,000,000
Due within One Year	0
ALABAMA POWER CO
Line of Credit Facility [Line Items]
Expires, 2021	3,000,000
Expires, 2022	525,000,000
Expires, 2023	0
Expires, 2024	800,000,000
Total	1,328,000,000
Unused	1,328,000,000
Due within One Year	3,000,000
GEORGIA POWER CO
Line of Credit Facility [Line Items]
Expires, 2021	0
Expires, 2022	0
Expires, 2023	0
Expires, 2024	1,750,000,000
Total	1,750,000,000
Unused	1,728,000,000
Due within One Year	0
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
Expires, 2021	0
Expires, 2022	150,000,000
Expires, 2023	125,000,000
Expires, 2024	0
Total	275,000,000
Unused	250,000,000
Due within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
Expires, 2021	0
Expires, 2022	0
Expires, 2023	0
Expires, 2024	600,000,000
Total	600,000,000
Unused	591,000,000
Due within One Year	0
SOUTHERN POWER CO | Standby Letters of Credit
Line of Credit Facility [Line Items]
Expires, 2021	120,000,000
Expires, 2024	60,000,000
Unused, 2021	23,000,000
Unused, 2023	40,000,000
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
Expires, 2021	0
Expires, 2022	0
Expires, 2023	0
Expires, 2024	1,750,000,000
Total	1,750,000,000
Unused	1,745,000,000
Due within One Year	0
SEGCO
Line of Credit Facility [Line Items]
Expires, 2021	30,000,000
Expires, 2022	0
Expires, 2023	0
Expires, 2024	0
Total	30,000,000
Unused	30,000,000
Due within One Year	30,000,000
Southern Company Gas Capital
Line of Credit Facility [Line Items]
Total	1,250,000,000
Nicor Gas
Line of Credit Facility [Line Items]
Total	$ 500,000,000

FINANCING - Narrative (Details)

FINANCING - Narrative (Details) $ in Millions	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
Line of credit expiring in 2023	$ 125
Variable rate pollution control revenue bonds outstanding	1,400
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Line of credit expiring in 2023	125
Variable rate pollution control revenue bonds outstanding	34
ALABAMA POWER CO
Debt Instrument [Line Items]
Line of credit expiring in 2023	0
Variable rate pollution control revenue bonds outstanding	854
GEORGIA POWER CO
Debt Instrument [Line Items]
Line of credit expiring in 2023	0
Variable rate pollution control revenue bonds outstanding	550
Fixed rate pollution control revenue bonds outstanding	$ 257

FINANCING - Shares Used to Comp

FINANCING - Shares Used to Compute Diluted Earnings Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Disclosure [Abstract]
As reported shares (in shares)	1,058,000,000	1,048,000,000	1,058,000,000	1,043,000,000
Effect of stock-based compensation (in shares)	6,000,000	9,000,000	6,000,000	8,000,000
Diluted shares (in shares)	1,064,000,000	1,057,000,000	1,064,000,000	1,051,000,000
Antidilutive securities excluded from computation of earnings per share (in shares)	0			0

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Billions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	13.90%	30.20%
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	12.30%	22.60%
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	12.70%	16.30%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	11.30%	(13.60%)
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	21.40%	15.00%
ITC and PTC carryforwards
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	$ 1.5		$ 1.8

RETIREMENT BENEFITS (Details)

