Southern Power 10-Q 30 Apr 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page	3 Months Ended
	Mar. 31, 2020shares
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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)	1,055,955,711
Entity Central Index Key	0000092122
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
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
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
	Mar. 31, 2020	Mar. 31, 2019
Operating Revenues:
Total operating revenues	$ 5,018	$ 5,412
Operating Expenses:
Total cost of natural gas	439	686
Other operations and maintenance	1,296	1,314
Depreciation and amortization	857	751
Taxes other than income taxes	330	329
(Gain) loss on dispositions, net	(39)	(2,497)
Total operating expenses	3,755	1,721
Operating Income	1,263	3,691
Other Income and (Expense):
Allowance for equity funds used during construction	34	32
Earnings from equity method investments	42	48
Interest expense, net of amounts capitalized	(456)	(430)
Other income (expense), net	103	78
Total other income and (expense)	(277)	(272)
Earnings Before Income Taxes	986	3,419
Income taxes	145	1,360
Consolidated Net Income	841	2,059
Dividends on preferred stock of subsidiaries	4	4
Net loss attributable to noncontrolling interests	(31)	(29)
Net Income (Loss)	$ 868	$ 2,084
Earnings per share -
Basic (in dollars per share)	$ 0.82	$ 2.01
Diluted (in dollars per share)	$ 0.81	$ 1.99
Average number of shares of common stock outstanding (in millions)
Basic (in shares)	1,057	1,038
Diluted (in shares)	1,067	1,045
Retail electric revenues
Operating Revenues:
Total operating revenues	$ 3,078	$ 3,084
Wholesale electric revenues
Operating Revenues:
Total operating revenues	418	499
Other electric revenues
Operating Revenues:
Total operating revenues	151	168
Natural gas
Operating Revenues:
Total operating revenues	1,249	1,474
Operating Expenses:
Total cost of natural gas	439	686
Other
Operating Revenues:
Total operating revenues	122	187
Operating Expenses:
Total cost of natural gas	55	118
Fuel
Operating Expenses:
Total cost of natural gas	636	850
Purchased power
Operating Expenses:
Total cost of natural gas	181	170
Alternative revenue programs
Operating Revenues:
Total operating revenues	9	(2)
ALABAMA POWER CO
Operating Revenues:
Total operating revenues	1,351	1,408
Operating Expenses:
Other operations and maintenance	350	409
Depreciation and amortization	200	199
Taxes other than income taxes	106	103
Total operating expenses	929	1,070
Operating Income	422	338
Other Income and (Expense):
Allowance for equity funds used during construction	10	14
Interest expense, net of amounts capitalized	(88)	(83)
Other income (expense), net	24	14
Total other income and (expense)	(54)	(55)
Earnings Before Income Taxes	368	283
Income taxes	84	62
Consolidated Net Income	284	221
Dividends on preferred stock of subsidiaries	4	4
Net Income (Loss)	280	217
ALABAMA POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	1,205	1,213
ALABAMA POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	56	61
ALABAMA POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	19	60
ALABAMA POWER CO | Other
Operating Revenues:
Total operating revenues	71	74
ALABAMA POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	215	301
ALABAMA POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	40	37
ALABAMA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of natural gas	18	21
GEORGIA POWER CO
Operating Revenues:
Total operating revenues	1,825	1,833
Operating Expenses:
Other operations and maintenance	465	446
Depreciation and amortization	352	240
Taxes other than income taxes	113	106
Total operating expenses	1,419	1,385
Operating Income	406	448
Other Income and (Expense):
Interest expense, net of amounts capitalized	(111)	(96)
Other income (expense), net	52	40
Total other income and (expense)	(59)	(56)
Earnings Before Income Taxes	347	392
Income taxes	16	81
Consolidated Net Income	331	311
Net Income (Loss)	331	311
GEORGIA POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	1,675	1,668
GEORGIA POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	26	32
GEORGIA POWER CO | Other
Operating Revenues:
Total operating revenues	124	133
GEORGIA POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	231	299
GEORGIA POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	129	118
GEORGIA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of natural gas	129	176
MISSISSIPPI POWER CO
Operating Revenues:
Total operating revenues	277	287
Operating Expenses:
Other operations and maintenance	76	61
Depreciation and amortization	42	48
Taxes other than income taxes	29	26
Total operating expenses	231	231
Operating Income	46	56
Other Income and (Expense):
Interest expense, net of amounts capitalized	(16)	(17)
Other income (expense), net	8	5
Total other income and (expense)	(8)	(12)
Earnings Before Income Taxes	38	44
Income taxes	6	7
Consolidated Net Income	32	37
Net Income (Loss)	32	37
MISSISSIPPI POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	199	203
MISSISSIPPI POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	51	57
MISSISSIPPI POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	21	22
MISSISSIPPI POWER CO | Other
Operating Revenues:
Total operating revenues	6	5
MISSISSIPPI POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	79	93
MISSISSIPPI POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	5	3
SOUTHERN POWER CO
Operating Revenues:
Total operating revenues	375	443
Operating Expenses:
Other operations and maintenance	79	83
Depreciation and amortization	117	119
Taxes other than income taxes	9	11
(Gain) loss on dispositions, net	(39)	1
Total operating expenses	287	383
Operating Income	88	60
Other Income and (Expense):
Interest expense, net of amounts capitalized	(39)	(44)
Other income (expense), net	2	2
Total other income and (expense)	(37)	(42)
Earnings Before Income Taxes	51	18
Income taxes	7	(9)
Consolidated Net Income	44	27
Net loss attributable to noncontrolling interests	(31)	(29)
Net Income (Loss)	75	56
SOUTHERN POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	286	352
SOUTHERN POWER CO | Other
Operating Revenues:
Total operating revenues	3	4
SOUTHERN POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	107	145
SOUTHERN POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	14	24
SOUTHERN Co GAS
Operating Revenues:
Total operating revenues	1,249	1,474
Operating Expenses:
Other operations and maintenance	258	235
Depreciation and amortization	120	118
Taxes other than income taxes	72	82
Total operating expenses	889	1,121
Operating Income	360	353
Other Income and (Expense):
Earnings from equity method investments	43	48
Interest expense, net of amounts capitalized	(58)	(59)
Other income (expense), net	9	5
Total other income and (expense)	(6)	(6)
Earnings Before Income Taxes	354	347
Income taxes	79	77
Consolidated Net Income	275	270
Net Income (Loss)	275	270
SOUTHERN Co GAS | Natural gas
Operating Revenues:
Total operating revenues	1,240	1,476
Operating Expenses:
Total cost of natural gas	439	686
SOUTHERN Co GAS | Alternative revenue programs
Operating Revenues:
Total operating revenues	$ 9	$ (2)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenues	$ 5,018	$ 5,412
Alternative revenue programs
Operating revenues	9	(2)
SOUTHERN Co GAS
Operating revenues	1,249	1,474
Excise taxes collected	47	55
SOUTHERN Co GAS | Alternative revenue programs
Operating revenues	$ 9	$ (2)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 841	$ 2,059
Qualifying hedges:
Changes in fair value, net of tax	(86)	(28)
Reclassification adjustment for amounts included in net income, net of tax	38	28
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	1	0
Total other comprehensive income (loss)	(47)	0
Comprehensive Income	794	2,059
Dividends on preferred stock of subsidiaries	4	4
Comprehensive loss attributable to noncontrolling interests	(31)	(29)
Comprehensive Income (Loss) Attributable to Parent	821	2,084
ALABAMA POWER CO
Net income	284	221
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax	1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	1	1
Comprehensive Income	285	222
Dividends on preferred stock of subsidiaries	4	4
GEORGIA POWER CO
Net income	331	311
Qualifying hedges:
Changes in fair value, net of tax	(2)	0
Reclassification adjustment for amounts included in net income, net of tax	1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	(1)	1
Comprehensive Income	330	312
MISSISSIPPI POWER CO
Net income	32	37
Qualifying hedges:
Changes in fair value, net of tax	0	0
Reclassification adjustment for amounts included in net income, net of tax	0	0
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	0	0
Comprehensive Income	32	37
SOUTHERN POWER CO
Net income	44	27
Qualifying hedges:
Changes in fair value, net of tax	(62)	(29)
Reclassification adjustment for amounts included in net income, net of tax	28	25
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	1	0
Total other comprehensive income (loss)	(33)	(4)
Comprehensive Income	11	23
Comprehensive loss attributable to noncontrolling interests	(31)	(29)
Comprehensive Income (Loss) Attributable to Parent	42	52
SOUTHERN Co GAS
Net income	275	270
Qualifying hedges:
Changes in fair value, net of tax	(20)	0
Reclassification adjustment for amounts included in net income, net of tax	5	0
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0	(1)
Total other comprehensive income (loss)	(15)	(1)
Comprehensive Income	$ 260	$ 269

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Qualifying hedges:
Changes in fair value, tax	$ (30)	$ (9)
Reclassification adjustment for amounts included in net income, tax	13	9
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	2	0
ALABAMA POWER CO
Qualifying hedges:
Reclassification adjustment for amounts included in net income, tax	0	0
GEORGIA POWER CO
Qualifying hedges:
Changes in fair value, tax	(1)	0
Reclassification adjustment for amounts included in net income, tax	1	0
MISSISSIPPI POWER CO
Qualifying hedges:
Changes in fair value, tax	0	0
Reclassification adjustment for amounts included in net income, tax	0	0
SOUTHERN POWER CO
Qualifying hedges:
Changes in fair value, tax	(21)	(10)
Reclassification adjustment for amounts included in net income, tax	10	8
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), tax	0	0
Reclassification adjustment for amounts included in net income, tax	0	0
SOUTHERN Co GAS
Qualifying hedges:
Changes in fair value, tax	(7)	0
Reclassification adjustment for amounts included in net income, tax	2	0
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	$ 1	$ 0

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net income	$ 841	$ 2,059
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	949	851
Deferred income taxes	(58)	191
Allowance for equity funds used during construction	(34)	(32)
Pension, postretirement, and other employee benefits	(67)	(53)
Settlement of asset retirement obligations	(86)	(62)
Stock based compensation expense	72	64
(Gain) loss on dispositions, net	(38)	(2,503)
Other, net	111	71
Changes in certain current assets and liabilities —
-Receivables	317	378
-Prepayments	(110)	(129)
-Natural gas for sale	246	363
-Other current assets	(67)	17
-Accounts payable	(504)	(783)
-Accrued taxes	(102)	928
-Accrued compensation	(473)	(489)
-Other current liabilities	(103)	(127)
Net cash provided from operating activities	894	744
Investing Activities:
Property additions	(1,560)	(1,678)
Nuclear decommissioning trust fund purchases	(254)	(197)
Nuclear decommissioning trust fund sales	249	192
Proceeds from dispositions and asset sales	982	4,427
Cost of removal, net of salvage	(69)	(89)
Change in construction payables, net	(141)	(146)
Investment in unconsolidated subsidiaries	(77)	(10)
Payments pursuant to LTSAs	(26)	(28)
Other investing activities	7	(17)
Net cash provided from (used for) investing activities	(889)	2,454
Financing Activities:
Increase (decrease) in notes payable, net		86
Increase (decrease) in notes payable, net	(685)
Proceeds —
Long-term debt	2,653	1,220
Common stock	52	224
Short-term borrowings	565	0
Redemptions and repurchases —
Long-term debt	(1,481)	(2,429)
Redemptions — Short-term borrowings	(100)	(1,750)
Distributions to noncontrolling interests	(48)	(36)
Payment of common stock dividends	(655)	(623)
Other financing activities	(116)	(45)
Net cash provided from (used for) financing activities	185	(3,353)
Net Change in Cash, Cash Equivalents, and Restricted Cash	190	(155)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1,978	1,519
Cash, Cash Equivalents, and Restricted Cash at End of Period	2,168	1,364
Cash paid (received) during the period for —
Interest, net of amounts capitalized	490	462
Income taxes, net	(16)	0
Accrued property additions at end of period	733	899
Right-of-use assets obtained under operating leases	24	15
Right-of-use assets obtained under finance leases	4	29
ALABAMA POWER CO
Operating Activities:
Net income	284	221
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	241	244
Deferred income taxes	10	0
Allowance for equity funds used during construction	(10)	(14)
Pension, postretirement, and other employee benefits	(25)	(18)
Settlement of asset retirement obligations	(46)	(18)
Other, net	20	26
Changes in certain current assets and liabilities —
-Receivables	93	105
-Prepayments	(80)	(78)
-Other current assets	(29)	19
-Accounts payable	(305)	(286)
-Accrued taxes	100	80
-Accrued compensation	(111)	(122)
-Retail fuel cost over recovery	47	2
-Other current liabilities	(12)	(11)
-Materials and supplies	(22)	(4)
Net cash provided from operating activities	155	146
Investing Activities:
Property additions	(340)	(390)
Nuclear decommissioning trust fund purchases	(81)	(68)
Nuclear decommissioning trust fund sales	81	68
Cost of removal, net of salvage	(15)	(16)
Change in construction payables, net	(65)	(95)
Other investing activities	(4)	(10)
Net cash provided from (used for) investing activities	(424)	(511)
Proceeds —
Capital contributions from parent company	610	1,232
Redemptions and repurchases —
Senior notes	0	(200)
Pollution control revenue bonds	(87)	0
Payment of common stock dividends	(239)	(211)
Other financing activities	(11)	(10)
Net cash provided from (used for) financing activities	273	811
Net Change in Cash, Cash Equivalents, and Restricted Cash	4	446
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	894	313
Cash, Cash Equivalents, and Restricted Cash at End of Period	898	759
Cash paid (received) during the period for —
Interest, net of amounts capitalized	92	89
Accrued property additions at end of period	135	176
Right-of-use assets obtained under operating leases	2	2
Right-of-use assets obtained under finance leases	1	0
GEORGIA POWER CO
Operating Activities:
Net income	331	311
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	396	287
Deferred income taxes	(73)	127
Pension, postretirement, and other employee benefits	(40)	(35)
Settlement of asset retirement obligations	(33)	(34)
Storm damage reserve accruals	53	7
Retail fuel cost over recovery – long-term	90	0
Other, net	(52)	(25)
Changes in certain current assets and liabilities —
-Receivables	22	91
-Other current assets	(15)	33
-Accounts payable	(69)	(166)
-Accrued taxes	(156)	(245)
-Accrued compensation	(87)	(67)
-Other current liabilities	(5)	10
-Customer refunds	(107)	32
-Fossil fuel stock	(42)	(41)
-Prepaid income taxes	0	(73)
Net cash provided from operating activities	213	212
Investing Activities:
Property additions	(849)	(875)
Nuclear decommissioning trust fund purchases	(173)	(129)
Nuclear decommissioning trust fund sales	167	124
Proceeds from dispositions and asset sales	142	7
Cost of removal, net of salvage	(34)	(58)
Other investing activities	(2)	(11)
Change in construction payables, net of joint owner portion	(46)	(38)
Net cash provided from (used for) investing activities	(795)	(980)
Financing Activities:
Increase (decrease) in notes payable, net	11
Increase (decrease) in notes payable, net		(19)
Proceeds —
Short-term borrowings	200	0
Senior notes	1,500	0
Capital contributions from parent company	500	27
FFB loan	0	835
Pollution control revenue bonds	53	343
Redemptions and repurchases —
FFB loan	(16)	0
Senior notes	(950)	0
Pollution control revenue bonds	(148)	(108)
Payment of common stock dividends	(385)	(394)
Other financing activities	(23)	(19)
Net cash provided from (used for) financing activities	742	665
Net Change in Cash, Cash Equivalents, and Restricted Cash	160	(103)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	52	112
Cash, Cash Equivalents, and Restricted Cash at End of Period	212	9
Cash paid (received) during the period for —
Interest, net of amounts capitalized	122	92
Accrued property additions at end of period	472	607
Right-of-use assets obtained under operating leases	10	4
Right-of-use assets obtained under finance leases	0	28
MISSISSIPPI POWER CO
Operating Activities:
Net income	32	37
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	44	50
Deferred income taxes	(4)	(8)
Settlement of asset retirement obligations	(3)	(8)
Other, net	4	4
Changes in certain current assets and liabilities —
-Receivables	14	11
-Other current assets	(10)	7
-Accounts payable	(24)	(38)
-Accrued taxes	(54)	(62)
-Accrued compensation	(19)	(22)
-Other current liabilities	3	6
Net cash provided from operating activities	(17)	(23)
Investing Activities:
Property additions	(50)	(45)
Change in construction payables, net	(10)	(8)
Payments pursuant to LTSAs	(5)	(5)
Other investing activities	(6)	(5)
Net cash provided from (used for) investing activities	(71)	(63)
Proceeds —
Short-term borrowings	40	0
Capital contributions from parent company	75	0
Pollution control revenue bonds	0	43
Other long-term debt	100	0
Redemptions and repurchases —
Senior notes	(275)	0
Other financing activities	(1)	0
Return of capital to parent company	(37)	(38)
Net cash provided from (used for) financing activities	(98)	5
Net Change in Cash, Cash Equivalents, and Restricted Cash	(186)	(81)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	286	293
Cash, Cash Equivalents, and Restricted Cash at End of Period	100	212
Cash paid (received) during the period for —
Interest, net of amounts capitalized	18	13
Accrued property additions at end of period	25	27
SOUTHERN POWER CO
Operating Activities:
Net income	44	27
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	123	125
Deferred income taxes	(36)	17
(Gain) loss on dispositions, net	(39)	0
Other, net	(10)	(7)
Amortization of investment tax credits	(14)	(14)
Changes in certain current assets and liabilities —
-Receivables	5	10
-Other current assets	(2)	3
-Accounts payable	(34)	(32)
-Accrued taxes	8	5
-Other current liabilities	(13)	(15)
-Prepaid income taxes	51	(9)
Net cash provided from operating activities	83	110
Investing Activities:
Property additions	(47)	(66)
Proceeds from dispositions and asset sales	660	0
Change in construction payables, net	(15)	(7)
Payments pursuant to LTSAs	(15)	(15)
Other investing activities	17	9
Net cash provided from (used for) investing activities	600	(79)
Financing Activities:
Increase (decrease) in notes payable, net		5
Increase (decrease) in notes payable, net	(449)
Redemptions and repurchases —
Redemptions — Short-term borrowings	(100)	0
Distributions to noncontrolling interests	(48)	(36)
Capital contributions from noncontrolling interests	16	3
Payment of common stock dividends	(50)	(51)
Other financing activities	(1)	0
Net cash provided from (used for) financing activities	(632)	(79)
Net Change in Cash, Cash Equivalents, and Restricted Cash	51	(48)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	279	181
Cash, Cash Equivalents, and Restricted Cash at End of Period	330	133
Cash paid (received) during the period for —
Interest, net of amounts capitalized	28	28
Income taxes, net	(5)	1
Accrued property additions at end of period	27	19
SOUTHERN Co GAS
Operating Activities:
Net income	275	270
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	120	118
Deferred income taxes	22	42
Mark-to-market adjustments	13	45
Other, net	(19)	(20)
Changes in certain current assets and liabilities —
-Receivables	112	238
-Natural gas for sale	246	363
-Other current assets	33	59
-Accounts payable	(185)	(353)
-Accrued taxes	27	21
-Accrued compensation	(42)	(50)
-Other current liabilities	41	(50)
Net cash provided from operating activities	643	683
Investing Activities:
Property additions	(261)	(256)
Proceeds from dispositions and asset sales	178	0
Cost of removal, net of salvage	(15)	(12)
Change in construction payables, net	(18)	1
Investment in unconsolidated subsidiaries	(77)	(10)
Other investing activities	0	(13)
Net cash provided from (used for) investing activities	(193)	(290)
Financing Activities:
Increase (decrease) in notes payable, net	(39)	(289)
Redemptions and repurchases —
Payment of common stock dividends	(133)	(118)
Other financing activities	(13)	5
Net cash provided from (used for) financing activities	(185)	(402)
Net Change in Cash, Cash Equivalents, and Restricted Cash	265	(9)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	49	70
Cash, Cash Equivalents, and Restricted Cash at End of Period	314	61
Cash paid (received) during the period for —
Interest, net of amounts capitalized	49	55
Income taxes, net	(12)	(1)
Accrued property additions at end of period	$ 104	$ 98

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest capitalized	$ 20	$ 18
ALABAMA POWER CO
Interest capitalized	3	5
GEORGIA POWER CO
Interest capitalized	11	8
MISSISSIPPI POWER CO
Interest received	0	0
SOUTHERN POWER CO
Interest capitalized	4	4
SOUTHERN Co GAS
Interest capitalized	$ 2	$ 2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 2,164	$ 1,975
Receivables —
Customer accounts receivable	1,603	1,614
Energy marketing receivables	291	428
Unbilled revenues	522	599
Other accounts and notes receivable	560	817
Accumulated provision for uncollectible accounts	(53)	(49)
Materials and supplies	1,405	1,388
Fossil fuel for generation	577	521
Natural gas for sale	233	479
Prepaid expenses	667	314
Assets from risk management activities, net of collateral	134	183
Regulatory assets – asset retirement obligations	272	287
Other regulatory assets	876	885
Assets held for sale	0	188
Other current assets	179	188
Total current assets	9,430	9,817
Property, Plant, and Equipment:
In service	105,931	105,114
Less: Accumulated depreciation	31,180	30,765
Plant in service, net of depreciation	74,751	74,349
Nuclear fuel, at amortized cost	854	851
Construction work in progress	8,360	7,880
Total property, plant, and equipment	83,965	83,080
Other Property and Investments:
Goodwill	5,280	5,280
Equity investments in unconsolidated subsidiaries	1,386	1,303
Other intangible assets, net of amortization	523	536
Nuclear decommissioning trusts, at fair value	1,787	2,036
Leveraged leases	795	788
Miscellaneous property and investments	407	391
Total other property and investments	10,178	10,334
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,770	1,800
Deferred charges related to income taxes	798	798
Unamortized loss on reacquired debt	297	300
Regulatory assets – asset retirement obligations, deferred	4,384	4,094
Other regulatory assets, deferred	6,763	6,805
Assets held for sale, deferred	0	601
Other deferred charges and assets	1,267	1,071
Total deferred charges and other assets	15,279	15,469
Total Assets	118,852	118,700
Current Liabilities:
Securities due within one year	1,809	2,989
Notes payable	1,710	2,055
Energy marketing trade payables	298	442
Accounts payable —
Accounts payable	1,653	2,115
Customer deposits	491	496
Accrued taxes —
Accrued income taxes	25	0
Other accrued taxes	338	659
Accrued interest	414	474
Accrued compensation	502	992
Asset retirement obligations	514	504
Other regulatory liabilities	701	756
Liabilities held for sale	0	5
Operating lease obligations	230	229
Other current liabilities	868	830
Total current liabilities	9,553	12,546
Long-term Debt	44,235	41,798
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	8,398	7,888
Deferred credits related to income taxes	5,954	6,078
Accumulated deferred ITCs	2,271	2,291
Employee benefit obligations	1,778	1,814
Operating lease obligations, deferred	1,610	1,615
Asset retirement obligations, deferred	9,296	9,282
Accrued environmental remediation	230	234
Other cost of removal obligations	2,251	2,239
Other regulatory liabilities, deferred	368	256
Other deferred credits and liabilities	701	609
Total deferred credits and other liabilities	32,857	32,306
Total Liabilities	86,645	86,650
Redeemable Preferred Stock of Subsidiaries	291	291
Total stockholders' equity	31,916	31,759
Total Liabilities and Stockholders' Equity	118,852	118,700
ALABAMA POWER CO
Current Assets:
Cash and cash equivalents	898	894
Receivables —
Customer accounts receivable	377	425
Unbilled revenues	117	134
Other accounts and notes receivable	41	72
Accumulated provision for uncollectible accounts	(19)	(22)
Affiliated	40	37
Materials and supplies	531	512
Fossil fuel for generation	227	212
Prepaid expenses	119	50
Other regulatory assets	242	242
Other current assets	37	30
Total current assets	2,610	2,586
Property, Plant, and Equipment:
In service	30,348	30,023
Less: Accumulated depreciation	9,608	9,540
Plant in service, net of depreciation	20,740	20,483
Nuclear fuel, at amortized cost	290	296
Construction work in progress	777	890
Total property, plant, and equipment	21,807	21,669
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	64	66
Nuclear decommissioning trusts, at fair value	855	1,023
Miscellaneous property and investments	129	128
Total other property and investments	1,048	1,217
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	124	132
Deferred charges related to income taxes	243	244
Regulatory assets – asset retirement obligations, deferred	1,224	1,019
Other regulatory assets, deferred	1,968	1,976
Other deferred charges and assets	307	269
Deferred under recovered regulatory clause revenues	37	40
Total deferred charges and other assets	3,903	3,680
Total Assets	29,368	29,152
Current Liabilities:
Securities due within one year	296	251
Accounts payable —
Affiliated	212	316
Other	271	514
Customer deposits	101	100
Accrued taxes —
Other accrued taxes	168	78
Accrued interest	82	92
Accrued compensation	105	216
Asset retirement obligations	201	195
Other regulatory liabilities	155	193
Other current liabilities	109	105
Total current liabilities	1,700	2,060
Long-term Debt	8,141	8,270
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,283	3,260
Deferred credits related to income taxes	1,946	1,960
Accumulated deferred ITCs	99	100
Employee benefit obligations	198	206
Operating lease obligations, deferred	103	107
Asset retirement obligations, deferred	3,330	3,345
Other cost of removal obligations	402	412
Other regulatory liabilities, deferred	225	146
Other deferred credits and liabilities	41	40
Total deferred credits and other liabilities	9,627	9,576
Total Liabilities	19,468	19,906
Redeemable Preferred Stock	291	291
Total stockholders' equity	9,609	8,955
Total Liabilities and Stockholders' Equity	29,368	29,152
GEORGIA POWER CO
Current Assets:
Cash and cash equivalents	212	52
Receivables —
Customer accounts receivable	545	533
Unbilled revenues	195	203
Other accounts and notes receivable	44	209
Accumulated provision for uncollectible accounts	(2)	(2)
Affiliated	24	21
Joint owner accounts receivable	129	136
Materials and supplies	513	501
Fossil fuel for generation	315	272
Prepaid expenses	38	63
Regulatory assets – storm damage reserves	213	213
Regulatory assets – asset retirement obligations	235	254
Other regulatory assets	295	263
Other current assets	69	77
Total current assets	2,825	2,795
Property, Plant, and Equipment:
In service	38,436	38,137
Less: Accumulated depreciation	11,929	11,753
Plant in service, net of depreciation	26,507	26,384
Nuclear fuel, at amortized cost	563	555
Construction work in progress	6,187	5,650
Total property, plant, and equipment	33,257	32,589
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	52	52
Nuclear decommissioning trusts, at fair value	932	1,013
Miscellaneous property and investments	65	64
Total other property and investments	1,049	1,129
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,401	1,428
Deferred charges related to income taxes	519	519
Regulatory assets – asset retirement obligations, deferred	2,970	2,865
Other regulatory assets, deferred	2,677	2,716
Other deferred charges and assets	481	500
Total deferred charges and other assets	8,048	8,028
Total Assets	45,179	44,541
Current Liabilities:
Securities due within one year	74	1,025
Notes payable	451	365
Accounts payable —
Affiliated	389	512
Other	723	711
Customer deposits	284	283
Accrued taxes —
Other accrued taxes	239	407
Accrued interest	97	118
Accrued compensation	120	233
Asset retirement obligations	272	265
Other regulatory liabilities	342	447
Operating lease obligations	147	144
Other current liabilities	233	187
Total current liabilities	3,371	4,697
Long-term Debt	12,297	10,791
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,255	3,257
Deferred credits related to income taxes	2,792	2,862
Accumulated deferred ITCs	253	255
Employee benefit obligations	497	540
Operating lease obligations, deferred	1,280	1,282
Asset retirement obligations, deferred	5,547	5,519
Other deferred credits and liabilities	375	273
Total deferred credits and other liabilities	13,999	13,988
Total Liabilities	29,667	29,476
Total stockholders' equity	15,512	15,065
Total Liabilities and Stockholders' Equity	45,179	44,541
MISSISSIPPI POWER CO
Current Assets:
Cash and cash equivalents	100	286
Receivables —
Customer accounts receivable	32	35
Unbilled revenues	33	39
Other accounts and notes receivable	23	26
Affiliated	25	27
Materials and supplies	59	61
Fossil fuel for generation	24	26
Other regulatory assets	85	99
Other current assets	10	10
Total current assets	391	609
Property, Plant, and Equipment:
In service	4,900	4,857
Less: Accumulated depreciation	1,489	1,463
Plant in service, net of depreciation	3,411	3,394
Construction work in progress	127	126
Total property, plant, and equipment	3,538	3,520
Other Property and Investments:
Total other property and investments	131	131
Deferred Charges and Other Assets:
Deferred charges related to income taxes	32	32
Regulatory assets – asset retirement obligations, deferred	197	210
Other regulatory assets, deferred	386	360
Other deferred charges and assets	48	34
Accumulated deferred income taxes	137	139
Total deferred charges and other assets	800	775
Total Assets	4,860	5,035
Current Liabilities:
Securities due within one year	7	281
Notes payable	40	0
Accounts payable —
Affiliated	62	76
Other	56	75
Accrued taxes —
Other accrued taxes	51	105
Accrued interest	14	15
Accrued compensation	16	35
Asset retirement obligations	28	33
Other regulatory liabilities	54	21
Other current liabilities	69	64
Over recovered regulatory clause liabilities	32	29
Total current liabilities	429	734
Long-term Debt	1,406	1,308
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	422	424
Deferred credits related to income taxes	320	352
Employee benefit obligations	98	99
Asset retirement obligations, deferred	158	157
Other cost of removal obligations	192	189
Other regulatory liabilities, deferred	71	76
Other deferred credits and liabilities	42	44
Total deferred credits and other liabilities	1,303	1,341
Total Liabilities	3,138	3,383
Total stockholders' equity	1,722	1,652
Total Liabilities and Stockholders' Equity	4,860	5,035
SOUTHERN POWER CO
Current Assets:
Cash and cash equivalents	330	279
Receivables —
Customer accounts receivable	109	107
Other accounts and notes receivable	54	73
Affiliated	26	30
Materials and supplies	198	191
Other current assets	24	43
Prepaid income taxes	452	36
Total current assets	1,193	759
Property, Plant, and Equipment:
In service	13,282	13,270
Less: Accumulated depreciation	2,580	2,464
Plant in service, net of depreciation	10,702	10,806
Construction work in progress	534	515
Total property, plant, and equipment	11,236	11,321
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	45	28
Miscellaneous property and investments	45	28
Intangible assets, net of amortization	317	322
Total other property and investments	362	350
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	368	369
Assets held for sale, deferred	0	601
Other deferred charges and assets	216	216
Prepaid LTSAs	134	128
Accumulated deferred income taxes	129	551
Income taxes receivable, non-current	8	5
Total deferred charges and other assets	855	1,870
Total Assets	13,646	14,300
Current Liabilities:
Securities due within one year	824	824
Notes payable	0	549
Accounts payable —
Affiliated	43	56
Other	59	85
Accrued taxes —
Accrued income taxes	9	0
Other accrued taxes	20	26
Accrued interest	36	32
Other current liabilities	119	132
Total current liabilities	1,110	1,704
Long-term Debt	3,545	3,574
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	114	115
Accumulated deferred ITCs	1,717	1,731
Operating lease obligations, deferred	375	376
Other deferred credits and liabilities	234	178
Total deferred credits and other liabilities	2,440	2,400
Total Liabilities	7,095	7,678
Total stockholders' equity	6,551	6,622
Total Liabilities and Stockholders' Equity	13,646	14,300
SOUTHERN Co GAS
Current Assets:
Cash and cash equivalents	311	46
Receivables —
Customer accounts receivable	407	323
Energy marketing receivables	291	428
Unbilled revenues	136	183
Other accounts and notes receivable	102	114
Accumulated provision for uncollectible accounts	(25)	(18)
Affiliated	3	5
Natural gas for sale	233	479
Prepaid expenses	53	65
Assets from risk management activities, net of collateral	119	177
Other regulatory assets	69	92
Assets held for sale	0	171
Other current assets	43	41
Total current assets	1,742	2,106
Property, Plant, and Equipment:
In service	16,456	16,344
Less: Accumulated depreciation	4,651	4,650
Plant in service, net of depreciation	11,805	11,694
Construction work in progress	680	613
Total property, plant, and equipment	12,485	12,307
Other Property and Investments:
Goodwill	5,015	5,015
Equity investments in unconsolidated subsidiaries	1,333	1,251
Other intangible assets, net of amortization	65	70
Miscellaneous property and investments	20	20
Total other property and investments	6,433	6,356
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	91	93
Other regulatory assets, deferred	605	618
Other deferred charges and assets	261	207
Total deferred charges and other assets	957	918
Total Assets	21,617	21,687
Current Liabilities:
Notes payable	611	650
Energy marketing trade payables	298	442
Accounts payable —
Affiliated	39	41
Other	258	315
Customer deposits	89	96
Accrued taxes —
Accrued income taxes	37	0
Other accrued taxes	61	71
Accrued interest	64	52
Accrued compensation	58	100
Other regulatory liabilities	149	94
Other current liabilities	121	128
Liabilities from risk management activities, net of collateral	41	21
Total current liabilities	1,826	2,010
Long-term Debt	5,836	5,845
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	1,235	1,219
Deferred credits related to income taxes	867	874
Employee benefit obligations	252	265
Operating lease obligations, deferred	76	78
Accrued environmental remediation	230	233
Other cost of removal obligations	1,625	1,606
Other deferred credits and liabilities	39	51
Total deferred credits and other liabilities	4,324	4,326
Total Liabilities	11,986	12,181
Total stockholders' equity	9,631	9,506
Total Liabilities and Stockholders' Equity	$ 21,617	$ 21,687

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Other intangible assets, amortization	$ 292	$ 280
SOUTHERN POWER CO
Other intangible assets, amortization	74	69
SOUTHERN Co GAS
Other intangible assets, amortization	$ 181	$ 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 COPaid-In Capital	SOUTHERN POWER CORetained Earnings (Accumulated Deficit)	SOUTHERN POWER COAccumulated Other Comprehensive Income (Loss)	SOUTHERN POWER COTotal Common Stockholders' Equity	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	$ 1,600	$ 1,352	$ 16	$ 2,968	$ 4,316	$ 8,570	$ 8,856	$ (312)	$ 26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,084				2,084			217			217		311			311		37			37		56		56		56		270		270
Stock issued (in shares)		6
Stock issued	224	$ 28		196
Stock-based compensation	24			24
Cash dividends on common stock	(622)				(622)			(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)
Net income (loss) attributable to noncontrolling interests	(29)						(29)																(29)					(29)
Other	5		$ (2)	7	(1)	0	1						(1)		(1)		0						(1)	(1)	(1)	0	(2)	1
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)
Return of capital to parent company																		(38)		(38)
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	1,600	1,356	12	2,968	4,250	8,738	8,873	(160)	25
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	909	1,485	(26)	2,368	4,254	9,506	9,697	(198)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	868				868			280			280		331			331		32			32		75		75		75		275		275
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)
Net income (loss) attributable to noncontrolling interests	(31)						(31)																(31)					(31)
Other	(3)	$ 0	$ (2)	0	(2)	1	0											(1)		(1)
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)
Return of capital to parent company																		(37)		(37)									(2)	(2)
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	$ 909	$ 1,510	$ (59)	$ 2,360	$ 4,191	$ 9,631	$ 9,695	$ (56)	$ (8)

Consolidated Statements of St_2

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

INTRODUCTION

INTRODUCTION	3 Months Ended
	Mar. 31, 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 March 31, 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, 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 March 31, 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 could continue to disrupt supply chains and capital markets, 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 March 31, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Intangible Assets, Net Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (121 ) $ 91 $ 212 $ (116 ) $ 96 Trade names 64 (26 ) 38 64 (25 ) 39 Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 PPA fair value adjustments 390 (74 ) 316 390 (69 ) 321 Other 10 (8 ) 2 11 (8 ) 3 Total other intangible assets subject to amortization $ 740 $ (292 ) $ 448 $ 741 $ (280 ) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (292 ) $ 523 $ 816 $ (280 ) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (74 ) $ 316 $ 390 $ (69 ) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (108 ) $ 48 $ 156 $ (104 ) $ 52 Trade names 26 (10 ) 16 26 (10 ) 16 Wholesale gas services Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 Total other intangible assets subject to amortization $ 246 $ (181 ) $ 65 $ 246 $ (176 ) $ 70 Amortization associated with other intangible assets was as follows: Three Months Ended March 31, 2020 (in millions) Southern Company (a) $ 12 Southern Power (b) $ 5 Southern Company Gas Gas marketing services $ 4 Wholesale gas services (b) 1 Southern Company Gas total $ 5 (a) Includes $6 million for the three months ended March 31, 2020 , 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 March 31, 2020 and/or December 31, 2019 : Southern Company Southern Company Gas At March 31, 2020 At December 31, 2019 At March 31, 2020 At December 31, 2019 (in millions) (in millions) Cash and cash equivalents $ 2,164 $ 1,975 $ 311 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — 3 Other current assets 3 — 3 — Total cash, cash equivalents, and restricted cash $ 2,168 (b) $ 1,978 $ 314 $ 49 (a) Represents restricted cash held by Southern Company Gas as collateral for workers' compensation, life insurance, and long-term disability insurance. (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. Southern Company Gas had no material adjustments for any period presented. 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. Nicor Gas' inventory decrement at March 31, 2020 is expected to be restored prior to year end. 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 months ended March 31, 2020 and is expected to result in an immaterial decrease in annual depreciation for 2020.