RETIREMENT BENEFITS (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Amortization:
Net (gain)/loss
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year	$ 0		$ 0
Pension Plans and Postretirement Plans
Service cost	94,000,000	73,000,000	282,000,000	$ 219,000,000
Interest cost	108,000,000	123,000,000	324,000,000	369,000,000
Expected return on plan assets	(274,000,000)	(222,000,000)	(824,000,000)	(664,000,000)
Amortization:
Prior service costs	0	1,000,000	1,000,000	2,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	67,000,000	30,000,000	201,000,000	90,000,000
Net periodic pension cost (income)	(5,000,000)	5,000,000	(16,000,000)	16,000,000
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	23,000,000	17,000,000	67,000,000	51,000,000
Interest cost	25,000,000	28,000,000	75,000,000	85,000,000
Expected return on plan assets	(66,000,000)	(51,000,000)	(198,000,000)	(154,000,000)
Amortization:
Prior service costs	1,000,000	0	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	17,000,000	9,000,000	53,000,000	27,000,000
Net periodic pension cost (income)	0	3,000,000	(2,000,000)	10,000,000
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	24,000,000	19,000,000	72,000,000	56,000,000
Interest cost	33,000,000	38,000,000	100,000,000	116,000,000
Expected return on plan assets	(87,000,000)	(73,000,000)	(261,000,000)	(219,000,000)
Amortization:
Prior service costs	0	0	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	22,000,000	11,000,000	65,000,000	33,000,000
Net periodic pension cost (income)	(8,000,000)	(5,000,000)	(23,000,000)	(13,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	3,000,000	11,000,000	9,000,000
Interest cost	5,000,000	6,000,000	15,000,000	17,000,000
Expected return on plan assets	(13,000,000)	(10,000,000)	(38,000,000)	(30,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	4,000,000	1,000,000	10,000,000	4,000,000
Net periodic pension cost (income)	(1,000,000)	0	(2,000,000)	0
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	6,000,000	5,000,000
Interest cost	1,000,000	1,000,000	4,000,000	4,000,000
Expected return on plan assets	(4,000,000)	(2,000,000)	(10,000,000)	(7,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	1,000,000	0	2,000,000	0
Net periodic pension cost (income)	0	1,000,000	2,000,000	2,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	8,000,000	7,000,000	24,000,000	19,000,000
Interest cost	8,000,000	9,000,000	23,000,000	27,000,000
Expected return on plan assets	(20,000,000)	(15,000,000)	(59,000,000)	(45,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)	(2,000,000)	(2,000,000)
Regulatory asset	4,000,000	3,000,000	12,000,000	10,000,000
Net (gain)/loss	2,000,000	1,000,000	7,000,000	2,000,000
Net periodic pension cost (income)	1,000,000	4,000,000	5,000,000	11,000,000
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	6,000,000	5,000,000	17,000,000	14,000,000
Interest cost	13,000,000	18,000,000	40,000,000	52,000,000
Expected return on plan assets	(18,000,000)	(16,000,000)	(54,000,000)	(49,000,000)
Amortization:
Prior service costs	0	0	(1,000,000)	2,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	1,000,000	(1,000,000)	2,000,000	(2,000,000)
Net periodic pension cost (income)	2,000,000	6,000,000	4,000,000	17,000,000
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	4,000,000	3,000,000
Interest cost	4,000,000	4,000,000	10,000,000	12,000,000
Expected return on plan assets	(7,000,000)	(6,000,000)	(21,000,000)	(19,000,000)
Amortization:
Prior service costs	0	1,000,000	0	3,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	(2,000,000)	0	(7,000,000)	(1,000,000)
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	5,000,000	4,000,000
Interest cost	5,000,000	6,000,000	15,000,000	19,000,000
Expected return on plan assets	(7,000,000)	(7,000,000)	(20,000,000)	(19,000,000)
Amortization:
Prior service costs	(1,000,000)	0	(1,000,000)	0
Regulatory asset	0	0	0	0
Net (gain)/loss	1,000,000	1,000,000	2,000,000	1,000,000
Net periodic pension cost (income)	0	2,000,000	1,000,000	5,000,000
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	(1,000,000)	1,000,000	0	1,000,000
Interest cost	1,000,000	0	2,000,000	2,000,000
Expected return on plan assets	0	0	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	0	1,000,000	1,000,000	2,000,000
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	0	1,000,000	0
Interest cost	0	0	0	0
Expected return on plan assets	0	0	0	0
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	1,000,000	0	1,000,000	0
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	0	1,000,000	1,000,000
Interest cost	2,000,000	2,000,000	5,000,000	7,000,000
Expected return on plan assets	(2,000,000)	(1,000,000)	(5,000,000)	(4,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	2,000,000	1,000,000	5,000,000	4,000,000
Net (gain)/loss	(1,000,000)	0	(2,000,000)	(2,000,000)
Net periodic pension cost (income)	$ 1,000,000	$ 2,000,000	$ 4,000,000	$ 6,000,000