REGULATORY MATTERS

REGULATORY MATTERS	3 Months Ended
	Mar. 31, 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 March 31, 2020 and December 31, 2019 were as follows: Regulatory Clause Balance Sheet Line Item March 31, December 31, (in millions) Alabama Power Rate CNP Compliance Other regulatory liabilities, current $ 35 $ 55 Other regulatory liabilities, deferred 17 7 Rate CNP PPA Deferred under recovered regulatory clause revenues 37 40 Retail Energy Cost Recovery Other regulatory liabilities, current 74 32 Other regulatory liabilities, deferred 22 17 Natural Disaster Reserve Other regulatory liabilities, current 27 37 Other regulatory liabilities, deferred 104 113 Georgia Power Fuel Cost Recovery Other current liabilities $ 6 $ — Other deferred credits and liabilities 163 73 Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 25 $ 23 Ad Valorem Tax Other regulatory assets 11 47 Other regulatory assets, deferred 38 — Property Damage Reserve Other regulatory liabilities, deferred 53 54 Southern Company Gas Natural Gas Cost Recovery Other regulatory liabilities $ 84 $ 74 Alabama Power Petition for Certificate of Convenience and Necessity During March 2020, a hearing was held before the Alabama PSC regarding Alabama Power's petition for a certificate of convenience and necessity (CCN) to procure additional capacity, including the Autauga Combined Cycle Acquisition. On April 22, 2020, the FERC approved the Autauga Combined Cycle Acquisition. The Autauga Combined Cycle Acquisition, as well as procurement of the other resources identified in Alabama Power's CCN petition, remain subject to approval by the Alabama PSC. The ultimate outcome of this matter cannot be determined at this time. Georgia Power Deferral of Incremental COVID-19 Costs On April 7, 2020, in response to the COVID-19 pandemic, the Georgia PSC approved an order directing Georgia Power to continue its previous, voluntary suspension of customer disconnections and to defer the resulting incremental bad debt and other incremental costs as a regulatory asset. Georgia Power and the staff of the Georgia PSC will work collaboratively to establish a methodology for identifying these incremental costs. The period over which such costs will be recovered is expected to be determined in Georgia Power's next base rate case. At March 31, 2020, the incremental costs deferred were immaterial. 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. The ultimate outcome of this matter cannot be determined at this time. Fuel Cost Recovery On March 9, 2020, Georgia Power filed a request with the Georgia PSC to decrease fuel rates by 16% effective June 1, 2020, which is expected to reduce annual billings by approximately $329 million . Georgia Power expects the Georgia PSC to make a final decision on this matter on May 28, 2020. The ultimate outcome of this matter cannot be determined at this time. Nuclear Construction In 2009, the Georgia PSC certified construction of Plant Vogtle Units 3 and 4. Georgia Power holds a 45.7% ownership interest in Plant Vogtle Units 3 and 4. 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) $ 8.2 Construction contingency estimate 0.2 Total project capital cost forecast (a)(b) 8.4 Net investment as of March 31, 2020 (b) (6.2 ) Remaining estimate to complete (a) $ 2.2 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $270 million , of which $36 million had been accrued through March 31, 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 $3.1 billion , of which $2.3 billion had been incurred through March 31, 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 commodity installation, system turnovers, and workforce statistics. During the first quarter 2020, approximately $66 million of the $366 million construction contingency estimate established in the second quarter 2018 was allocated to the base capital cost forecast for cost risks including, among other things, construction productivity, field support, subcontracts, and procurement, as well as the impacts of the April 2020 reduction in workforce described below. Through March 31, 2020 , a total of approximately $206 million of the $366 million construction contingency estimate established in the second quarter 2018 has been allocated to the base capital cost forecast for cost risks including, among other factors, construction productivity, including the April 2020 reduction in workforce 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. As and when construction contingency is spent, Georgia Power may request the Georgia PSC to evaluate those expenditures for rate recovery. 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 closure rates for work packages, 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 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 aggressive site work plan relies on meeting increased monthly production and activity target values during 2020. Through March 2020, Unit 3 mechanical, electrical, and subcontract activities started to build a backlog; however, overall production was generally consistent with the updated aggressive site work plan. 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. Multiple members of the workforce have tested positive for COVID-19. The COVID-19 pandemic has impacted productivity levels and pace of activity completion. On April 15, 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 expected to total approximately 20% of the existing 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 ongoing challenges with labor productivity that have been exacerbated by the impact of the COVID-19 pandemic. It is expected to provide operational efficiencies by increasing productivity of the remaining workforce and reducing workforce fatigue and absenteeism. It is also expected to allow for increased social distancing by the workforce and facilitate compliance with the latest recommendations from the Centers for Disease Control and Prevention. To meet the 2020 targets in the aggressive site work plan for both Unit 3 and Unit 4, construction productivity, including subcontractors, must improve and be sustained above historical average levels. In addition, appropriate levels of craft laborers, particularly electrical and pipefitter craft labor, must be maintained. The workforce levels resulting from the April 2020 reduction are expected to last at least through the summer as Georgia Power continues to monitor the impacts of the COVID-19 pandemic on the construction site. Georgia Power's proportionate share of the estimated incremental cost of this mitigation action, which is currently estimated to total approximately $20 million and is included in the first quarter 2020 contingency allocation, assumes absenteeism rates normalize and the intended productivity efficiencies are realized in the coming months. Based on these assumptions, while this mitigation action has extended and may further extend certain milestone dates in the updated aggressive site work plan, Georgia Power does not expect it to affect either the total project capital cost forecast or the ability 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 and mechanical 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; regional transmission upgrades; 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. 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 April 20, 2020, Nuclear Watch South filed a request for hearing and contention with the NRC that challenges the closure of certain ITAAC. 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 March 31, 2020 , Georgia Power had recovered approximately $2.3 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. In December 2019, the Georgia PSC approved Georgia Power's request to decrease the NCCR tariff by $62 million annually, effective January 1, 2020. 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 include carrying costs on those capital costs deemed prudent in the Vogtle Cost Settlement Agreement. The January 11, 2018 order also stated that if Plant Vogtle Units 3 and 4 are not commercially operational by June 1, 2021 and June 1, 2022, respectively, the ROE used to calculate the NCCR tariff will be further reduced by 10 basis points each month (but not lower than Georgia Power's average cost of long-term debt) until the respective Unit is commercially operational. The ROE reductions negatively impacted earnings by approximately $75 million in 2019 and are estimated to have negative earnings impacts of approximately $145 million , $255 million , and $200 million in 2020, 2021, and 2022, respectively. In its January 11, 2018 order, the Georgia PSC also stated if other conditions change and assumptions upon which Georgia Power's seventeenth VCM report are based do not materialize, the Georgia PSC reserved the right to reconsider the decision to continue construction. In February 2018, Georgia Interfaith Power & Light, Inc. (GIPL) and Partnership for Southern Equity, Inc. (PSE) filed a petition appealing the Georgia PSC's January 11, 2018 order with the Fulton County Superior Court. In March 2018, Georgia Watch filed a similar appeal to the Fulton County Superior Court for judicial review of the Georgia PSC's decision and denial of Georgia Watch's motion for reconsideration. In December 2018, the Fulton County Superior Court granted Georgia Power's motion to dismiss the two appeals. In January 2019, GIPL, PSE, and Georgia Watch filed an appeal of this decision with the Georgia Court of Appeals. In October 2019, the Georgia Court of Appeals issued an opinion affirming the Fulton County Superior Court's ruling that the Georgia PSC's January 11, 2018 order was not a final, appealable decision. In addition, the Georgia Court of Appeals remanded the case to the Fulton County Superior Court to clarify its ruling as to whether the petitioners showed that review of the Georgia PSC's final order would not provide them an adequate remedy. On April 21, 2020, the Fulton County Superior Court entered an appealable order granting Georgia Power's motion to dismiss the two appeals. Georgia Power believes the petitions have no merit; however, an adverse outcome in the litigation combined with subsequent adverse action by the Georgia PSC could have a material impact on Southern Company's and Georgia Power's results of operations, financial condition, and liquidity. The Georgia PSC has approved 21 VCM reports covering the periods through June 30, 2019, including total construction capital costs incurred through that date of $6.7 billion (before $1.7 billion of payments received under the Guarantee Settlement Agreement and approximately $188 million in related customer refunds). On February 19, 2020, Georgia Power filed its twenty-second VCM report with the Georgia PSC covering the period from July 1, 2019 through December 31, 2019, requesting approval of $674 million of construction capital costs incurred during that period. The ultimate outcome of these matters cannot be determined at this time. Mississippi Power 2019 Base Rate Case On March 17, 2020, the Mississippi PSC approved a settlement agreement between Mississippi Power and the Mississippi Public Utilities Staff related to Mississippi Power's base rate case filed in November 2019 (Mississippi Power Rate Case Settlement Agreement). Under the terms of the Mississippi Power Rate Case Settlement Agreement, annual retail rates decreased approximately $16.7 million , or 1.85% , effective for the first billing cycle of April 2020, based on a test year period of January 1, 2020 through December 31, 2020, a 53% average equity ratio, an allowed maximum actual equity ratio of 55% by the end of 2020, and a 7.57% return on investment. Additionally, the approved Mississippi Power Rate Case Settlement Agreement: (i) established common amortization periods of four years for regulatory assets and three years for regulatory liabilities included in the approved revenue requirement, including those related to unprotected deferred income taxes; (ii) established new depreciation rates reflecting an annual increase in depreciation of approximately $10 million ; and (iii) excluded certain compensation costs totaling approximately $3.9 million . It also eliminated separate rates for costs associated with Plant Ratcliffe and energy efficiency initiatives and includes such costs in the PEP, ECO Plan, and ad valorem tax adjustment factor, as applicable. In accordance with the previous order of the Mississippi PSC suspending the operation of PEP and the ECO Plan for 2018 through 2020, Mississippi Power plans to resume PEP proceedings and ECO Plan filings for 2021. Performance Evaluation Plan Under the Mississippi Power Rate Case Settlement Agreement, Mississippi Power is required to file with the Mississippi PSC PEP compliance rate clauses to incorporate Mississippi Power's and the Mississippi Public Utilities Staff's recommended revisions to PEP by May 18, 2020. These revisions include, but are not limited to, changing the filing date for the annual PEP rate filing from November of the immediately preceding year to March of the current year, utilizing a historic test year adjusted for "known and measurable" changes, using discounted cash flow and regression formulas to determine base return on equity, and moving all embedded ad valorem property taxes currently collected in PEP to the ad valorem tax adjustment clause. These revisions are subject to the approval of the Mississippi PSC. The ultimate outcome of this matter cannot be determined at this time. Deferral of Incremental COVID-19 Costs On April 14, 2020, in order to mitigate the economic impact of the COVID-19 pandemic on customers, the Mississippi PSC approved an order directing Mississippi Power to continue its previous, voluntary suspension of customer disconnections and to defer as a regulatory asset all necessary and reasonable incremental costs or expenses to plan, prepare, stage, or react to protect and keep safe its employees and customers, and to reliably operate its utility system during the COVID-19 pandemic. The period over which such costs will be recovered is expected to be determined in Mississippi Power's next PEP filing. At March 31, 2020, the incremental costs deferred were immaterial. The ultimate outcome of this matter cannot be determi

CONTINGENCIES

CONTINGENCIES	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
CONTINGENCIES	CONTINGENCIES See 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 against Southern Company, certain of its officers, and certain former Mississippi Power officers 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 alleges that Southern Company, certain of its officers, and certain former Mississippi Power officers 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 at least June 15, 2020. 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 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. 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 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. 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 tort law claims. In 2016, the Georgia Court of Appeals reversed the trial court's previous dismissal of the case and remanded the case to the trial court. Georgia Power filed a petition for writ of certiorari with the Georgia Supreme Court, which was granted in 2017. In 2018, the Georgia Supreme Court affirmed the judgment of the Georgia Court of Appeals and remanded the case to the trial court for further proceedings. 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 to address certain terms the court previously held were ambiguous as used in the Georgia PSC's orders. The order entered by the Superior Court of Fulton County 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. In October 2019, the Georgia PSC issued an order that found and concluded that 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 the entry of a detailed order addressing each class certification factor. 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. 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. An adverse outcome in this proceeding could have a material impact on Southern Company's and Mississippi Power's financial statements. In November 2018, Ray C. Turnage and 10 other individual plaintiffs filed a putative class action complaint against Mississippi Power and three 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 under a cause of action 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. Mississippi Power's motion to dismiss the first amended complaint filed in 2019 remains pending before the court. 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 March 31, 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 $262 million and $269 million as of March 31, 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. Other Matters 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. D ismantlement of the abandoned gasifier-related assets and site restoration activities are expected to be completed in 2024. 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, are estimated to total $17 million for the remainder of 2020, $15 million to $17 million annually in 2021 through 2023, and $5 million in 2024. In addition, closure costs for the mine and gasifier-related assets, currently estimated at up to $10 million pre-tax (excluding dismantlement costs, net of salvage), may be incurred during the remainder of 2020. In 2018, Mississippi Power filed with the DOE its request for property closeout certification under the contract related to the $387 million of grants received for the Kemper County energy facility. Mississippi Power expects to close out the DOE contract in 2020. 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 Kemper County energy facility. 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 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. 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 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 cancellation, any of which could result in impairment of Southern Company Gas' investment and could have a significant impact on Southern Company's financial statements and a material impact on Southern Company Gas' financial statements. Alabama Power On April 22, 2020, the FERC approved the Autauga Combined Cycle Acquisition. The Autauga Combined Cycle Acquisition remains subject to approval by the Alabama PSC. See Note (B) under "Alabama Power" for additional information. The ultimate outcome of this matter cannot be determined at this time.

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME	3 Months Ended
	Mar. 31, 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 tables disaggregate revenue from contracts with customers for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating revenues Retail electric revenues Residential $ 1,370 $ 553 $ 760 $ 57 $ — $ — Commercial 1,146 364 720 62 — — Industrial 680 321 281 78 — — Other 23 5 16 2 — — Total retail electric revenues 3,219 1,243 1,777 199 — — Natural gas distribution revenues Residential 496 — — — — 496 Commercial 130 — — — — 130 Transportation 264 — — — — 264 Industrial 12 — — — — 12 Other 97 — — — — 97 Total natural gas distribution revenues 999 — — — — 999 Wholesale electric revenues PPA energy revenues 159 27 9 2 125 — PPA capacity revenues 105 27 12 1 66 — Non-PPA revenues 51 19 2 69 58 — Total wholesale electric revenues 315 73 23 72 249 — Other natural gas revenues Wholesale gas services 396 — — — — 396 Gas marketing services 163 — — — — 163 Other natural gas revenues 7 — — — — 7 Total natural gas revenues 566 — — — — 566 Other revenues 192 37 95 5 3 — Total revenue from contracts with customers 5,291 1,353 1,895 276 252 1,565 Other revenue sources (a) 868 (2 ) (70 ) 1 123 825 Other adjustments (b) (1,141 ) — — — — (1,141 ) Total operating revenues $ 5,018 $ 1,351 $ 1,825 $ 277 $ 375 $ 1,249 (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. Three Months Ended March 31, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating revenues Retail electric revenues Residential $ 1,327 $ 559 $ 708 $ 60 $ — $ — Commercial 1,125 368 692 65 — — Industrial 708 338 296 74 — — Other 21 6 11 4 — — Total retail electric revenues 3,181 1,271 1,707 203 — — Natural gas distribution revenues Residential 601 — — — — 601 Commercial 170 — — — — 170 Transportation 256 — — — — 256 Industrial 17 — — — — 17 Other 116 — — — — 116 Total natural gas distribution revenues 1,160 — — — — 1,160 Wholesale electric revenues PPA energy revenues 190 31 12 3 151 — PPA capacity revenues 107 27 13 1 81 — Non-PPA revenues 55 60 2 74 41 — Total wholesale electric revenues 352 118 27 78 273 — Other natural gas revenues Wholesale gas services 721 — — — — 721 Gas marketing services 221 — — — — 221 Other natural gas revenues 10 — — — — 10 Total natural gas revenues 952 — — — — 952 Other revenues 266 46 92 5 4 — Total revenue from contracts with customers 5,911 1,435 1,826 286 277 2,112 Other revenue sources (a) 1,361 (27 ) 7 1 166 1,222 Other adjustments (b) (1,860 ) — — — — (1,860 ) Total operating revenues $ 5,412 $ 1,408 $ 1,833 $ 287 $ 443 $ 1,474 (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 Contract Balances The following table reflects the closing balances of receivables, contract assets, and contract liabilities related to revenues from contracts with customers at March 31, 2020 and December 31, 2019 : Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Accounts Receivables As of March 31, 2020 $ 2,224 $ 518 $ 697 $ 70 $ 86 $ 696 As of December 31, 2019 2,413 586 688 79 97 749 Contract Assets As of March 31, 2020 $ 100 $ — $ 53 $ 3 $ — $ — As of December 31, 2019 117 — 69 — — — Contract Liabilities As of March 31, 2020 $ 49 $ 7 $ 11 $ — $ 1 $ 1 As of December 31, 2019 52 10 13 — 1 1 As of March 31, 2020 and December 31, 2019 , Georgia Power had contract assets primarily related to unregulated service agreements, where payment is contingent on project completion, and 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 the one-year contract term. Alabama Power had contract liabilities for outstanding performance obligations primarily related to extended service agreements. Contract liabilities for Georgia Power and Southern Power relate to cash collections recognized in advance of revenue for certain unregulated service agreements and certain levelized PPAs, respectively. Southern Company's unregulated distributed generation business had $36 million and $40 million of contract assets and $29 million and $28 million of contract liabilities at March 31, 2020 and December 31, 2019 , respectively, for outstanding performance obligations. Revenues recognized in the three months ended March 31, 2020 , which were included in contract liabilities at December 31, 2019 , were immaterial for the 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 March 31, 2020 are expected to be recognized as follows: 2020 (remaining) 2021 2022 2023 2024 2025 and Thereafter (in millions) Southern Company $ 367 $ 416 $ 354 $ 334 $ 314 $ 2,164 Alabama Power 23 33 31 24 7 5 Georgia Power 52 66 36 34 23 61 Southern Power 224 285 287 277 285 2,116 Revenue expected to be recognized for performance obligations remaining at March 31, 2020 was immaterial for Mississippi Power. Lease Income Lease income for the three months ended March 31, 2020 and 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended March 31, 2020 Lease income - interest income on sales-type leases $ 3 $ — $ — $ 3 $ — $ — Lease income - operating leases 51 6 16 — 24 9 Variable lease income 74 — — — 80 — Total lease income $ 128 $ 6 $ 16 $ 3 $ 104 $ 9 For the Three Months Ended March 31, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 71 7 19 — 46 9 Variable lease income 66 — — — 75 — Total lease income $ 139 $ 7 $ 19 $ 2 $ 121 $ 9 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.

CONSOLIDATED ENTITIES AND EQUIT

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS	3 Months Ended
	Mar. 31, 2020
Regulated Operations [Abstract]
CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS	CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS See 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 March 31, 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 and $381 million , respectively. Noncontrolling interests totaled $1.1 billion at both March 31, 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 March 31, 2020 and December 31, 2019 , SP Wind had total assets of $2.5 billion and total liabilities of $123 million and $128 million , respectively. Noncontrolling interests totaled $45 million at both March 31, 2020 and December 31, 2019 . 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 March 31, 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 $396 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 March 31, 2020 and December 31, 2019 , Southern Power had equity method investments in several wind and battery storage projects totaling $45 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 March 31, 2020 and December 31, 2019 and related income from those investments for the three -month periods ended March 31, 2020 and 2019 were as follows: Investment Balance March 31, 2020 December 31, 2019 (a) (in millions) SNG (b) $ 1,216 $ 1,137 PennEast Pipeline (c) 85 82 Other 32 32 Total $ 1,333 $ 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 March 31, 2020 Three Months Ended March 31, 2019 (in millions) SNG $ 37 $ 42 Atlantic Coast Pipeline (*) 3 3 PennEast Pipeline (*) 2 2 Other 1 1 Total $ 43 $ 48 (*) Amounts primarily result from AFUDC equity recorded by the project entity . SNG Selected financial information of SNG for the three months ended March 31, 2020 and 2019 is as follows: Income Statement Information Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 (in millions) Revenues $ 158 $ 166 Operating income 98 106 Net income 75 84

FINANCING

FINANCING	3 Months Ended
	Mar. 31, 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 March 31, 2020 , committed credit arrangements with banks were as follows: Expires Company 2020 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 1,733 — Mississippi Power — 150 125 — 275 210 — 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 $ 7,636 $ 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 $25 million and $60 million , respectively, was unused at March 31, 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 March 31, 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 March 31, 2020 was approximately $1.4 billion (comprised of approximately $854 million at Alabama Power, $550 million at Georgia Power, and $40 million at Mississippi Power). Subsequent to March 31, 2020, Mississippi Power purchased and held or redeemed all $40 million of its variable rate revenue bonds. In addition, at March 31, 2020 , Georgia Power had approximately $188 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, as a result of stock price volatility in the first quarter 2020, 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 March 31, 2020 Three Months Ended March 31, 2019 (in millions) As reported shares 1,057 1,038 Effect of stock-based compensation 7 7 Effect of equity units 3 — Diluted shares 1,067 1,045 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 months ended March 31, 2020 . There were no such amounts for the three months ended March 31, 2019 .

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 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 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 14.7% for the three months ended March 31, 2020 compared to 39.8% 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. 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 4.6% for the three months ended March 31, 2020 compared to 20.8% 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. See Note 2 to the financial statements under "Georgia Power" in Item 8 of the Form 10-K for additional information. Southern Power Southern Power's effective tax rate was 13.5% for the three months ended March 31, 2020 compared to a benefit rate of (49.8)% for the corresponding period in 2019 . The effective tax rate increase was primarily due to the tax impact from the sale of Plant Mankato in 2020. See Note (K) under "Southern Power" for additional information.

RETIREMENT BENEFITS

RETIREMENT BENEFITS	3 Months Ended
	Mar. 31, 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 months ended March 31, 2020 and 2019 are presented in the following tables. Three Months Ended March 31, 2020 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 94 $ 22 $ 24 $ 4 $ 2 $ 8 Interest cost 108 25 33 5 1 8 Expected return on plan assets (275 ) (66 ) (87 ) (13 ) (3 ) (19 ) Amortization: Prior service costs 1 — — — — (1 ) Regulatory asset — — — — — 4 Net (gain)/loss 67 18 22 3 1 2 Net periodic pension cost (income) $ (5 ) $ (1 ) $ (8 ) $ (1 ) $ 1 $ 2 Postretirement Benefits Service cost $ 5 $ 2 $ 1 $ — $ — $ — Interest cost 13 3 5 — — 2 Expected return on plan assets (18 ) (7 ) (7 ) — — (2 ) Amortization: Regulatory asset — — — — — 2 Net (gain)/loss 1 — 1 — — (1 ) Net periodic postretirement benefit cost $ 1 $ (2 ) $ — $ — $ — $ 1 Three Months Ended March 31, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 73 $ 17 $ 19 $ 3 $ 2 $ 6 Interest cost 123 28 39 6 1 9 Expected return on plan assets (221 ) (51 ) (73 ) (10 ) (2 ) (15 ) Amortization: Prior service costs — — — — — (1 ) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (4 ) $ — $ 1 $ 3 Postretirement Benefits Service cost $ 5 $ 1 $ 1 $ — $ — $ 1 Interest cost 17 4 7 1 — 2 Expected return on plan assets (16 ) (6 ) (6 ) — — (2 ) Amortization: Prior service costs 1 1 — — — — Regulatory asset — — — — — 2 Net (gain)/loss (1 ) — — — — (1 ) Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS As of March 31, 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 March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Southern Company Assets: Energy-related derivatives (a) $ 328 $ 164 $ 87 $ — $ 579 Interest rate derivatives — 22 — — 22 Investments in trusts: (b)(c) Domestic equity 578 108 — — 686 Foreign equity 52 171 — — 223 U.S. Treasury and government agency securities — 289 — — 289 Municipal bonds — 103 — — 103 Pooled funds – fixed income — 16 — — 16 Corporate bonds 23 297 — — 320 Mortgage and asset backed securities — 85 — — 85 Private equity — — — 60 60 Other 24 5 — — 29 Cash equivalents 1,686 11 — — 1,697 Other investments 9 29 — — 38 Total $ 2,700 $ 1,300 $ 87 $ 60 $ 4,147 Liabilities: Energy-related derivatives (a) $ 426 $ 212 $ 11 $ — $ 649 Interest rate derivatives — 22 — — 22 Foreign currency derivatives — 90 — — 90 Contingent consideration — — 19 — 19 Total $ 426 $ 324 $ 30 $ — $ 780 Fair Value Measurements Using: As of March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Alabama Power Assets: Energy-related derivatives $ — $ 5 $ — $ — $ 5 Nuclear decommissioning trusts: (b) Domestic equity 368 99 — — 467 Foreign equity 52 50 — — 102 U.S. Treasury and government agency securities — 22 — — 22 Municipal bonds — 1 — — 1 Corporate bonds 23 141 — — 164 Mortgage and asset backed securities — 30 — — 30 Private equity — — — 60 60 Other 7 — — — 7 Cash equivalents 694 11 — — 705 Other investments — 29 — — 29 Total $ 1,144 $ 388 $ — $ 60 $ 1,592 Liabilities: Energy-related derivatives $ — $ 27 $ — $ — $ 27 Georgia Power Assets: Energy-related derivatives $ — $ 6 $ — $ — $ 6 Nuclear decommissioning trusts: (b)(c) Domestic equity 210 1 — — 211 Foreign equity — 119 — — 119 U.S. Treasury and government agency securities — 267 — — 267 Municipal bonds — 102 — — 102 Corporate bonds — 156 — — 156 Mortgage and asset backed securities — 56 — — 56 Other 16 5 — — 21 Cash equivalents 212 — — — 212 Total $ 438 $ 712 $ — $ — $ 1,150 Liabilities: Energy-related derivatives $ — $ 61 $ — $ — $ 61 Fair Value Measurements Using: As of March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Mississippi Power Assets: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Cash equivalents 79 — — — 79 Total $ 79 $ 3 $ — $ — $ 82 Liabilities: Energy-related derivatives $ — $ 33 $ — $ — $ 33 Southern Power Assets: Energy-related derivatives $ — $ 2 $ — $ — $ 2 Cash equivalents 166 — — — 166 Total $ 166 $ 2 $ — $ — $ 168 Liabilities: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Foreign currency derivatives — 90 — — 90 Contingent consideration — — 19 — 19 Total $ — $ 93 $ 19 $ — $ 112 Southern Company Gas Assets: Energy-related derivatives (a) $ 328 $ 148 $ 87 $ — $ 563 Non-qualified deferred compensation trusts: Domestic equity — 9 — — 9 Foreign equity — 3 — — 3 Pooled funds – fixed income — 16 — — 16 Cash equivalents and restricted cash 270 — — — 270 Total $ 598 $ 176 $ 87 $ — $ 861 Liabilities: Energy-related derivatives (a) $ 426 $ 88 $ 11 $ — $ 525 Interest rate derivatives — 21 — — 21 Total $ 426 $ 109 $ 11 $ — $ 546 (a) Energy-related derivatives exclude cash collateral of $128 million and $16 million associated with premiums and certain weather derivatives accounted for based on intrinsic value rather than fair value. (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 March 31, 2020 , approximately $31 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 months ended March 31, 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 March 31, 2020 Three Months Ended March 31, 2019 (in millions) Southern Company $ (247 ) $ 152 Alabama Power (167 ) 87 Georgia Power (80 ) 65 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 March 31, 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 $60 million and unfunded commitments related to the private equity investments totaled $73 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 March 31, 2020 , other financial instruments for which the carrying amount did not equal fair value were as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (*) (in millions) Long-term debt, including securities due within one year: Carrying amount $ 45,820 $ 8,432 $ 12,217 $ 1,413 $ 4,369 $ 5,836 Fair value 49,126 9,239 14,020 1,433 4,376 6,416 (*) 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 March 31, 2020 , the fair value of Southern Company Gas' Level 3 physical natural gas forward contracts was $76 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 March 31, 2020 (in millions) Beginning balance $ 14 Transfers to Level 3 70 Transfers from Level 3 (3 ) Instruments realized or otherwise settled during period (1 ) Changes in fair value (4 ) Ending balance $ 76 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 $(0.84) to $0.21 per mmBtu). Forward price increases (decreases) as of March 31, 2020 would have resulted in higher (lower) values on a net basis.