FAIR VALUE MEASUREMENTS - Asset

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Derivatives	$ 234	$ 233
Liabilities:
Derivatives	67	189
Collateral already posted, assets, aggregate fair value	70
ALABAMA POWER CO
Assets:
Derivatives	18	2
Liabilities:
Derivatives	1	22
GEORGIA POWER CO
Assets:
Derivatives	22	1
Investments in trusts	25
Liabilities:
Derivatives	0	67
MISSISSIPPI POWER CO
Assets:
Derivatives	11	0
Liabilities:
Derivatives	0	26
SOUTHERN POWER CO
Assets:
Derivatives	33	19
Liabilities:
Derivatives	23	27
SOUTHERN Co GAS
Assets:
Derivatives	131	212
Liabilities:
Derivatives	43	41
Collateral already posted, assets, aggregate fair value	70	$ 99
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	2,761
Other investments	28
Total	5,797
Liabilities:
Contingent consideration	19
Total	793
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	2,750
Other investments	9
Total	4,113
Liabilities:
Contingent consideration	0
Total	521
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	11
Other investments	19
Total	1,499
Liabilities:
Contingent consideration	0
Total	178
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Other investments	0
Total	117
Liabilities:
Contingent consideration	19
Total	94
Fair Value, Measurements, Recurring | Net Asset Value as a Practical Expedient (NAV)
Assets:
Total	68
Fair Value, Measurements, Recurring | Energy-related derivatives
Assets:
Derivatives	823
Liabilities:
Derivatives	751
Fair Value, Measurements, Recurring | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	488
Liabilities:
Derivatives	521
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	218
Liabilities:
Derivatives	155
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	117
Liabilities:
Derivatives	75
Fair Value, Measurements, Recurring | Interest rate derivatives
Assets:
Derivatives	20
Fair Value, Measurements, Recurring | Interest rate derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Fair Value, Measurements, Recurring | Interest rate derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	20
Fair Value, Measurements, Recurring | Interest rate derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Fair Value, Measurements, Recurring | Foreign currency derivatives
Assets:
Derivatives	29
Liabilities:
Derivatives	23
Fair Value, Measurements, Recurring | Foreign currency derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Foreign currency derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	29
Liabilities:
Derivatives	23
Fair Value, Measurements, Recurring | Foreign currency derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Domestic equity
Assets:
Investments in trusts	891
Fair Value, Measurements, Recurring | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	754
Fair Value, Measurements, Recurring | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	137
Fair Value, Measurements, Recurring | Domestic equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Foreign equity
Assets:
Investments in trusts	291
Fair Value, Measurements, Recurring | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	71
Fair Value, Measurements, Recurring | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	220
Fair Value, Measurements, Recurring | Foreign equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities
Assets:
Investments in trusts	268
Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	268
Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Municipal bonds
Assets:
Investments in trusts	99
Fair Value, Measurements, Recurring | Municipal bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Municipal bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	99
Fair Value, Measurements, Recurring | Municipal bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Pooled funds – fixed income
Assets:
Investments in trusts	17
Fair Value, Measurements, Recurring | Pooled funds – fixed income | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Pooled funds – fixed income | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	17
Fair Value, Measurements, Recurring | Pooled funds – fixed income | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Corporate bonds
Assets:
Investments in trusts	391
Fair Value, Measurements, Recurring | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	15
Fair Value, Measurements, Recurring | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	376
Fair Value, Measurements, Recurring | Corporate bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Mortgage and asset backed securities
Assets:
Investments in trusts	79
Fair Value, Measurements, Recurring | Mortgage and asset backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Mortgage and asset backed securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	79
Fair Value, Measurements, Recurring | Mortgage and asset backed securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Private equity
Assets:
Investments in trusts	68
Fair Value, Measurements, Recurring | Private equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Private equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Private equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Private equity | Net Asset Value as a Practical Expedient (NAV)
Assets:
Investments in trusts	68
Fair Value, Measurements, Recurring | Cash and cash equivalents
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Other
Assets:
Investments in trusts	31
Fair Value, Measurements, Recurring | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	25
Fair Value, Measurements, Recurring | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | Other | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO
Assets:
Cash equivalents	836
Other investments	19
Total	1,915
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	825
Other investments	0
Total	1,394
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	11
Other investments	19
Total	453
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Other investments	0
Total	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Net Asset Value as a Practical Expedient (NAV)
Assets:
Total	68
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives
Assets:
Derivatives	23
Liabilities:
Derivatives	6
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	23
Liabilities:
Derivatives	6
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity
Assets:
Investments in trusts	605
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	477
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	128
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity
Assets:
Investments in trusts	135
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	71
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	64
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | U.S. Treasury and government agency securities
Assets:
Investments in trusts	21
Fair Value, Measurements, Recurring | ALABAMA POWER CO | U.S. Treasury and government agency securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | U.S. Treasury and government agency securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	21
Fair Value, Measurements, Recurring | ALABAMA POWER CO | U.S. Treasury and government agency securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Municipal bonds
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Municipal bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Municipal bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Municipal bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds
Assets:
Investments in trusts	174
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	15
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	159
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Mortgage and asset backed securities
Assets:
Investments in trusts	27
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Mortgage and asset backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Mortgage and asset backed securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	27
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Mortgage and asset backed securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Private equity
Assets:
Investments in trusts	68
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Private equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Private equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Private equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Private equity | Net Asset Value as a Practical Expedient (NAV)
Assets:
Investments in trusts	68
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO
Assets:
Cash equivalents	485
Total	1,586
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	485
Total	781
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	805
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Energy-related derivatives
Assets:
Derivatives	31
Liabilities:
Derivatives	9
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	31
Liabilities:
Derivatives	9
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity
Assets:
Investments in trusts	278
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	277
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Foreign equity
Assets:
Investments in trusts	153
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	153
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Foreign equity | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | U.S. Treasury and government agency securities
Assets:
Investments in trusts	247
Fair Value, Measurements, Recurring | GEORGIA POWER CO | U.S. Treasury and government agency securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | U.S. Treasury and government agency securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	247
Fair Value, Measurements, Recurring | GEORGIA POWER CO | U.S. Treasury and government agency securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Municipal bonds
Assets:
Investments in trusts	98
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Municipal bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Municipal bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	98
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Municipal bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Corporate bonds
Assets:
Investments in trusts	217
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	217
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Corporate bonds | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Mortgage and asset backed securities
Assets:
Investments in trusts	52
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Mortgage and asset backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Mortgage and asset backed securities | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	52
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Mortgage and asset backed securities | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other
Assets:
Investments in trusts	25
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	19
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO
Assets:
Cash equivalents	36
Total	54
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	36
Total	36
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	18
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	0
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Energy-related derivatives
Assets:
Derivatives	18
Liabilities:
Derivatives	7
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	18
Liabilities:
Derivatives	7
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO
Assets:
Cash equivalents	149
Total	183
Liabilities:
Contingent consideration	19
Total	43
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	149
Total	149
Liabilities:
Contingent consideration	0
Total	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	34
Liabilities:
Contingent consideration	0
Total	24
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	0
Liabilities:
Contingent consideration	19
Total	19
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives
Assets:
Derivatives	5
Liabilities:
Derivatives	1
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	5
Liabilities:
Derivatives	1
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives
Assets:
Derivatives	29
Liabilities:
Derivatives	23
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	29
Liabilities:
Derivatives	23
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS
Assets:
Cash equivalents	113
Total	888
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	113
Total	602
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	169
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	117
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives
Assets:
Derivatives	746
Liabilities:
Derivatives	728
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	488
Liabilities:
Derivatives	521
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	141
Liabilities:
Derivatives	132
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	117
Liabilities:
Derivatives	75
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Domestic equity
Assets:
Non-qualified deferred compensation trusts	8
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	8
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Domestic equity | Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Foreign equity
Assets:
Non-qualified deferred compensation trusts	3
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	3
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Foreign equity | Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Pooled funds – fixed income
Assets:
Non-qualified deferred compensation trusts	17
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Pooled funds – fixed income | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Pooled funds – fixed income | Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	17
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Pooled funds – fixed income | Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash equivalents
Assets:
Non-qualified deferred compensation trusts	1
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	1
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash equivalents | Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash equivalents | Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	$ 0