DERIVATIVES

DERIVATIVES	3 Months Ended
	Mar. 31, 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 March 31, 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 Purchased mmBtu Longest Hedge Date Longest Non-Hedge Date (in millions) Southern Company (*) 945 2023 2031 Alabama Power 88 2023 — Georgia Power 168 2023 — Mississippi Power 100 2023 — Southern Power 4 2020 2020 Southern Company Gas (*) 585 2022 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 4.0 billion mmBtu as of March 31, 2020 , which is also included in Southern Company's total volume. At March 31, 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 2020. 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 23 million mmBtu for Southern Company, which includes 6 million mmBtu for Alabama Power, 7 million mmBtu for Georgia Power, 3 million mmBtu for Mississippi Power, and 7 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 March 31, 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 March 31, 2020 , the following interest rate derivatives were outstanding: Notional Amount Interest Rate Received Weighted Average Interest Rate Paid Hedge Maturity Date Fair Value Gain (Loss) at March 31, 2020 (in millions) (in millions) Cash Flow Hedges of Forecasted Debt Southern Company Gas $ 200 3-month LIBOR 1.81% September 2030 $ (21 ) 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 300 2.75% 3-month LIBOR + 0.92% June 2020 1 Southern Company parent 1,500 2.35% 1-month LIBOR + 0.87% July 2021 21 Southern Company $ 2,060 $ 1 The estimated pre-tax gains (losses) related to interest rate derivatives expected to be reclassified from accumulated OCI to interest expense for the 12 -month period ending March 31, 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 March 31, 2020 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at March 31, 2020 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ (39 ) Southern Power 564 3.78% 500 1.85% June 2026 (51 ) Total $ 1,241 € 1,100 $ (90 ) 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 March 31, 2021 are $(24) 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 March 31, 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 $ 7 $ 100 $ 3 $ 70 Other deferred charges and assets/Other deferred credits and liabilities 8 40 6 44 Total derivatives designated as hedging instruments for regulatory purposes $ 15 $ 140 $ 9 $ 114 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 3 $ 6 $ 1 $ 6 Interest rate derivatives: Other current assets/Other current liabilities 12 21 2 23 Other deferred charges and assets/Other deferred credits and liabilities 10 — — 1 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 24 Other deferred charges and assets/Other deferred credits and liabilities — 66 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 25 $ 117 $ 19 $ 54 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 300 $ 297 $ 461 $ 358 Other deferred charges and assets/Other deferred credits and liabilities 261 206 207 225 Total derivatives not designated as hedging instruments $ 561 $ 503 $ 668 $ 583 Gross amounts recognized $ 601 $ 760 $ 696 $ 751 Gross amounts offset (a) (383 ) (511 ) (463 ) (562 ) Net amounts recognized in the Balance Sheets (b) $ 218 $ 249 $ 233 $ 189 As of March 31, 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 $ 3 $ 18 $ 2 $ 14 Other deferred charges and assets/Other deferred credits and liabilities 2 9 2 10 Total derivatives designated as hedging instruments for regulatory purposes $ 5 $ 27 $ 4 $ 24 Gross amounts recognized $ 5 $ 27 $ 4 $ 24 Gross amounts offset (4 ) (4 ) (2 ) (2 ) Net amounts recognized in the Balance Sheets $ 1 $ 23 $ 2 $ 22 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 3 $ 42 $ 1 $ 32 Other deferred charges and assets/Other deferred credits and liabilities 3 19 3 21 Total derivatives designated as hedging instruments for regulatory purposes $ 6 $ 61 $ 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 $ 6 $ 61 $ 4 $ 70 Gross amounts offset (6 ) (6 ) (3 ) (3 ) Net amounts recognized in the Balance Sheets $ — $ 55 $ 1 $ 67 As of March 31, 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 $ 1 $ 21 $ — $ 15 Other deferred charges and assets/Other deferred credits and liabilities 2 12 1 12 Total derivatives designated as hedging instruments for regulatory purposes $ 3 $ 33 $ 1 $ 27 Gross amounts recognized $ 3 $ 33 $ 1 $ 27 Gross amounts offset (3 ) (3 ) (1 ) (1 ) Net amounts recognized in the Balance Sheets $ — $ 30 $ — $ 26 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 2 $ 2 $ 1 $ 2 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 24 Other deferred charges and assets/Other deferred credits and liabilities — 66 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 2 $ 92 $ 17 $ 26 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ — $ 1 $ 2 $ 1 Total derivatives not designated as hedging instruments $ — $ 1 $ 2 $ 1 Gross amounts recognized $ 2 $ 93 $ 19 $ 27 Gross amounts offset — — — — Net amounts recognized in the Balance Sheets $ 2 $ 93 $ 19 $ 27 As of March 31, 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 $ — $ 19 $ — $ 9 Other deferred charges and assets/Other deferred credits and liabilities 1 — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 19 $ — $ 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 $ 1 $ 4 $ — $ 4 Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — 21 2 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 1 $ 25 $ 2 $ 4 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 300 $ 296 $ 459 $ 357 Other deferred charges and assets/Other deferred credits and liabilities 261 206 207 225 Total derivatives not designated as hedging instruments $ 561 $ 502 $ 666 $ 582 Gross amounts of recognized $ 563 $ 546 $ 668 $ 596 Gross amounts offset (a) (370 ) (498 ) (456 ) (555 ) Net amounts recognized in the Balance Sheets (b) $ 193 $ 48 $ 212 $ 41 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $128 million and $99 million as of March 31, 2020 and December 31, 2019 , respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $16 million and $4 million as of March 31, 2020 and December 31, 2019 , respectively. Energy-related derivatives not designated as hedging instruments were immaterial for the traditional electric operating companies at March 31, 2020 and December 31, 2019 . At March 31, 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 at March 31, 2020 Derivative Category and Balance Sheet Location Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Company Gas (*) (in millions) Energy-related derivatives: Other regulatory assets, current $ (79 ) $ (17 ) $ (39 ) $ (19 ) $ (4 ) Other regulatory assets, deferred (33 ) (7 ) (16 ) (10 ) — Other regulatory liabilities, current 5 1 — — 4 Total energy-related derivative gains (losses) $ (107 ) $ (23 ) $ (55 ) $ (29 ) $ — (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $19 million at March 31, 2020 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2019 Derivative Category and Balance Sheet Location Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Company Gas (*) (in millions) 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 (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $11 million at December 31, 2019. For the three months ended March 31, 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 March 31, 2020 2019 (in millions) Southern Company Energy-related derivatives $ (4 ) $ — Interest rate derivatives (26 ) — Foreign currency derivatives (83 ) (39 ) Total $ (113 ) $ (39 ) Southern Power Foreign currency derivatives $ (83 ) $ (39 ) Southern Company Gas Energy-related derivatives $ (4 ) $ — Interest rate derivatives (23 ) — Total $ (27 ) $ — For the three months ended March 31, 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 months ended March 31, 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 March 31, 2020 2019 (in millions) Southern Company Total cost of natural gas $ 439 $ 686 Gain (loss) on energy-related cash flow hedges (a) (7 ) 1 Total depreciation and amortization 857 751 Gain (loss) on energy-related cash flow hedges (a) (1 ) (3 ) Total interest expense, net of amounts capitalized (456 ) (430 ) Gain (loss) on interest rate cash flow hedges (a) (6 ) (5 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) Gain (loss) on interest rate fair value hedges (b) 29 14 Total other income (expense), net 103 78 Gain (loss) on foreign currency cash flow hedges (a)(c) (31 ) (24 ) Southern Power Total depreciation and amortization $ 117 $ 119 Gain (loss) on energy-related cash flow hedges (a) (1 ) (3 ) Total interest expense, net of amounts capitalized (39 ) (44 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) Total other income (expense), net 2 2 Gain (loss) on foreign currency cash flow hedges (a)(c) (31 ) (24 ) (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 months ended March 31, 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 March 31, 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 March 31, 2020 As of December 31, 2019 As of March 31, 2020 As of December 31, 2019 (in millions) (in millions) Southern Company Securities due within one year $ (600 ) $ (599 ) $ (1 ) $ — Long-term debt (1,519 ) (1,494 ) (22 ) 3 For the three months ended March 31, 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 March 31, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2020 2019 (in millions) Energy-related derivatives: Natural gas revenues (*) $ 70 $ 33 Cost of natural gas 7 8 Total derivatives in non-designated hedging relationships $ 77 $ 41 (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented. For the three months ended March 31, 2020 and 2019 , the pre-tax effects of energy-related derivatives and interest rate 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 March 31, 2020 , the Registrants had no collateral posted with derivative counterparties to satisfy these arrangements. For the Registrants with interest rate derivatives at March 31, 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 March 31, 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 March 31, 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 March 31, 2020 , cash collateral held on deposit in broker margin accounts was $128 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	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
ACQUISITIONS AND DISPOSITIONS	ACQUISITIONS AND DISPOSITIONS See 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. No Registrant had assets or liabilities held for sale at March 31, 2020 . Southern Power Acquisitions 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 fourth quarter 2020. 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 three months ended March 31, 2020 , Southern Power continued construction of the Reading and Skookumchuck wind facilities. Total aggregate construction costs, excluding acquisition costs, are expected to be between $490 million and $535 million for the two facilities under construction. At March 31, 2020 , total costs of construction incurred for these projects were $447 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 Under Construction as of March 31, 2020 Reading (a) Wind 200 Osage and Lyon Counties, KS May 2020 12 years Skookumchuck (b) Wind 136 Lewis and Thurston Counties, WA Second half of 2020 20 years (a) In 2018, Southern Power purchased 100% of the membership interests of the Reading facility pursuant to a joint development arrangement. Southern Power may enter into a tax equity partnership, in which case it would then own 100% of the Class B membership interests. The ultimate outcome of this matter cannot be determined at this time. (b) In October 2019, Southern Power purchased 100% of the membership interests of the Skookumchuck facility pursuant to a joint development arrangement. In December 2019, Southern Power entered into a tax equity agreement as the Class B member with funding of the tax equity amounts expected to occur upon commercial operation. Shortly after com m ercial operation, Southern Power may sell a noncontrolling interest in these Class B membership interests to another partner. 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 three months ended March 31, 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 March 31, 2020 and 2019 is presented below: Three Months Ended March 31, 2020 2019 (in millions) Southern Power's earnings before income taxes: (*) Plant Nacogdoches N/A $ 6 Plant Mankato $ 2 $ 1 (*) 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 estimated working capital adjustments. The preliminary loss associated with the transactions was immaterial. Southern Company Gas may also receive two future payments of $5 million each, contingent upon certain milestones related to Pivotal LNG being met by Dominion Modular LNG Holdings, Inc. 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	3 Months Ended
	Mar. 31, 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. Southern Company's reportable business segments are the sale of electricity by the traditional electric operating companies, the sale of electricity in the competitive wholesale market by Southern Power, and the sale of natural gas and other complementary products and services by Southern Company Gas. Revenues from sales by Southern Power to the traditional electric operating companies were $86 million for the three months ended March 31, 2020 and $87 million for the three months ended March 31, 2019 . Revenues from sales of natural gas from Southern Company Gas to the traditional electric operating companies were immaterial for the three months ended March 31, 2020 and 2019. Revenues from sales of natural gas from Southern Company Gas to Southern Power were $10 million for the three months ended March 31, 2020 and $17 million for the three months ended March 31, 2019 . The "All Other" column includes the Southern Company parent entity, which does not allocate operating expenses to business segments. Also, this category includes segments below the quantitative threshold for separate disclosure. These segments include providing energy solutions to electric utilities and their customers in the areas of distributed generation, energy storage and renewables, and energy efficiency, as well as investments in telecommunications and leveraged lease projects. All other inter-segment revenues are not material. Financial data for business segments and products and services for the three months ended March 31, 2020 and 2019 was as follows: Electric Utilities Traditional Electric Operating Companies Southern Power Eliminations Total Southern Company Gas All Other Eliminations Consolidated (in millions) Three Months Ended March 31, 2020 Operating revenues $ 3,407 $ 375 $ (87 ) $ 3,695 $ 1,249 $ 114 $ (40 ) $ 5,018 Segment net income (loss) (a)(b) 642 75 — 717 275 (121 ) (3 ) 868 At March 31, 2020 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 81,765 13,646 (695 ) 94,716 21,617 3,467 (948 ) 118,852 Three Months Ended March 31, 2019 Operating revenues $ 3,445 $ 443 $ (93 ) $ 3,795 $ 1,474 $ 182 $ (39 ) $ 5,412 Segment net income (loss) (a)(c) 565 56 — 621 270 1,195 (2 ) 2,084 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 Southern Power includes a $39 million pre-tax gain ( $23 million gain after tax) on the sale of Plant Mankato for the three months ended March 31, 2020 . See Note (K) under " Southern Power " for additional information. (c) 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 three months ended March 31, 2019. See Note 15 to the financial statements in Item 8 of the Form 10-K under " Southern Company" for additional information. Products and Services Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended March 31, 2020 $ 3,078 $ 418 $ 199 $ 3,695 Three Months Ended March 31, 2019 3,084 499 212 3,795 Southern Company Gas' Revenues Gas Wholesale Gas Services (*) Gas Other Total (in millions) Three Months Ended March 31, 2020 $ 1,013 $ 51 $ 177 $ 8 $ 1,249 Three Months Ended March 31, 2019 1,161 86 229 (2 ) 1,474 (*) 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 and Illinois through SouthStar Energy Services, LLC. 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 months ended March 31, 2020 and 2019 was as follows: Gas Distribution Operations Gas Pipeline Investments Wholesale Gas Services (*) Gas Marketing Services Total All Other Eliminations Consolidated (in millions) Three Months Ended March 31, 2020 Operating revenues $ 1,020 $ 8 $ 51 $ 177 $ 1,256 $ 8 $ (15 ) $ 1,249 Segment net income (loss) 164 30 23 57 274 1 — 275 Total assets at March 31, 2020 18,166 1,652 643 1,517 21,978 11,094 (11,455 ) 21,617 Three Months Ended March 31, 2019 Operating revenues $ 1,172 $ 8 $ 86 $ 229 $ 1,495 $ 11 $ (32 ) $ 1,474 Segment net income (loss) 133 32 47 61 273 (3 ) — 270 Total assets at December 31, 2019 18,204 1,678 850 1,496 22,228 10,759 (11,300 ) 21,687 (*) 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 March 31, 2020 $ 1,185 $ 29 $ 1,214 $ 1,163 $ 51 Three Months Ended March 31, 2019 1,926 88 2,014 1,928 86

INTRODUCTION (Policies)

INTRODUCTION (Policies)	3 Months Ended
	Mar. 31, 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 March 31, 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, 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 could continue to disrupt supply chains and capital markets, 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. Southern Company Gas had no material adjustments for any period presented.
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)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Goodwill	Goodwill at March 31, 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 March 31, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Intangible Assets, Net Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (121 ) $ 91 $ 212 $ (116 ) $ 96 Trade names 64 (26 ) 38 64 (25 ) 39 Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 PPA fair value adjustments 390 (74 ) 316 390 (69 ) 321 Other 10 (8 ) 2 11 (8 ) 3 Total other intangible assets subject to amortization $ 740 $ (292 ) $ 448 $ 741 $ (280 ) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (292 ) $ 523 $ 816 $ (280 ) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (74 ) $ 316 $ 390 $ (69 ) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (108 ) $ 48 $ 156 $ (104 ) $ 52 Trade names 26 (10 ) 16 26 (10 ) 16 Wholesale gas services Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 Total other intangible assets subject to amortization $ 246 $ (181 ) $ 65 $ 246 $ (176 ) $ 70
Schedule of Other Intangible Assets, Finite-Lived	Other intangible assets were as follows: At March 31, 2020 At December 31, 2019 Gross Carrying Amount Accumulated Amortization Other Intangible Assets, Net Gross Carrying Amount Accumulated Amortization Other (in millions) (in millions) Southern Company Other intangible assets subject to amortization: Customer relationships $ 212 $ (121 ) $ 91 $ 212 $ (116 ) $ 96 Trade names 64 (26 ) 38 64 (25 ) 39 Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 PPA fair value adjustments 390 (74 ) 316 390 (69 ) 321 Other 10 (8 ) 2 11 (8 ) 3 Total other intangible assets subject to amortization $ 740 $ (292 ) $ 448 $ 741 $ (280 ) $ 461 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (292 ) $ 523 $ 816 $ (280 ) $ 536 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 390 $ (74 ) $ 316 $ 390 $ (69 ) $ 321 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (108 ) $ 48 $ 156 $ (104 ) $ 52 Trade names 26 (10 ) 16 26 (10 ) 16 Wholesale gas services Storage and transportation contracts 64 (63 ) 1 64 (62 ) 2 Total other intangible assets subject to amortization $ 246 $ (181 ) $ 65 $ 246 $ (176 ) $ 70
Finite-lived Intangible Assets Amortization Expense	Amortization associated with other intangible assets was as follows: Three Months Ended March 31, 2020 (in millions) Southern Company (a) $ 12 Southern Power (b) $ 5 Southern Company Gas Gas marketing services $ 4 Wholesale gas services (b) 1 Southern Company Gas total $ 5 (a) Includes $6 million for the three months ended March 31, 2020 , 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 March 31, 2020 and/or December 31, 2019 : Southern Company Southern Company Gas At March 31, 2020 At December 31, 2019 At March 31, 2020 At December 31, 2019 (in millions) (in millions) Cash and cash equivalents $ 2,164 $ 1,975 $ 311 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — 3 Other current assets 3 — 3 — Total cash, cash equivalents, and restricted cash $ 2,168 (b) $ 1,978 $ 314 $ 49 (a) Represents restricted cash held by Southern Company Gas as collateral for workers' compensation, life insurance, and long-term disability insurance. (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 March 31, 2020 and/or December 31, 2019 : Southern Company Southern Company Gas At March 31, 2020 At December 31, 2019 At March 31, 2020 At December 31, 2019 (in millions) (in millions) Cash and cash equivalents $ 2,164 $ 1,975 $ 311 $ 46 Restricted cash (a) : Other accounts and notes receivable — 3 — 3 Other current assets 3 — 3 — Total cash, cash equivalents, and restricted cash $ 2,168 (b) $ 1,978 $ 314 $ 49 (a) Represents restricted cash held by Southern Company Gas as collateral for workers' compensation, life insurance, and long-term disability insurance. (b) Total does not add due to rounding.

REGULATORY MATTERS (Tables)

REGULATORY MATTERS (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2020 and December 31, 2019 were as follows: Regulatory Clause Balance Sheet Line Item March 31, December 31, (in millions) Alabama Power Rate CNP Compliance Other regulatory liabilities, current $ 35 $ 55 Other regulatory liabilities, deferred 17 7 Rate CNP PPA Deferred under recovered regulatory clause revenues 37 40 Retail Energy Cost Recovery Other regulatory liabilities, current 74 32 Other regulatory liabilities, deferred 22 17 Natural Disaster Reserve Other regulatory liabilities, current 27 37 Other regulatory liabilities, deferred 104 113 Georgia Power Fuel Cost Recovery Other current liabilities $ 6 $ — Other deferred credits and liabilities 163 73 Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 25 $ 23 Ad Valorem Tax Other regulatory assets 11 47 Other regulatory assets, deferred 38 — Property Damage Reserve Other regulatory liabilities, deferred 53 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) $ 8.2 Construction contingency estimate 0.2 Total project capital cost forecast (a)(b) 8.4 Net investment as of March 31, 2020 (b) (6.2 ) Remaining estimate to complete (a) $ 2.2 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $270 million , of which $36 million had been accrued through March 31, 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)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables disaggregate revenue from contracts with customers for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating revenues Retail electric revenues Residential $ 1,370 $ 553 $ 760 $ 57 $ — $ — Commercial 1,146 364 720 62 — — Industrial 680 321 281 78 — — Other 23 5 16 2 — — Total retail electric revenues 3,219 1,243 1,777 199 — — Natural gas distribution revenues Residential 496 — — — — 496 Commercial 130 — — — — 130 Transportation 264 — — — — 264 Industrial 12 — — — — 12 Other 97 — — — — 97 Total natural gas distribution revenues 999 — — — — 999 Wholesale electric revenues PPA energy revenues 159 27 9 2 125 — PPA capacity revenues 105 27 12 1 66 — Non-PPA revenues 51 19 2 69 58 — Total wholesale electric revenues 315 73 23 72 249 — Other natural gas revenues Wholesale gas services 396 — — — — 396 Gas marketing services 163 — — — — 163 Other natural gas revenues 7 — — — — 7 Total natural gas revenues 566 — — — — 566 Other revenues 192 37 95 5 3 — Total revenue from contracts with customers 5,291 1,353 1,895 276 252 1,565 Other revenue sources (a) 868 (2 ) (70 ) 1 123 825 Other adjustments (b) (1,141 ) — — — — (1,141 ) Total operating revenues $ 5,018 $ 1,351 $ 1,825 $ 277 $ 375 $ 1,249 (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. Three Months Ended March 31, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating revenues Retail electric revenues Residential $ 1,327 $ 559 $ 708 $ 60 $ — $ — Commercial 1,125 368 692 65 — — Industrial 708 338 296 74 — — Other 21 6 11 4 — — Total retail electric revenues 3,181 1,271 1,707 203 — — Natural gas distribution revenues Residential 601 — — — — 601 Commercial 170 — — — — 170 Transportation 256 — — — — 256 Industrial 17 — — — — 17 Other 116 — — — — 116 Total natural gas distribution revenues 1,160 — — — — 1,160 Wholesale electric revenues PPA energy revenues 190 31 12 3 151 — PPA capacity revenues 107 27 13 1 81 — Non-PPA revenues 55 60 2 74 41 — Total wholesale electric revenues 352 118 27 78 273 — Other natural gas revenues Wholesale gas services 721 — — — — 721 Gas marketing services 221 — — — — 221 Other natural gas revenues 10 — — — — 10 Total natural gas revenues 952 — — — — 952 Other revenues 266 46 92 5 4 — Total revenue from contracts with customers 5,911 1,435 1,826 286 277 2,112 Other revenue sources (a) 1,361 (27 ) 7 1 166 1,222 Other adjustments (b) (1,860 ) — — — — (1,860 ) Total operating revenues $ 5,412 $ 1,408 $ 1,833 $ 287 $ 443 $ 1,474 (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 March 31, 2020 and December 31, 2019 : Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Accounts Receivables As of March 31, 2020 $ 2,224 $ 518 $ 697 $ 70 $ 86 $ 696 As of December 31, 2019 2,413 586 688 79 97 749 Contract Assets As of March 31, 2020 $ 100 $ — $ 53 $ 3 $ — $ — As of December 31, 2019 117 — 69 — — — Contract Liabilities As of March 31, 2020 $ 49 $ 7 $ 11 $ — $ 1 $ 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 March 31, 2020 are expected to be recognized as follows: 2020 (remaining) 2021 2022 2023 2024 2025 and Thereafter (in millions) Southern Company $ 367 $ 416 $ 354 $ 334 $ 314 $ 2,164 Alabama Power 23 33 31 24 7 5 Georgia Power 52 66 36 34 23 61 Southern Power 224 285 287 277 285 2,116
Summary of Lease Income	Lease income for the three months ended March 31, 2020 and 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended March 31, 2020 Lease income - interest income on sales-type leases $ 3 $ — $ — $ 3 $ — $ — Lease income - operating leases 51 6 16 — 24 9 Variable lease income 74 — — — 80 — Total lease income $ 128 $ 6 $ 16 $ 3 $ 104 $ 9 For the Three Months Ended March 31, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 71 7 19 — 46 9 Variable lease income 66 — — — 75 — Total lease income $ 139 $ 7 $ 19 $ 2 $ 121 $ 9

CONSOLIDATED ENTITIES AND EQU_2

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
Regulated Operations [Abstract]
Equity Method Investments	Selected financial information of SNG for the three months ended March 31, 2020 and 2019 is as follows: Income Statement Information Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 (in millions) Revenues $ 158 $ 166 Operating income 98 106 Net income 75 84 The carrying amounts of Southern Company Gas' equity method investments as of March 31, 2020 and December 31, 2019 and related income from those investments for the three -month periods ended March 31, 2020 and 2019 were as follows: Investment Balance March 31, 2020 December 31, 2019 (a) (in millions) SNG (b) $ 1,216 $ 1,137 PennEast Pipeline (c) 85 82 Other 32 32 Total $ 1,333 $ 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.
Schedule of Other Nonoperating Income, by Component	Earnings from Equity Method Investments Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 (in millions) SNG $ 37 $ 42 Atlantic Coast Pipeline (*) 3 3 PennEast Pipeline (*) 2 2 Other 1 1 Total $ 43 $ 48

FINANCING (Tables)

FINANCING (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Credit Arrangements by Company	At March 31, 2020 , committed credit arrangements with banks were as follows: Expires Company 2020 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 1,733 — Mississippi Power — 150 125 — 275 210 — 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 $ 7,636 $ 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 $25 million and $60 million , respectively, was unused at March 31, 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 March 31, 2020 Three Months Ended March 31, 2019 (in millions) As reported shares 1,057 1,038 Effect of stock-based compensation 7 7 Effect of equity units 3 — Diluted shares 1,067 1,045

RETIREMENT BENEFITS (Tables)

RETIREMENT BENEFITS (Tables)	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Pension Plans and Postretirement Plans	Components of the net periodic benefit costs for the three months ended March 31, 2020 and 2019 are presented in the following tables. Three Months Ended March 31, 2020 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 94 $ 22 $ 24 $ 4 $ 2 $ 8 Interest cost 108 25 33 5 1 8 Expected return on plan assets (275 ) (66 ) (87 ) (13 ) (3 ) (19 ) Amortization: Prior service costs 1 — — — — (1 ) Regulatory asset — — — — — 4 Net (gain)/loss 67 18 22 3 1 2 Net periodic pension cost (income) $ (5 ) $ (1 ) $ (8 ) $ (1 ) $ 1 $ 2 Postretirement Benefits Service cost $ 5 $ 2 $ 1 $ — $ — $ — Interest cost 13 3 5 — — 2 Expected return on plan assets (18 ) (7 ) (7 ) — — (2 ) Amortization: Regulatory asset — — — — — 2 Net (gain)/loss 1 — 1 — — (1 ) Net periodic postretirement benefit cost $ 1 $ (2 ) $ — $ — $ — $ 1 Three Months Ended March 31, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 73 $ 17 $ 19 $ 3 $ 2 $ 6 Interest cost 123 28 39 6 1 9 Expected return on plan assets (221 ) (51 ) (73 ) (10 ) (2 ) (15 ) Amortization: Prior service costs — — — — — (1 ) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (4 ) $ — $ 1 $ 3 Postretirement Benefits Service cost $ 5 $ 1 $ 1 $ — $ — $ 1 Interest cost 17 4 7 1 — 2 Expected return on plan assets (16 ) (6 ) (6 ) — — (2 ) Amortization: Prior service costs 1 1 — — — — Regulatory asset — — — — — 2 Net (gain)/loss (1 ) — — — — (1 ) Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	As of March 31, 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 March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Southern Company Assets: Energy-related derivatives (a) $ 328 $ 164 $ 87 $ — $ 579 Interest rate derivatives — 22 — — 22 Investments in trusts: (b)(c) Domestic equity 578 108 — — 686 Foreign equity 52 171 — — 223 U.S. Treasury and government agency securities — 289 — — 289 Municipal bonds — 103 — — 103 Pooled funds – fixed income — 16 — — 16 Corporate bonds 23 297 — — 320 Mortgage and asset backed securities — 85 — — 85 Private equity — — — 60 60 Other 24 5 — — 29 Cash equivalents 1,686 11 — — 1,697 Other investments 9 29 — — 38 Total $ 2,700 $ 1,300 $ 87 $ 60 $ 4,147 Liabilities: Energy-related derivatives (a) $ 426 $ 212 $ 11 $ — $ 649 Interest rate derivatives — 22 — — 22 Foreign currency derivatives — 90 — — 90 Contingent consideration — — 19 — 19 Total $ 426 $ 324 $ 30 $ — $ 780 Fair Value Measurements Using: As of March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Alabama Power Assets: Energy-related derivatives $ — $ 5 $ — $ — $ 5 Nuclear decommissioning trusts: (b) Domestic equity 368 99 — — 467 Foreign equity 52 50 — — 102 U.S. Treasury and government agency securities — 22 — — 22 Municipal bonds — 1 — — 1 Corporate bonds 23 141 — — 164 Mortgage and asset backed securities — 30 — — 30 Private equity — — — 60 60 Other 7 — — — 7 Cash equivalents 694 11 — — 705 Other investments — 29 — — 29 Total $ 1,144 $ 388 $ — $ 60 $ 1,592 Liabilities: Energy-related derivatives $ — $ 27 $ — $ — $ 27 Georgia Power Assets: Energy-related derivatives $ — $ 6 $ — $ — $ 6 Nuclear decommissioning trusts: (b)(c) Domestic equity 210 1 — — 211 Foreign equity — 119 — — 119 U.S. Treasury and government agency securities — 267 — — 267 Municipal bonds — 102 — — 102 Corporate bonds — 156 — — 156 Mortgage and asset backed securities — 56 — — 56 Other 16 5 — — 21 Cash equivalents 212 — — — 212 Total $ 438 $ 712 $ — $ — $ 1,150 Liabilities: Energy-related derivatives $ — $ 61 $ — $ — $ 61 Fair Value Measurements Using: As of March 31, 2020: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Net Asset Value as a Practical Expedient (NAV) Total (in millions) Mississippi Power Assets: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Cash equivalents 79 — — — 79 Total $ 79 $ 3 $ — $ — $ 82 Liabilities: Energy-related derivatives $ — $ 33 $ — $ — $ 33 Southern Power Assets: Energy-related derivatives $ — $ 2 $ — $ — $ 2 Cash equivalents 166 — — — 166 Total $ 166 $ 2 $ — $ — $ 168 Liabilities: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Foreign currency derivatives — 90 — — 90 Contingent consideration — — 19 — 19 Total $ — $ 93 $ 19 $ — $ 112 Southern Company Gas Assets: Energy-related derivatives (a) $ 328 $ 148 $ 87 $ — $ 563 Non-qualified deferred compensation trusts: Domestic equity — 9 — — 9 Foreign equity — 3 — — 3 Pooled funds – fixed income — 16 — — 16 Cash equivalents and restricted cash 270 — — — 270 Total $ 598 $ 176 $ 87 $ — $ 861 Liabilities: Energy-related derivatives (a) $ 426 $ 88 $ 11 $ — $ 525 Interest rate derivatives — 21 — — 21 Total $ 426 $ 109 $ 11 $ — $ 546 (a) Energy-related derivatives exclude cash collateral of $128 million and $16 million associated with premiums and certain weather derivatives accounted for based on intrinsic value rather than fair value. (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 March 31, 2020 , approximately $31 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 months ended March 31, 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 March 31, 2020 Three Months Ended March 31, 2019 (in millions) Southern Company $ (247 ) $ 152 Alabama Power (167 ) 87 Georgia Power (80 ) 65
Financial Instruments for Which Carrying Amount Did Not Equal Fair Value	As of March 31, 2020 , other financial instruments for which the carrying amount did not equal fair value were as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (*) (in millions) Long-term debt, including securities due within one year: Carrying amount $ 45,820 $ 8,432 $ 12,217 $ 1,413 $ 4,369 $ 5,836 Fair value 49,126 9,239 14,020 1,433 4,376 6,416 (*) 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 March 31, 2020 (in millions) Beginning balance $ 14 Transfers to Level 3 70 Transfers from Level 3 (3 ) Instruments realized or otherwise settled during period (1 ) Changes in fair value (4 ) Ending balance $ 76

DERIVATIVES (Tables)

DERIVATIVES (Tables)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Energy-Related Derivatives	At March 31, 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 Purchased mmBtu Longest Hedge Date Longest Non-Hedge Date (in millions) Southern Company (*) 945 2023 2031 Alabama Power 88 2023 — Georgia Power 168 2023 — Mississippi Power 100 2023 — Southern Power 4 2020 2020 Southern Company Gas (*) 585 2022 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 4.0 billion mmBtu as of March 31, 2020 , which is also included in Southern Company's total volume.
Schedule of Interest Rate Derivatives	At March 31, 2020 , the following interest rate derivatives were outstanding: Notional Amount Interest Rate Received Weighted Average Interest Rate Paid Hedge Maturity Date Fair Value Gain (Loss) at March 31, 2020 (in millions) (in millions) Cash Flow Hedges of Forecasted Debt Southern Company Gas $ 200 3-month LIBOR 1.81% September 2030 $ (21 ) 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 300 2.75% 3-month LIBOR + 0.92% June 2020 1 Southern Company parent 1,500 2.35% 1-month LIBOR + 0.87% July 2021 21 Southern Company $ 2,060 $ 1
Schedule of Foreign Currency Derivatives	At March 31, 2020 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at March 31, 2020 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ (39 ) Southern Power 564 3.78% 500 1.85% June 2026 (51 ) Total $ 1,241 € 1,100 $ (90 )
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 March 31, 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 $ 7 $ 100 $ 3 $ 70 Other deferred charges and assets/Other deferred credits and liabilities 8 40 6 44 Total derivatives designated as hedging instruments for regulatory purposes $ 15 $ 140 $ 9 $ 114 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 3 $ 6 $ 1 $ 6 Interest rate derivatives: Other current assets/Other current liabilities 12 21 2 23 Other deferred charges and assets/Other deferred credits and liabilities 10 — — 1 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 24 Other deferred charges and assets/Other deferred credits and liabilities — 66 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 25 $ 117 $ 19 $ 54 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 300 $ 297 $ 461 $ 358 Other deferred charges and assets/Other deferred credits and liabilities 261 206 207 225 Total derivatives not designated as hedging instruments $ 561 $ 503 $ 668 $ 583 Gross amounts recognized $ 601 $ 760 $ 696 $ 751 Gross amounts offset (a) (383 ) (511 ) (463 ) (562 ) Net amounts recognized in the Balance Sheets (b) $ 218 $ 249 $ 233 $ 189 As of March 31, 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 $ 3 $ 18 $ 2 $ 14 Other deferred charges and assets/Other deferred credits and liabilities 2 9 2 10 Total derivatives designated as hedging instruments for regulatory purposes $ 5 $ 27 $ 4 $ 24 Gross amounts recognized $ 5 $ 27 $ 4 $ 24 Gross amounts offset (4 ) (4 ) (2 ) (2 ) Net amounts recognized in the Balance Sheets $ 1 $ 23 $ 2 $ 22 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 3 $ 42 $ 1 $ 32 Other deferred charges and assets/Other deferred credits and liabilities 3 19 3 21 Total derivatives designated as hedging instruments for regulatory purposes $ 6 $ 61 $ 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 $ 6 $ 61 $ 4 $ 70 Gross amounts offset (6 ) (6 ) (3 ) (3 ) Net amounts recognized in the Balance Sheets $ — $ 55 $ 1 $ 67 As of March 31, 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 $ 1 $ 21 $ — $ 15 Other deferred charges and assets/Other deferred credits and liabilities 2 12 1 12 Total derivatives designated as hedging instruments for regulatory purposes $ 3 $ 33 $ 1 $ 27 Gross amounts recognized $ 3 $ 33 $ 1 $ 27 Gross amounts offset (3 ) (3 ) (1 ) (1 ) Net amounts recognized in the Balance Sheets $ — $ 30 $ — $ 26 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 2 $ 2 $ 1 $ 2 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 24 Other deferred charges and assets/Other deferred credits and liabilities — 66 16 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 2 $ 92 $ 17 $ 26 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ — $ 1 $ 2 $ 1 Total derivatives not designated as hedging instruments $ — $ 1 $ 2 $ 1 Gross amounts recognized $ 2 $ 93 $ 19 $ 27 Gross amounts offset — — — — Net amounts recognized in the Balance Sheets $ 2 $ 93 $ 19 $ 27 As of March 31, 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 $ — $ 19 $ — $ 9 Other deferred charges and assets/Other deferred credits and liabilities 1 — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 19 $ — $ 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 $ 1 $ 4 $ — $ 4 Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — 21 2 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 1 $ 25 $ 2 $ 4 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 300 $ 296 $ 459 $ 357 Other deferred charges and assets/Other deferred credits and liabilities 261 206 207 225 Total derivatives not designated as hedging instruments $ 561 $ 502 $ 666 $ 582 Gross amounts of recognized $ 563 $ 546 $ 668 $ 596 Gross amounts offset (a) (370 ) (498 ) (456 ) (555 ) Net amounts recognized in the Balance Sheets (b) $ 193 $ 48 $ 212 $ 41 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $128 million and $99 million as of March 31, 2020 and December 31, 2019 , respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $16 million and $4 million as of March 31, 2020 and December 31, 2019 , respectively.
Pre-tax Effects of Unrealized Derivative Gains (Losses) Arising from Energy-Related Derivative Instruments	At March 31, 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 at March 31, 2020 Derivative Category and Balance Sheet Location Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Company Gas (*) (in millions) Energy-related derivatives: Other regulatory assets, current $ (79 ) $ (17 ) $ (39 ) $ (19 ) $ (4 ) Other regulatory assets, deferred (33 ) (7 ) (16 ) (10 ) — Other regulatory liabilities, current 5 1 — — 4 Total energy-related derivative gains (losses) $ (107 ) $ (23 ) $ (55 ) $ (29 ) $ — (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $19 million at March 31, 2020 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2019 Derivative Category and Balance Sheet Location Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Company Gas (*) (in millions) 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 (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $11 million at December 31, 2019.
Pre-tax Effects of Interest Rate Derivatives, Designated as Cash Flow Hedging Instruments	For the three months ended March 31, 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 March 31, 2020 2019 (in millions) Southern Company Energy-related derivatives $ (4 ) $ — Interest rate derivatives (26 ) — Foreign currency derivatives (83 ) (39 ) Total $ (113 ) $ (39 ) Southern Power Foreign currency derivatives $ (83 ) $ (39 ) Southern Company Gas Energy-related derivatives $ (4 ) $ — Interest rate derivatives (23 ) — Total $ (27 ) $ —
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location	For the three months ended March 31, 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 March 31, 2020 2019 (in millions) Southern Company Total cost of natural gas $ 439 $ 686 Gain (loss) on energy-related cash flow hedges (a) (7 ) 1 Total depreciation and amortization 857 751 Gain (loss) on energy-related cash flow hedges (a) (1 ) (3 ) Total interest expense, net of amounts capitalized (456 ) (430 ) Gain (loss) on interest rate cash flow hedges (a) (6 ) (5 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) Gain (loss) on interest rate fair value hedges (b) 29 14 Total other income (expense), net 103 78 Gain (loss) on foreign currency cash flow hedges (a)(c) (31 ) (24 ) Southern Power Total depreciation and amortization $ 117 $ 119 Gain (loss) on energy-related cash flow hedges (a) (1 ) (3 ) Total interest expense, net of amounts capitalized (39 ) (44 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) Total other income (expense), net 2 2 Gain (loss) on foreign currency cash flow hedges (a)(c) (31 ) (24 ) (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 March 31, 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 March 31, 2020 As of December 31, 2019 As of March 31, 2020 As of December 31, 2019 (in millions) (in millions) Southern Company Securities due within one year $ (600 ) $ (599 ) $ (1 ) $ — Long-term debt (1,519 ) (1,494 ) (22 ) 3
Pre-tax Effect of Interest Rate and Energy Related Derivatives	For the three months ended March 31, 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 March 31, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2020 2019 (in millions) Energy-related derivatives: Natural gas revenues (*) $ 70 $ 33 Cost of natural gas 7 8 Total derivatives in non-designated hedging relationships $ 77 $ 41 (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented.