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Increase (Decrease) In Fair Value Of Funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 108	$ 27	$ 85	$ 255
ALABAMA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	66	15	24	140
GEORGIA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 42	$ 12	$ 61	$ 115

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Sep. 30, 2020USD ($)$ / MMBTU
ALABAMA POWER CO | Private equity
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	$ 68
Unfunded commitments	67
SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3) | Energy-related derivatives
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value of derivatives	$ 42
SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3) | Energy-related derivatives | Forward Price | Valuation, Market Approach | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Measurement input (usd per mmbtu) | $ / MMBTU	(1.11)
SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3) | Energy-related derivatives | Forward Price | Valuation, Market Approach | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Measurement input (usd per mmbtu) | $ / MMBTU	0.24

FAIR VALUE MEASUREMENTS - Finan

FAIR VALUE MEASUREMENTS - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions	Sep. 30, 2020USD ($)
Long-term debt, including securities due within one year:
Carrying amount	$ 49,743
Fair value	56,739
ALABAMA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	9,113
Fair value	10,741
GEORGIA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	12,700
Fair value	15,052
MISSISSIPPI POWER CO
Long-term debt, including securities due within one year:
Carrying amount	1,402
Fair value	1,562
SOUTHERN POWER CO
Long-term debt, including securities due within one year:
Carrying amount	4,155
Fair value	4,535
SOUTHERN Co GAS
Long-term debt, including securities due within one year:
Carrying amount	6,461
Fair value	$ 7,640

FAIR VALUE MEASUREMENTS - Fair

FAIR VALUE MEASUREMENTS - Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component (Details) - SOUTHERN Co GAS - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 80	$ 14
Transfers to Level 3	0	70
Transfers from Level 3	(2)	(5)
Instruments realized or otherwise settled during period	(9)	(16)
Changes in fair value	(27)	(21)
Ending balance	$ 42	$ 42

DERIVATIVES - Energy-Related De

DERIVATIVES - Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Sep. 30, 2020MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	877
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	78
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	131
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	86
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	14
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	568
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Long
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume	4,600
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Short
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume	4,100

DERIVATIVES - Narrative (Detail

DERIVATIVES - Narrative (Details) MWh in Millions, MMBTU in Millions	9 Months Ended
	Sep. 30, 2020USD ($)MMBTUMWh	Dec. 31, 2019USD ($)
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	12
Cash flow hedge gain (loss) to be reclassified within twelve months | $	$ (25,000,000)
Collateral already posted, assets, aggregate fair value | $	$ 70,000,000
SOUTHERN POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	4
ALABAMA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	3
GEORGIA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	4
MISSISSIPPI POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	1
Parent Company and Southern Power
Derivative [Line Items]
Foreign currency cash flow hedge gain (loss) to be reclassified during next 12 months | $	$ (14,000,000)
Registrants | Derivative Counterparties
Derivative [Line Items]
Collateral already posted, assets, aggregate fair value | $	0
SOUTHERN Co GAS
Derivative [Line Items]
Collateral already posted, assets, aggregate fair value | $	$ 70,000,000	$ 99,000,000
Public Utilities, Inventory, Power Position | SOUTHERN POWER CO
Derivative [Line Items]
Net Purchased mmBtu | MWh	1

DERIVATIVES - Interest Rate Der

DERIVATIVES - Interest Rate Derivatives (Details) - Interest rate derivatives $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Derivative [Line Items]
Notional Amount	$ 1,560
Fair Value Gain (Loss) at September 30, 2020	20
MISSISSIPPI POWER CO | Cash Flow Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 60
Weighted Average Interest Rate Paid	0.58%
Fair Value Gain (Loss) at September 30, 2020	$ 0
Southern Company | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 1,500
Interest Rate Received	2.35%
Fair Value Gain (Loss) at September 30, 2020	$ 20
London Interbank Offered Rate (LIBOR) | Southern Company | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Weighted Average Interest Rate Paid	0.87%