ACQUISITIONS AND DISPOSITIONS (

ACQUISITIONS AND DISPOSITIONS (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Schedule of Construction Projects	Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Under Construction as of March 31, 2020 Reading (a) Wind 200 Osage and Lyon Counties, KS May 2020 12 years Skookumchuck (b) Wind 136 Lewis and Thurston Counties, WA Second half of 2020 20 years (a) In 2018, Southern Power purchased 100% of the membership interests of the Reading facility pursuant to a joint development arrangement. Southern Power may enter into a tax equity partnership, in which case it would then own 100% of the Class B membership interests. 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 March 31, 2020 and 2019 is presented below: Three Months Ended March 31, 2020 2019 (in millions) Southern Power's earnings before income taxes: (*) Plant Nacogdoches N/A $ 6 Plant Mankato $ 2 $ 1 (*) 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)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Financial Data for Business Segments	Financial data for business segments and products and services for the three months ended March 31, 2020 and 2019 was as follows: Electric Utilities Traditional Electric Operating Companies Southern Power Eliminations Total Southern Company Gas All Other Eliminations Consolidated (in millions) Three Months Ended March 31, 2020 Operating revenues $ 3,407 $ 375 $ (87 ) $ 3,695 $ 1,249 $ 114 $ (40 ) $ 5,018 Segment net income (loss) (a)(b) 642 75 — 717 275 (121 ) (3 ) 868 At March 31, 2020 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 81,765 13,646 (695 ) 94,716 21,617 3,467 (948 ) 118,852 Three Months Ended March 31, 2019 Operating revenues $ 3,445 $ 443 $ (93 ) $ 3,795 $ 1,474 $ 182 $ (39 ) $ 5,412 Segment net income (loss) (a)(c) 565 56 — 621 270 1,195 (2 ) 2,084 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 Southern Power includes a $39 million pre-tax gain ( $23 million gain after tax) on the sale of Plant Mankato for the three months ended March 31, 2020 . See Note (K) under " Southern Power " for additional information. (c) 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 three months ended March 31, 2019. See Note 15 to the financial statements in Item 8 of the Form 10-K under " Southern Company" for additional information. Business segment financial data for the three months ended March 31, 2020 and 2019 was as follows: Gas Distribution Operations Gas Pipeline Investments Wholesale Gas Services (*) Gas Marketing Services Total All Other Eliminations Consolidated (in millions) Three Months Ended March 31, 2020 Operating revenues $ 1,020 $ 8 $ 51 $ 177 $ 1,256 $ 8 $ (15 ) $ 1,249 Segment net income (loss) 164 30 23 57 274 1 — 275 Total assets at March 31, 2020 18,166 1,652 643 1,517 21,978 11,094 (11,455 ) 21,617 Three Months Ended March 31, 2019 Operating revenues $ 1,172 $ 8 $ 86 $ 229 $ 1,495 $ 11 $ (32 ) $ 1,474 Segment net income (loss) 133 32 47 61 273 (3 ) — 270 Total assets at December 31, 2019 18,204 1,678 850 1,496 22,228 10,759 (11,300 ) 21,687 (*) 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 March 31, 2020 $ 1,185 $ 29 $ 1,214 $ 1,163 $ 51 Three Months Ended March 31, 2019 1,926 88 2,014 1,928 86
Financial Data for Products and Services	Products and Services Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended March 31, 2020 $ 3,078 $ 418 $ 199 $ 3,695 Three Months Ended March 31, 2019 3,084 499 212 3,795 Southern Company Gas' Revenues Gas Wholesale Gas Services (*) Gas Other Total (in millions) Three Months Ended March 31, 2020 $ 1,013 $ 51 $ 177 $ 8 $ 1,249 Three Months Ended March 31, 2019 1,161 86 229 (2 ) 1,474 (*) 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) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		$ 5,280,000,000		$ 5,280,000,000
SOUTHERN Co GAS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		5,015,000,000		$ 5,015,000,000
Inventory decrement		0	$ 0
PowerSecure
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill		$ 263,000,000
Maximum | Natural Gas Generating Facility | SOUTHERN POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, Plant and Equipment, Useful Life	50 years			45 years

INTRODUCTION - Goodwill (Detail

INTRODUCTION - Goodwill (Details) - USD ($) $ in Millions	Mar. 31, 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
SOUTHERN Co GAS | Gas Marketing Services
Goodwill [Line Items]
Goodwill	$ 981

INTRODUCTION - Other Intangible

INTRODUCTION - Other Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Other intangible assets subject to amortization:
Gross Carrying Amount	$ 740	$ 741
Accumulated Amortization	(292)	(280)
Other Intangible Assets, Net	448	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	(292)	(280)
Other Intangible Assets, Net	523	536
Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	212	212
Accumulated Amortization	(121)	(116)
Other Intangible Assets, Net	91	96
Total other intangible assets
Accumulated Amortization	(121)	(116)
Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(26)	(25)
Other Intangible Assets, Net	38	39
Total other intangible assets
Accumulated Amortization	(26)	(25)
Storage and transportation contracts
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(63)	(62)
Other Intangible Assets, Net	1	2
Total other intangible assets
Accumulated Amortization	(63)	(62)
PPA fair value adjustments
Other intangible assets subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(74)	(69)
Other Intangible Assets, Net	316	321
Total other intangible assets
Accumulated Amortization	(74)	(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	(74)	(69)
Total other intangible assets
Accumulated Amortization	(74)	(69)
SOUTHERN POWER CO | PPA fair value adjustments
Other intangible assets subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(74)	(69)
Other Intangible Assets, Net	316	321
Total other intangible assets
Accumulated Amortization	(74)	(69)
SOUTHERN Co GAS
Other intangible assets subject to amortization:
Gross Carrying Amount	246	246
Accumulated Amortization	(181)	(176)
Other Intangible Assets, Net	65	70
Total other intangible assets
Accumulated Amortization	(181)	(176)
Other Intangible Assets, Net	65	70
SOUTHERN Co GAS | Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	156	156
Accumulated Amortization	(108)	(104)
Other Intangible Assets, Net	48	52
Total other intangible assets
Accumulated Amortization	(108)	(104)
SOUTHERN Co GAS | Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	26	26
Accumulated Amortization	(10)	(10)
Other Intangible Assets, Net	16	16
Total other intangible assets
Accumulated Amortization	(10)	(10)
SOUTHERN Co GAS | Storage and transportation contracts
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(63)	(62)
Other Intangible Assets, Net	1	2
Total other intangible assets
Accumulated Amortization	$ (63)	$ (62)

INTRODUCTION - Intangibles, Amo

INTRODUCTION - Intangibles, Amortization (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 12
Decrease in operating revenues	6
SOUTHERN POWER CO
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5
SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5
Gas Marketing Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	4
Wholesale Gas Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1

INTRODUCTION - Restricted Cash

INTRODUCTION - Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 2,164	$ 1,975
Restricted cash(a):
Total cash, cash equivalents, and restricted cash	2,168	1,978	$ 1,364	$ 1,519
Other accounts and notes receivable
Restricted cash(a):
Restricted cash	0	3
Other current assets
Restricted cash(a):
Restricted cash	3	0
SOUTHERN Co GAS
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	311	46
Restricted cash(a):
Total cash, cash equivalents, and restricted cash	314	49	$ 61	$ 70
SOUTHERN Co GAS | Other accounts and notes receivable
Restricted cash(a):
Restricted cash	0	3
SOUTHERN Co GAS | Other current assets
Restricted cash(a):
Restricted cash	$ 3	$ 0

REGULATORY MATTERS - Cost Recov

REGULATORY MATTERS - Cost Recovery Clauses (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
ALABAMA POWER CO | Other regulatory liabilities, current
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 35	$ 55
Retail Energy Cost Recovery	74	32
Natural Disaster Reserve	27	37
ALABAMA POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	17	7
Retail Energy Cost Recovery	22	17
Natural Disaster Reserve	104	113
ALABAMA POWER CO | Deferred under recovered regulatory clause revenues
Loss Contingencies [Line Items]
Rate CNP PPA	37	40
GEORGIA POWER CO | Other current liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	6	0
GEORGIA POWER CO | Other deferred credits and liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	163	73
MISSISSIPPI POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Property Damage Reserve	53	54
MISSISSIPPI POWER CO | Over recovered regulatory clause liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	25	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	38	0
SOUTHERN Co GAS | Other regulatory liabilities
Loss Contingencies [Line Items]
Natural Gas Cost Recovery	$ 84	$ 74

REGULATORY MATTERS - Georgia Po

REGULATORY MATTERS - Georgia Power (Details) - GEORGIA POWER CO $ in Millions	Mar. 09, 2020USD ($)
Public Utilities, General Disclosures [Line Items]
Requested decrease in fuel rates, percentage	16.00%
Requested decrease in fuel rates	$ 329

REGULATORY MATTERS - Nuclear Co

REGULATORY MATTERS - Nuclear Construction (Details) - GEORGIA POWER CO $ in Millions

Jan. 01, 2021

Apr. 15, 2020

Feb. 19, 2020USD ($)

Feb. 18, 2020USD ($)

Jan. 01, 2020

Jan. 11, 2018USD ($)

Jan. 01, 2016

Dec. 31, 2019USD ($)

Dec. 31, 2018appeal

Mar. 31, 2020USD ($)

Dec. 31, 2022USD ($)

Dec. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2012utilityMW

Dec. 31, 2009USD ($)

Jun. 30, 2019report

Aug. 31, 2018

Jun. 30, 2018USD ($)

Dec. 31, 2013

Loss Contingencies [Line Items]

Number of construction units approved | utility

2

Electric generating capacity in mega watts under consortium agreement | MW

1,100

Estimated in-service capital cost

$ 4,418

Financing costs collected, net of tax

$ 2,300

Increase (decrease) in NCCR tariff

$ (62)

Additional construction capital costs

$ 3,300

Amendment to estimated in-service capital cost

$ 5,680

Retail rate of return on common equity

10.95%

Number of appeals | appeal

2

Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Proportionate ownership share

45.70%

Construction contingency estimate, subject to rate recovery evaluation

$ 66

$ 366

Construction contingency estimate, subject to rate recovery evaluation, cumulative amount allocated to base capital cost forecast

206

Construction financing costs

2,300

Base project capital cost forecast, monthly

50

Monthly AFUDC

$ 10

Percentage of ownership interest required for voting for continuing construction

90.00%

Percentage of costs, disallowed for recovery

6.00%

Costs disallowed for recovery, period

6 months

Public utilities, extension project schedule, term

1 year

Production tax credits, aggregate purchase price, maximum

$ 300

Remaining share of construction costs, agreement to pay, percentage

100.00%

Preliminary estimated cost to complete

$ 8,400

Cost settlement agreement revised forecast, net of payments

$ 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

Plant Vogtle Units 3 And 4 | Scenario, Forecast

Loss Contingencies [Line Items]

Construction financing costs

$ 3,100

Public utilities, approved return on equity percentage

5.30%

Return on equity reduction, negative impact on earnings

$ 200

$ 255

$ 145

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 First Vogtle Construction Monitoring Report | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Number of approved VCM reports | report

21

Requested capital construction costs

$ 6,700

Guarantor obligations

1,700

Customer refund

$ 188

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

Loss Contingencies [Line Items]

Requested capital construction costs

$ 674

Maximum | COVID-19

Loss Contingencies [Line Items]

Estimate of possible loss

$ 20

Subsequent Event | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Expected percentage of positions eliminated

20.00%

Category I | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

800

Preliminary estimated cost to complete

$ 8,400

Category II | 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 | Plant Vogtle Units 3 And 4 | Vogtle Owners

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

44.30%

Category II | Minimum | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

$ 800

Category II | Maximum | Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Additional construction capital costs, threshold

$ 1,600

Category III | 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 | Plant Vogtle Units 3 And 4 | Vogtle Owners

Loss Contingencies [Line Items]

Percentage of construction costs, responsibility to pay

34.30%

Category III | Maximum | 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	3 Months Ended
	Mar. 31, 2020USD ($)
Loss Contingencies [Line Items]
Base project capital cost forecast	$ 8,200
Construction contingency estimate	200
Total project capital cost forecast	8,400
Net investment as of September 30, 2019	(6,200)
Remaining estimate to complete	2,200
Expected capitalized costs	270
Capitalized interest accrued	$ 36

REGULATORY MATTERS - Mississipp

REGULATORY MATTERS - Mississippi Power (Details) - MISSISSIPPI POWER CO - USD ($) $ in Millions	Apr. 27, 2020	Mar. 17, 2020
Loss Contingencies [Line Items]
Decrease in retail rates		$ 16.7
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
Subsequent Event
Loss Contingencies [Line Items]
Decrease in retail rates	$ 2

CONTINGENCIES - General Litigat

CONTINGENCIES - General Litigation Matters (Details) $ in Millions	1 Months Ended				12 Months Ended
	Sep. 30, 2019USD ($)	Mar. 31, 2019plaintiff	Nov. 30, 2018USD ($)defendantplaintiff	May 31, 2018USD ($)agreement	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 | Martin Product Sales, LLC Litigation
Loss Contingencies [Line Items]
Number of agreements | agreement				2
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
Martin Product Sales, LLC Litigation | Martin Product Sales, LLC Litigation
Loss Contingencies [Line Items]
Damages sought by litigation				$ 143
Compensatory damages sought by litigation	$ 5
Punitive damages sought by litigation	$ 50

CONTINGENCIES - Environmental R

CONTINGENCIES - Environmental Remediation (Details) - USD ($) $ in Millions	Mar. 31, 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	$ 262	$ 269

CONTINGENCIES - Other Matters (

CONTINGENCIES - Other Matters (Details) - USD ($) $ in Millions	Feb. 20, 2020	Dec. 31, 2018	Dec. 31, 2024	Dec. 31, 2020	Dec. 31, 2023	Jan. 15, 2024	Mar. 31, 2020
MISSISSIPPI POWER CO | Kemper IGCC
Loss Contingencies [Line Items]
Government grants received		$ 387
MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Asset retirement obligation, expected cost				$ 10
Liabilities incurred			$ 5	$ 17
GULF POWER CO | Scenario, Forecast | Plant Daniel Units 1 And 2
Loss Contingencies [Line Items]
Undivided ownership interest to be sold						50.00%
Undivided ownership interest, ownership interest in individual unit						100.00%
Minimum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Liabilities incurred					$ 15
Maximum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Liabilities incurred					$ 17
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

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Disaggregate Revenue Sources (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Operating revenues	$ 5,018	$ 5,412
Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	3,219	3,181
Residential
Disaggregation of Revenue [Line Items]
Operating revenues	1,370	1,327
Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	1,146	1,125
Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	680	708
Other
Disaggregation of Revenue [Line Items]
Operating revenues	23	21
Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	999	1,160
Residential
Disaggregation of Revenue [Line Items]
Operating revenues	496	601
Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	130	170
Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	264	256
Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	12	17
Other
Disaggregation of Revenue [Line Items]
Operating revenues	97	116
Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	315	352
PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	159	190
PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	105	107
Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	51	55
Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	566	952
Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	396	721
Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	163	221
Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	7	10
Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	192	266
Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	5,291	5,911
Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	868	1,361
Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	(1,141)	(1,860)
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	1,351	1,408
ALABAMA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	1,243	1,271
ALABAMA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	553	559
ALABAMA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	364	368
ALABAMA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	321	338
ALABAMA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	5	6
ALABAMA POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	73	118
ALABAMA POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	27	31
ALABAMA POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	27	27
ALABAMA POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	19	60
ALABAMA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
ALABAMA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	37	46
ALABAMA POWER CO | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	1,353	1,435
ALABAMA POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	(2)	(27)
ALABAMA POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	1,825	1,833
GEORGIA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	1,777	1,707
GEORGIA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	760	708
GEORGIA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	720	692
GEORGIA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	281	296
GEORGIA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	16	11
GEORGIA POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	23	27
GEORGIA POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	9	12
GEORGIA POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	12	13
GEORGIA POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	2	2
GEORGIA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
GEORGIA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	95	92
GEORGIA POWER CO | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	1,895	1,826
GEORGIA POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	(70)	7
GEORGIA POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	277	287
MISSISSIPPI POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	199	203
MISSISSIPPI POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	57	60
MISSISSIPPI POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	62	65
MISSISSIPPI POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	78	74
MISSISSIPPI POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	2	4
MISSISSIPPI POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	72	78
MISSISSIPPI POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	2	3
MISSISSIPPI POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	1	1
MISSISSIPPI POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	69	74
MISSISSIPPI POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
MISSISSIPPI POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	5	5
MISSISSIPPI POWER CO | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	276	286
MISSISSIPPI POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	1	1
MISSISSIPPI POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Operating revenues	375	443
SOUTHERN POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	249	273
SOUTHERN POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	125	151
SOUTHERN POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	66	81
SOUTHERN POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	58	41
SOUTHERN POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	3	4
SOUTHERN POWER CO | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	252	277
SOUTHERN POWER CO | Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	123	166
SOUTHERN POWER CO | Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Operating revenues	1,249	1,474
SOUTHERN Co GAS | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Operating revenues	999	1,160
SOUTHERN Co GAS | Residential
Disaggregation of Revenue [Line Items]
Operating revenues	496	601
SOUTHERN Co GAS | Commercial
Disaggregation of Revenue [Line Items]
Operating revenues	130	170
SOUTHERN Co GAS | Transportation
Disaggregation of Revenue [Line Items]
Operating revenues	264	256
SOUTHERN Co GAS | Industrial
Disaggregation of Revenue [Line Items]
Operating revenues	12	17
SOUTHERN Co GAS | Other
Disaggregation of Revenue [Line Items]
Operating revenues	97	116
SOUTHERN Co GAS | Wholesale electric revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | PPA energy revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	566	952
SOUTHERN Co GAS | Wholesale gas services
Disaggregation of Revenue [Line Items]
Operating revenues	396	721
SOUTHERN Co GAS | Gas marketing services
Disaggregation of Revenue [Line Items]
Operating revenues	163	221
SOUTHERN Co GAS | Other natural gas revenues
Disaggregation of Revenue [Line Items]
Operating revenues	7	10
SOUTHERN Co GAS | Other revenues
Disaggregation of Revenue [Line Items]
Operating revenues	0	0
SOUTHERN Co GAS | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	1,565	2,112
SOUTHERN Co GAS | Other revenue sources
Disaggregation of Revenue [Line Items]
Operating revenues	825	1,222
SOUTHERN Co GAS | Other adjustments
Disaggregation of Revenue [Line Items]
Operating revenues	$ (1,141)	$ (1,860)

REVENUE FROM CONTRACTS WITH C_4

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Contract Balances (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Receivables	$ 2,224	$ 2,413
Contract Assets	100	117
Contract Liabilities	49	52
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	518	586
Contract Assets	0	0
Contract Liabilities	7	10
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	697	688
Contract Assets	53	69
Contract Liabilities	11	13
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Receivables	70	79
Contract Assets	3	0
Contract Liabilities	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Receivables	86	97
Contract Assets	0	0
Contract Liabilities	1	1
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Receivables	696	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	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Contract assets	$ 100	$ 117
Contract liabilities	49	52
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract assets	36	40
Contract liabilities	29	28
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract assets	0	0
Contract liabilities	$ 7	10
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing	Georgia Power had contract assets primarily related to unregulated service agreements, where payment is contingent on project completion, and 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 the one-year contract term. Alabama Power had contract liabilities for outstanding performance obligations primarily related to extended service agreements. Contract liabilities for Georgia Power and Southern Power relate to cash collections recognized in advance of revenue for certain unregulated service agreements and certain levelized PPAs, respectively.
Contract assets	$ 53	69
Contract liabilities	11	13
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract assets	0	0
Contract liabilities	1	1
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract assets	3	0
Contract liabilities	$ 0	$ 0

REVENUE FROM CONTRACTS WITH C_6

REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Performance Obligations (Details) $ in Millions	Mar. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 367
Performance obligation, expected timing of satisfaction	9 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	$ 416
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	$ 354
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	$ 334
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	$ 314
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	$ 2,164
Performance obligation, expected timing of satisfaction
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 23
Performance obligation, expected timing of satisfaction	9 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]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 52
Performance obligation, expected timing of satisfaction	9 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	$ 66
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	$ 36
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	$ 34
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	$ 23
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	$ 61
Performance obligation, expected timing of satisfaction
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 224
Performance obligation, expected timing of satisfaction	9 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	$ 285
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	$ 287
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	$ 277
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	$ 285
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	$ 2,116
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
	Mar. 31, 2020	Mar. 31, 2019
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 3	$ 2
Lease income - operating leases	51	71
Variable lease income	74	66
Total lease income	128	139
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	6	7
Variable lease income	0	0
Total lease income	6	7
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	16	19
Variable lease income	0	0
Total lease income	16	19
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	3	2
Lease income - operating leases	0	0
Variable lease income	0	0
Total lease income	3	2
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	24	46
Variable lease income	80	75
Total lease income	104	121
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	9	9
Variable lease income	0	0
Total lease income	$ 9	$ 9