DERIVATIVES - Foreign Currency

DERIVATIVES - Foreign Currency Derivatives (Details) - 9 months ended Sep. 30, 2020 - Cash Flow Hedges of Forecasted Debt - Foreign currency derivatives € in Millions, $ in Millions	USD ($)	EUR (€)
Derivative [Line Items]
Pay Notional	$ 1,241
Receive Notional | €		€ 1,100
Fair Value Gain (Loss) at September 30, 2020	6
SOUTHERN POWER CO | June 2022
Derivative [Line Items]
Pay Notional	$ 677
Pay Rate	2.95%
Receive Notional | €		600
Receive Rate	1.00%
Fair Value Gain (Loss) at September 30, 2020	$ 11
SOUTHERN POWER CO | June 2026
Derivative [Line Items]
Pay Notional	$ 564
Pay Rate	3.78%
Receive Notional | €		€ 500
Receive Rate	1.85%
Fair Value Gain (Loss) at September 30, 2020	$ (5)

DERIVATIVES - Derivative Financ

DERIVATIVES - Derivative Financial Statement Presentation and Amounts With Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivatives, assets	$ 870	$ 696
Derivatives, liabilities	773	751
Derivative asset, Gross amounts offset	(636)	(463)
Derivative liability, Gross amounts offset	(706)	(562)
Derivative asset	234	233
Derivative liability	67	189
Collateral already posted, assets, aggregate fair value	70
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	730	668
Derivatives, liabilities	719	583
Derivatives not designated as hedging instruments | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	392	461
Derivatives not designated as hedging instruments | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	428	358
Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	338	207
Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	291	225
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	82	9
Derivatives, liabilities	28	114
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	52	3
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	13	70
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	30	6
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	15	44
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	58	19
Derivatives, liabilities	26	54
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	8	1
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	3	6
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	19	2
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	23
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	1
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	23	24
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	29	16
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
ALABAMA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	23	4
Derivatives, liabilities	6	24
Derivative asset, Gross amounts offset	(5)	(2)
Derivative liability, Gross amounts offset	(5)	(2)
Derivative asset	18	2
Derivative liability	1	22
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	23	4
Derivatives, liabilities	6	24
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	14	2
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	14
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	9	2
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	10
GEORGIA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	31	4
Derivatives, liabilities	9	70
Derivative asset, Gross amounts offset	(9)	(3)
Derivative liability, Gross amounts offset	(9)	(3)
Derivative asset	22	1
Derivative liability	0	67
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	31	4
Derivatives, liabilities	9	53
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	18	1
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	3	32
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	13	3
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	6	21
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
Derivatives, liabilities	0	17
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	17
MISSISSIPPI POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	18	1
Derivatives, liabilities	7	27
Derivative asset, Gross amounts offset	(7)	(1)
Derivative liability, Gross amounts offset	(7)	(1)
Derivative asset	11	0
Derivative liability	0	26
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	18	1
Derivatives, liabilities	7	27
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	10	0
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	15
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	8	1
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	5	12
SOUTHERN POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	34	19
Derivatives, liabilities	24	27
Derivative asset, Gross amounts offset	(1)	0
Derivative liability, Gross amounts offset	(1)	0
Derivative asset	33	19
Derivative liability	23	27
SOUTHERN POWER CO | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	2
Derivatives, liabilities	0	1
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	2
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	34	17
Derivatives, liabilities	24	26
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	4	1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	2
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Over recovered fuel clause revenues
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	23	24
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	29	16
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN Co GAS
Derivatives, Fair Value [Line Items]
Derivatives, assets	745	668
Derivatives, liabilities	727	596
Derivative asset, Gross amounts offset	(614)	(456)
Derivative liability, Gross amounts offset	(684)	(555)
Derivative asset	131	212
Derivative liability	43	41
Collateral already posted, assets, aggregate fair value	70	99
Weather derivative premium	3	4
SOUTHERN Co GAS | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	730	666
Derivatives, liabilities	719	582
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	338	207
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	291	225
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	392	459
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	428	357
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	10	0
Derivatives, liabilities	6	10
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	1
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	10	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	6	9
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	2
Derivatives, liabilities	2	4
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	4	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	4
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	2
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	$ 0	$ 0

DERIVATIVES - Pre-tax Effects o

DERIVATIVES - Pre-tax Effects of Derivatives Designated as Cash Flow Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, assets, aggregate fair value	$ 70		$ 70
Gain (Loss) Recognized in OCI on Derivative	64	$ (125)	(35)	$ (206)
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, assets, aggregate fair value	70		70		$ 99
Gain (Loss) Recognized in OCI on Derivative	5	(7)	(24)	(11)
SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	59	(71)	(8)	(112)
Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	51		51		(94)
Gain (Loss) Recognized in OCI on Derivative	9	(5)	2	(11)
Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(5)		(5)		(63)
Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					(37)
Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	41		41		6
Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	15		15
Energy-related derivatives | ALABAMA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	17		17		(20)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		(14)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					(8)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	12		12		2
Energy-related derivatives | ALABAMA POWER CO | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	5		5
Energy-related derivatives | GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	22		22		(49)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		(31)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					(18)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	15		15		0
Energy-related derivatives | GEORGIA POWER CO | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	7		7
Energy-related derivatives | MISSISSIPPI POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	11		11		(26)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		(15)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					(11)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	8		8		0
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	3		3
Energy-related derivatives | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	1		1		1
Gain (Loss) Recognized in OCI on Derivative	4	(2)	0	(6)
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(5)		(5)		(3)
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					0
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	6		6		$ 4
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0
Energy-related derivatives | SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	5	(3)	2	(5)
Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	1	(52)	(27)	(88)
Interest rate derivatives | GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	0	(47)	(3)	(83)
Interest rate derivatives | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	1	(5)	(24)	(5)
Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	54	(68)	(10)	(107)
Foreign currency derivatives | SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	$ 54	$ (68)	$ (10)	$ (107)

DERIVATIVES - Location and Amou

DERIVATIVES - Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Total cost of sales	$ 71	$ 79	$ 654	$ 956
Depreciation and amortization	889	760	2,619	2,267
Total interest expense, net of amounts capitalized	(443)	(434)	(1,343)	(1,294)
Total other income (expense), net	113	61	319	239
Cash Flow Hedging | Energy-related derivatives | Total cost of natural gas
Derivative [Line Items]
Gain (loss) on hedge	0	0	(8)	0
Cash Flow Hedging | Energy-related derivatives | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	(1)	(3)	(5)
Cash Flow Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(5)	(19)	(14)
Cash Flow Hedging | Foreign currency derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(6)	(18)	(18)
Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	56	(54)	52	(62)
Fair Value Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(3)	10	27	43
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	129	120	367	357
Total interest expense, net of amounts capitalized	(36)	(43)	(114)	(127)
Total other income (expense), net	13	6	19	48
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	(1)	(3)	(5)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(6)	(18)	(18)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	$ 56	$ (54)	$ 52	$ (62)

DERIVATIVES - Cumulative Basis

DERIVATIVES - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Fair Value Hedging - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Securities due within one year
Derivative [Line Items]
Carrying Amount of the Hedged Item	$ (1,513)	$ (599)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	(15)	0
Long-term debt
Derivative [Line Items]
Carrying Amount of the Hedged Item	0	(1,494)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	$ 0	$ 3

DERIVATIVES - Pre-tax Effects_2

DERIVATIVES - Pre-tax Effects of Derivatives Not Designated as Hedging (Details) - Derivatives not designated as hedging instruments - Energy-related derivatives - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ (25)	$ 0	$ 72	$ 86
Natural gas revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(30)	(2)	54	81
Cost of natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 5	$ 2	$ 18	$ 5

ACQUISITIONS AND DISPOSITIONS -

ACQUISITIONS AND DISPOSITIONS - Alabama Power Narrative (Details) - ALABAMA POWER CO - Autauga Combined Cycle $ in Millions	Aug. 31, 2020USD ($)
Business Acquisition [Line Items]
Purchase price	$ 461
Property, plant, and equipment	$ 452
Power sales agreement, remaining term	3 years

ACQUISITIONS AND DISPOSITIONS_2

ACQUISITIONS AND DISPOSITIONS - Schedule of Acquisition (Details) - SOUTHERN POWER CO - MW	1 Months Ended
	May 31, 2020	Jun. 30, 2020
Business Acquisition [Line Items]
Approximate nameplate capacity (in MWs)		300
Beech Ridge II
Business Acquisition [Line Items]
Approximate nameplate capacity (in MWs)	56
PPA Contract Period	12 years
Beech Ridge II | Beech Ridge II
Business Acquisition [Line Items]
Ownership percentage by parent	100.00%

ACQUISITIONS AND DISPOSITIONS_3

ACQUISITIONS AND DISPOSITIONS - Southern Power Narrative (Details) $ in Millions	Jan. 17, 2020USD ($)	Sep. 30, 2020USD ($)agreement	Sep. 30, 2019USD ($)	Jun. 30, 2020MW	Dec. 31, 2019USD ($)	May 31, 2019MW
Business Acquisition [Line Items]
Construction work in progress		$ 8,861			$ 7,880
Preliminary gain on sale		$ 36	$ 2,517
SOUTHERN POWER CO
Business Acquisition [Line Items]
Approximate nameplate capacity (in MWs) | MW				300
Business acquisition, number of Power Purchase Agreements | agreement		2
Construction work in progress		$ 335			$ 515
Preliminary gain on sale		39	$ 24
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Mankato expansion
Business Acquisition [Line Items]
Approximate nameplate capacity (in MWs) | MW						385
Nacogdoches biomass-fueled facility	$ 663
Preliminary gain on sale	39
Preliminary gain on sale, net of tax	$ 23
SOUTHERN POWER CO | Series of Construction Projects
Business Acquisition [Line Items]
Construction work in progress		244
SOUTHERN POWER CO | Series of Construction Projects | Minimum
Business Acquisition [Line Items]
Estimated future construction payments		475
SOUTHERN POWER CO | Series of Construction Projects | Maximum
Business Acquisition [Line Items]
Estimated future construction payments		$ 545

ACQUISITIONS AND DISPOSITIONS_4

ACQUISITIONS AND DISPOSITIONS - Schedule of Construction Projects (Details) $ in Millions	1 Months Ended			3 Months Ended
	Nov. 30, 2020MW	Jun. 30, 2020USD ($)MW	May 31, 2020MW	Jun. 30, 2021MW	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 31, 2019	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Operating lease ROU assets, net | $					$ 1,791	$ 1,800
SOUTHERN POWER CO
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW) | MW		300
Operating lease ROU assets, net | $					$ 395	$ 369
SOUTHERN POWER CO | Reading
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW) | MW			200
PPA Contract Period			12 years
SOUTHERN POWER CO | Reading | Reading
Business Acquisition [Line Items]
Ownership percentage by parent								100.00%
Operating lease ROU assets, net | $								$ 24
Operating lease obligations | $								$ 24
Proceeds from tax equity transaction | $		$ 156
SOUTHERN POWER CO | Reading | Reading | Class B Membership Interest
Business Acquisition [Line Items]
Ownership percentage by parent					100.00%
SOUTHERN POWER CO | Skookumchuck | Skookumchuck
Business Acquisition [Line Items]
Ownership percentage by parent							100.00%
SOUTHERN POWER CO | Scenario, Forecast | Skookumchuck
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW) | MW	136
PPA Contract Period	20 years
SOUTHERN POWER CO | Scenario, Forecast | Garland Solar Storage
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW) | MW				88
PPA Contract Period				20 years
SOUTHERN POWER CO | Scenario, Forecast | Tranquillity Solar Storage
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW) | MW				72
PPA Contract Period				20 years

ACQUISITIONS AND DISPOSITIONS_5

ACQUISITIONS AND DISPOSITIONS - Pre-tax Profit (Details) - SOUTHERN POWER CO - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Plant Nacogdoches
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	$ 0		$ 16
Plant Mankato
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	$ 12	$ 2	$ 20

ACQUISITIONS AND DISPOSITIONS_6

ACQUISITIONS AND DISPOSITIONS - Southern Company Gas Narrative (Details) - SOUTHERN Co GAS - USD ($) $ in Millions	Mar. 24, 2020	Sep. 30, 2021	Feb. 28, 2021
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Pivotal Home Solutions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses, net of cash divested	$ 178
Pivotal LNG | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent milestone payment, amount		$ 5	$ 5

SEGMENT AND RELATED INFORMATI_3

SEGMENT AND RELATED INFORMATION - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)state	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)segmentstate	Sep. 30, 2019USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	3		3
Operating revenues	$ 5,755	$ 6,282	$ 15,771	$ 17,415
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	332	372	851	980
SOUTHERN POWER CO | Traditional Electric Operating Companies | Wholesale revenues, affiliates
Segment Reporting Information [Line Items]
Operating revenues	$ 101	116	$ 279	320
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	4		4
Operating revenues	$ 950	913	$ 3,506	4,093
Number of reportable segments | segment			4
SOUTHERN Co GAS | Traditional Electric Operating Companies | Natural gas
Segment Reporting Information [Line Items]
Operating revenues		9		13
SOUTHERN Co GAS | SOUTHERN POWER CO | Natural gas
Segment Reporting Information [Line Items]
Operating revenues	$ 9	$ 20	$ 22	$ 53
Southern Natural Gas Company, LLC | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%		50.00%
PennEast Pipelines | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	20.00%		20.00%
Dalton Pipeline | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%		50.00%
Atlantic Coast Pipeline | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	5.00%		5.00%

SEGMENT AND RELATED INFORMATI_4

SEGMENT AND RELATED INFORMATION - Financial Data for Business Segments (Details) - USD ($) $ in Millions	Jan. 17, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues		$ 5,620		$ 5,995	$ 15,258	$ 16,505
Segment net income (loss)		1,251		1,316	2,732	4,298
Goodwill		5,280			5,280		$ 5,280
Total assets		123,158			123,158		118,700
Leveraged lease investments impairment loss		0	$ 154	0	154	0
Leveraged lease investments impairment loss, net of tax			$ 74
Impairment charges		0		110	0	142
Preliminary gain on sale					36	2,517
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues		523		574	1,337	1,527
Segment net income (loss)		74		86	212	316
Total assets		13,424			13,424		14,300
Preliminary gain on sale					39	24
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Plant Mankato
Segment Reporting Information [Line Items]
Gain on sale					39
Gain on sale, net of tax					23
Preliminary gain on sale	$ 39
Preliminary gain on sale, net of tax	$ 23
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Plant Nacogdoches
Segment Reporting Information [Line Items]
Preliminary gain on sale				23
Preliminary gain on sale, net of tax				88
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		477		498	2,362	2,661
Segment net income (loss)		14		(29)	360	347
Goodwill		5,015			5,015		5,015
Total assets		21,932			21,932		21,687
Impairment charges		0		92	0	92
Impairment charges, net of tax				65		65
GEORGIA POWER CO
Segment Reporting Information [Line Items]
Operating revenues		2,617		2,755	6,371	6,706
Total assets		47,046			47,046		44,541
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues		5,049		5,363	12,628	13,448
Segment net income (loss)		1,358		1,459	2,783	3,035
Goodwill		2			2		2
Total assets		97,971			97,971		94,650
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		477		498	2,362	2,661
All Other
Segment Reporting Information [Line Items]
Leveraged lease investments impairment loss					154
Leveraged lease investments impairment loss, net of tax					74
All Other | Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Segment Reporting Information [Line Items]
Impairment charges				18		50
Preliminary pre-tax gain on sale						2,500
Preliminary after-tax gain on sale						1,300
Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill		4,034			4,034		4,034
Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		(51)		(2)	(19)	132
Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill		981			981		981
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		475		493	2,363	2,670
Segment net income (loss)		21		30	372	406
Total assets		22,435			22,435		22,228
Operating Segments | Traditional Electric Operating Companies | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues		4,629		4,908	11,576	12,252
Segment net income (loss)		1,284		1,373	2,571	2,719
Goodwill		0			0		0
Total assets		85,218			85,218		81,063
Operating Segments | SOUTHERN POWER CO | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues		523		574	1,337	1,527
Segment net income (loss)		74		86	212	316
Goodwill		2			2		2
Total assets		13,424			13,424		14,300
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		477		498	2,362	2,661
Segment net income (loss)		14		(29)	360	347
Goodwill		5,015			5,015		5,015
Total assets		21,932			21,932		21,687
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues		132		146	380	514
Segment net income (loss)		(122)		(110)	(420)	931
Goodwill		263			263		263
Total assets		4,116			4,116		3,511
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		8		10	24	34
Segment net income (loss)		(7)		(59)	(12)	(59)
Total assets		10,979			10,979		10,759
Operating Segments | Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		479		448	2,086	2,188
Segment net income (loss)		46		37	284	228
Total assets		18,715			18,715		18,204
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		8		8	24	24
Segment net income (loss)		23		6	74	63
Total assets		1,609			1,609		1,678
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		(51)		(2)	(19)	132
Segment net income (loss)		(45)		(9)	(45)	61
Total assets		650			650		850
Operating Segments | Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		39		39	272	326
Segment net income (loss)		(3)		(4)	59	54
Total assets		1,461			1,461		1,496
Eliminations
Segment Reporting Information [Line Items]
Operating revenues		(38)		(12)	(112)	(118)
Segment net income (loss)		1		(4)	9	(15)
Goodwill		0			0		0
Total assets		(861)			(861)		(1,148)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		(6)		(5)	(25)	(43)
Segment net income (loss)		0		0	0	0
Total assets		(11,482)			(11,482)		(11,300)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues		(103)		(119)	(285)	(331)
Segment net income (loss)		0		$ 0	0	$ 0
Goodwill		0			0		0
Total assets		(671)			(671)		$ (713)
Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Segment Reporting Information [Line Items]
Estimated loss on Plant Vogtle Units 3 and 4		149			149
Estimated loss on plants under construction, after tax		$ 111			$ 111

SEGMENT AND RELATED INFORMATI_5

SEGMENT AND RELATED INFORMATION - Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Concentration Risk [Line Items]
Operating revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Less Gross Gas Costs	71	79	654	956
Impairment charges	0	110	0	142
Retail
Concentration Risk [Line Items]
Operating revenues	4,243	4,512	10,503	11,136
Wholesale
Concentration Risk [Line Items]
Operating revenues	584	625	1,473	1,667
Other
Concentration Risk [Line Items]
Operating revenues	164	163	484	492
Electric Utilities' Revenues
Concentration Risk [Line Items]
Operating revenues	5,049	5,363	12,628	13,448
Electric Utilities' Revenues | Retail
Concentration Risk [Line Items]
Operating revenues	4,243	4,512	10,503	11,136
Electric Utilities' Revenues | Wholesale
Concentration Risk [Line Items]
Operating revenues	584	625	1,473	1,667
Electric Utilities' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	222	226	652	645
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	477	498	2,362	2,661
Southern Company Gas' Revenues | Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	476	445	2,072	2,169
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	(51)	(2)	(19)	132
Southern Company Gas' Revenues | Gas Marketing Services
Concentration Risk [Line Items]
Operating revenues	39	39	272	326
Southern Company Gas' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	13	16	37	34
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	477	498	2,362	2,661
Impairment charges	0	92	0	92
Impairment charges, net of tax		65		65
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	(51)	(2)	(19)	132
Less Gross Gas Costs	1,134	1,212	3,189	4,378
Third Party Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	1,050	1,138	3,089	4,287
Intercompany Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	33	72	81	223
Total Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	$ 1,083	$ 1,210	$ 3,170	$ 4,510