CONSOLIDATED ENTITIES AND EQU_3

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)investor	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Assets	$ 118,852	$ 118,700
Liabilities	86,645	86,650
Equity method investments	407	391
SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets	13,646	14,300
Liabilities	7,095	7,678
Equity method investments	45	28
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Assets	21,617	21,687
Liabilities	11,986	12,181
Equity method investments	$ 20	20
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%
Atlantic Coast Pipeline | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Ownership percentage, equity method investment	5.00%
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	381
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	2,500	2,500
Liabilities	123	128
Noncontrolling interests related to other partners' interests	$ 45	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	1,100
Liabilities	109	104
Noncontrolling interests related to other partners' interests	$ 396	$ 409

CONSOLIDATED ENTITIES AND EQU_4

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Balance Sheet Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,386	$ 1,303
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,333	1,251
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,216	1,137
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Investment Balance	85	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
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 42	$ 48
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	43	48
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	37	42
SOUTHERN Co GAS | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	3	3
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	2	2
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 1	$ 1

CONSOLIDATED ENTITIES AND EQU_6

CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Investment in SNG (Details) - SNG - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement Information
Revenues	$ 158	$ 166
Operating income	98	106
Net income	$ 75	$ 84

FINANCING - Schedule of Credit

FINANCING - Schedule of Credit Arrangements (Details)	Mar. 31, 2020USD ($)
Line of Credit Facility [Line Items]
Expires, 2020	$ 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	7,636,000,000
Due within One Year	33,000,000
Southern Company
Line of Credit Facility [Line Items]
Expires, 2020	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, 2020	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, 2020	0
Expires, 2022	0
Expires, 2023	0
Expires, 2024	1,750,000,000
Total	1,750,000,000
Unused	1,733,000,000
Due within One Year	0
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
Expires, 2020	0
Expires, 2022	150,000,000
Expires, 2023	125,000,000
Expires, 2024	0
Total	275,000,000
Unused	210,000,000
Due within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
Expires, 2020	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, 2023	60,000,000
Expires, 2021	120,000,000
Unused, 2021	25,000,000
Unused, 2022	60,000,000
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
Expires, 2020	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, 2020	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) - USD ($) $ in Millions	1 Months Ended
	Apr. 29, 2020	Mar. 31, 2020
Debt Instrument [Line Items]
Expires, 2023		$ 125
Variable rate pollution control revenue bonds outstanding		1,400
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Expires, 2023		125
Variable rate pollution control revenue bonds outstanding		40
ALABAMA POWER CO
Debt Instrument [Line Items]
Expires, 2023		0
Variable rate pollution control revenue bonds outstanding		854
GEORGIA POWER CO
Debt Instrument [Line Items]
Expires, 2023		0
Variable rate pollution control revenue bonds outstanding		550
Fixed rate pollution control revenue bonds outstanding		$ 188
Subsequent Event | MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Fixed rate pollution control revenue bonds purchased and held	$ 40

FINANCING - Shares Used to Comp

FINANCING - Shares Used to Compute Diluted Earnings Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
As reported shares (in shares)	1,057,000,000	1,038,000,000
Effect of stock-based compensation (in shares)	7,000,000	7,000,000
Effect of equity units (in shares)	3,000,000	0
Diluted shares (in shares)	1,067,000,000	1,045,000,000
Antidilutive securities excluded from computation of earnings per share (in shares)	0

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	14.70%	39.80%
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	4.60%	20.80%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	13.50%	(49.80%)

RETIREMENT BENEFITS (Details)

RETIREMENT BENEFITS (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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
Pension Plans and Postretirement Plans
Service cost	94,000,000	73,000,000
Interest cost	108,000,000	123,000,000
Expected return on plan assets	(275,000,000)	(221,000,000)
Amortization:
Prior service costs	1,000,000	0
Regulatory asset	0	0
Net (gain)/loss	67,000,000	30,000,000
Net periodic pension cost (income)	(5,000,000)	5,000,000
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	22,000,000	17,000,000
Interest cost	25,000,000	28,000,000
Expected return on plan assets	(66,000,000)	(51,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net (gain)/loss	18,000,000	9,000,000
Net periodic pension cost (income)	(1,000,000)	3,000,000
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	24,000,000	19,000,000
Interest cost	33,000,000	39,000,000
Expected return on plan assets	(87,000,000)	(73,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net (gain)/loss	22,000,000	11,000,000
Net periodic pension cost (income)	(8,000,000)	(4,000,000)
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	4,000,000	3,000,000
Interest cost	5,000,000	6,000,000
Expected return on plan assets	(13,000,000)	(10,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net (gain)/loss	3,000,000	1,000,000
Net periodic pension cost (income)	(1,000,000)	0
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000
Interest cost	1,000,000	1,000,000
Expected return on plan assets	(3,000,000)	(2,000,000)
Amortization:
Prior service costs	0	0
Regulatory asset	0	0
Net (gain)/loss	1,000,000	0
Net periodic pension cost (income)	1,000,000	1,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	8,000,000	6,000,000
Interest cost	8,000,000	9,000,000
Expected return on plan assets	(19,000,000)	(15,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)
Regulatory asset	4,000,000	3,000,000
Net (gain)/loss	2,000,000	1,000,000
Net periodic pension cost (income)	2,000,000	3,000,000
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	5,000,000	5,000,000
Interest cost	13,000,000	17,000,000
Expected return on plan assets	(18,000,000)	(16,000,000)
Amortization:
Prior service costs		1,000,000
Regulatory asset	0	0
Net (gain)/loss	1,000,000	(1,000,000)
Net periodic pension cost (income)	1,000,000	6,000,000
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	1,000,000
Interest cost	3,000,000	4,000,000
Expected return on plan assets	(7,000,000)	(6,000,000)
Amortization:
Prior service costs		1,000,000
Regulatory asset	0	0
Net (gain)/loss	0	0
Net periodic pension cost (income)	(2,000,000)	0
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000
Interest cost	5,000,000	7,000,000
Expected return on plan assets	(7,000,000)	(6,000,000)
Amortization:
Prior service costs		0
Regulatory asset	0	0
Net (gain)/loss	1,000,000	0
Net periodic pension cost (income)	0	2,000,000
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	0	1,000,000
Expected return on plan assets	0	0
Amortization:
Prior service costs		0
Regulatory asset	0	0
Net (gain)/loss	0	0
Net periodic pension cost (income)	0	1,000,000
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	0	0
Expected return on plan assets	0	0
Amortization:
Prior service costs		0
Regulatory asset	0	0
Net (gain)/loss	0	0
Net periodic pension cost (income)	0	0
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	1,000,000
Interest cost	2,000,000	2,000,000
Expected return on plan assets	(2,000,000)	(2,000,000)
Amortization:
Prior service costs		0
Regulatory asset	2,000,000	2,000,000
Net (gain)/loss	(1,000,000)	(1,000,000)
Net periodic pension cost (income)	$ 1,000,000	$ 2,000,000

FAIR VALUE MEASUREMENTS - Asset

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets:
Derivatives	$ 218	$ 233
Liabilities:
Derivatives	249	189
Collateral already posted, aggregate fair value	128
Weather derivative premium	16
ALABAMA POWER CO
Assets:
Derivatives	1	2
Liabilities:
Derivatives	23	22
GEORGIA POWER CO
Assets:
Derivatives	0	1
Investments in trusts	31
Liabilities:
Derivatives	55	67
MISSISSIPPI POWER CO
Assets:
Derivatives	0	0
Liabilities:
Derivatives	30	26
SOUTHERN POWER CO
Assets:
Derivatives	2	19
Liabilities:
Derivatives	93	27
SOUTHERN Co GAS
Assets:
Derivatives	193	212
Liabilities:
Derivatives	48	41
Total
Collateral already posted, aggregate fair value	128	99
Weather derivative premium	16	$ 4
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	1,697
Other investments	38
Total	4,147
Liabilities:
Contingent consideration	19
Total	780
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	1,686
Other investments	9
Total	2,700
Liabilities:
Contingent consideration	0
Total	426
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	11
Other investments	29
Total	1,300
Liabilities:
Contingent consideration	0
Total	324
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Other investments	0
Total	87
Liabilities:
Contingent consideration	19
Total	30
Fair Value, Measurements, Recurring | Net Asset Value as a Practical Expedient (NAV)
Assets:
Total	60
Fair Value, Measurements, Recurring | Energy-related derivatives
Assets:
Derivatives	579
Liabilities:
Derivatives	649
Fair Value, Measurements, Recurring | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	328
Liabilities:
Derivatives	426
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	164
Liabilities:
Derivatives	212
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	87
Liabilities:
Derivatives	11
Fair Value, Measurements, Recurring | Interest rate derivatives
Assets:
Derivatives	22
Liabilities:
Derivatives	22
Fair Value, Measurements, Recurring | Interest rate derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Interest rate derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	22
Liabilities:
Derivatives	22
Fair Value, Measurements, Recurring | Interest rate derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	0
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Foreign currency derivatives
Liabilities:
Derivatives	90
Fair Value, Measurements, Recurring | Foreign currency derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Foreign currency derivatives | Significant Other Observable Inputs (Level 2)
Liabilities:
Derivatives	90
Fair Value, Measurements, Recurring | Foreign currency derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | Domestic equity
Assets:
Investments in trusts	686
Fair Value, Measurements, Recurring | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	578
Fair Value, Measurements, Recurring | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	108
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	223
Fair Value, Measurements, Recurring | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	52
Fair Value, Measurements, Recurring | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	171
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	289
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	289
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	103
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	103
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	16
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	16
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	320
Fair Value, Measurements, Recurring | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	23
Fair Value, Measurements, Recurring | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	297
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	85
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	85
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	60
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	60
Fair Value, Measurements, Recurring | Other
Assets:
Investments in trusts	29
Fair Value, Measurements, Recurring | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	24
Fair Value, Measurements, Recurring | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	5
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	705
Other investments	29
Total	1,592
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	694
Other investments	0
Total	1,144
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	11
Other investments	29
Total	388
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	60
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives
Assets:
Derivatives	5
Liabilities:
Derivatives	27
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	5
Liabilities:
Derivatives	27
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	467
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	368
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	99
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	102
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	52
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	50
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	22
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	22
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	164
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	23
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	141
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	30
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	30
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	60
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	60
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other
Assets:
Investments in trusts	7
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	7
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	212
Total	1,150
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	212
Total	438
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	712
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	6
Liabilities:
Derivatives	61
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	6
Liabilities:
Derivatives	61
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	211
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	210
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	119
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	119
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	267
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	267
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	102
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	102
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	156
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	156
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	56
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	56
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	21
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	16
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	5
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	79
Total	82
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	79
Total	79
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	3
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	3
Liabilities:
Derivatives	33
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	3
Liabilities:
Derivatives	33
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	166
Total	168
Liabilities:
Contingent consideration	19
Total	112
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	166
Total	166
Liabilities:
Contingent consideration	0
Total	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	2
Liabilities:
Contingent consideration	0
Total	93
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	2
Liabilities:
Derivatives	3
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	2
Liabilities:
Derivatives	3
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
Liabilities:
Derivatives	90
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Significant Other Observable Inputs (Level 2)
Liabilities:
Derivatives	90
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS
Assets:
Cash equivalents	270
Total	861
Liabilities:
Total	546
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	270
Total	598
Liabilities:
Total	426
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	176
Liabilities:
Total	109
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	87
Liabilities:
Total	11
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives
Assets:
Derivatives	563
Liabilities:
Derivatives	525
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	328
Liabilities:
Derivatives	426
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	148
Liabilities:
Derivatives	88
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	87
Liabilities:
Derivatives	11
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Interest rate derivatives
Liabilities:
Derivatives	21
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Interest rate derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Interest rate derivatives | Significant Other Observable Inputs (Level 2)
Liabilities:
Derivatives	21
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Interest rate derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Domestic equity
Assets:
Non-qualified deferred compensation trusts	9
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	9
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	16
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	16
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 - Sched

FAIR VALUE MEASUREMENTS - Schedule of Increase (Decrease) In Fair Value Of Funds (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ (247)	$ 152
ALABAMA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	(167)	87
GEORGIA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ (80)	$ 65

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Mar. 31, 2020USD ($)$ / MMBTU
ALABAMA POWER CO | Private equity
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	$ 60
Unfunded commitments	73
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	$ 76
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	(0.84)
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	0.21

FAIR VALUE MEASUREMENTS - Finan

FAIR VALUE MEASUREMENTS - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions	Mar. 31, 2020USD ($)
Long-term debt, including securities due within one year:
Carrying amount	$ 45,820
Fair value	49,126
ALABAMA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	8,432
Fair value	9,239
GEORGIA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	12,217
Fair value	14,020
MISSISSIPPI POWER CO
Long-term debt, including securities due within one year:
Carrying amount	1,413
Fair value	1,433
SOUTHERN POWER CO
Long-term debt, including securities due within one year:
Carrying amount	4,369
Fair value	4,376
SOUTHERN Co GAS
Long-term debt, including securities due within one year:
Carrying amount	5,836
Fair value	$ 6,416

FAIR VALUE MEASUREMENTS - Fair

FAIR VALUE MEASUREMENTS - Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component (Details) - SOUTHERN Co GAS $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 14
Transfers to Level 3	70
Transfers from Level 3	(3)
Instruments realized or otherwise settled during period	(1)
Changes in fair value	(4)
Ending balance	$ 76

DERIVATIVES - Energy-Related De

DERIVATIVES - Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Mar. 31, 2020MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	945
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	88
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	168
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	100
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	4
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	585
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	4,000

DERIVATIVES - Narrative (Detail

DERIVATIVES - Narrative (Details) MWh in Millions, MMBTU in Millions	3 Months Ended
	Mar. 31, 2020USD ($)MMBTU	Dec. 31, 2019USD ($)MWh
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	23
Cash flow hedge gain (loss) to be reclassified within twelve months | $	$ (25,000,000)
Collateral already posted, aggregate fair value | $	$ 128,000,000
ALABAMA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	6
GEORGIA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	7
MISSISSIPPI POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	3
SOUTHERN POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	7
Registrants | Derivative Counterparties
Derivative [Line Items]
Collateral already posted, aggregate fair value | $	$ 0
SOUTHERN Co GAS
Derivative [Line Items]
Collateral already posted, aggregate fair value | $	128,000,000	$ 99,000,000
Parent Company and Southern Power
Derivative [Line Items]
Foreign currency cash flow hedge gain (loss) to be reclassified during next 12 months | $	$ (24,000,000)
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	3 Months Ended
	Mar. 31, 2020USD ($)
Derivative [Line Items]
Notional Amount	$ 2,060,000,000
Fair Value Gain (Loss) at March 31, 2020	1,000,000
September 2030 | SOUTHERN Co GAS | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Notional Amount	$ 200,000,000
Weighted Average Interest Rate Paid	1.81%
Fair Value Gain (Loss) at March 31, 2020	$ (21,000,000)
December 2021 | MISSISSIPPI POWER CO | Cash Flow Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 60,000,000
Weighted Average Interest Rate Paid	0.58%
Fair Value Gain (Loss) at March 31, 2020	$ 0
June 2020 | Southern Company | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 300,000,000
Interest Rate Received	2.75%
Fair Value Gain (Loss) at March 31, 2020	$ 1,000,000
July 2021 | Southern Company | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 1,500,000,000
Interest Rate Received	2.35%
Fair Value Gain (Loss) at March 31, 2020	$ 21,000,000
London Interbank Offered Rate (LIBOR) | June 2020 | Southern Company | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Weighted Average Interest Rate Paid	0.92%
London Interbank Offered Rate (LIBOR) | July 2021 | 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) - 3 months ended Mar. 31, 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 March 31, 2020	(90)
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 March 31, 2020	$ (39)
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 March 31, 2020	$ (51)

DERIVATIVES - Derivative Financ

DERIVATIVES - Derivative Financial Statement Presentation and Amounts With Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivatives, assets	$ 601	$ 696
Derivatives, liabilities	760	751
Derivative asset, Gross amounts offset	(383)	(463)
Derivative liability, Gross amounts offset	(511)	(562)
Derivative asset	218	233
Derivative liability	249	189
Collateral already posted, aggregate fair value	128
Weather derivative premium	16
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	561	668
Derivatives, liabilities	503	583
Derivatives not designated as hedging instruments | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	300	461
Derivatives not designated as hedging instruments | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	297	358
Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	261	207
Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	206	225
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	15	9
Derivatives, liabilities	140	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	7	3
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	100	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	8	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	40	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	25	19
Derivatives, liabilities	117	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	3	1
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 liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	6	6
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	12	2
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 liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	21	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	10	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 | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	24	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	0	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	66	0
ALABAMA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	4
Derivatives, liabilities	27	24
Derivative asset, Gross amounts offset	(4)	(2)
Derivative liability, Gross amounts offset	(4)	(2)
Derivative asset	1	2
Derivative liability	23	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	5	4
Derivatives, liabilities	27	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	3	2
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	18	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	2	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	9	10
GEORGIA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	6	4
Derivatives, liabilities	61	70
Derivative asset, Gross amounts offset	(6)	(3)
Derivative liability, Gross amounts offset	(6)	(3)
Derivative asset	0	1
Derivative liability	55	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	6	4
Derivatives, liabilities	61	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	3	1
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	42	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	3	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	19	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 | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	17
MISSISSIPPI POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	3	1
Derivatives, liabilities	33	27
Derivative asset, Gross amounts offset	(3)	(1)
Derivative liability, Gross amounts offset	(3)	(1)
Derivative asset	0	0
Derivative liability	30	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	3	1
Derivatives, liabilities	33	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	1	0
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	21	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	2	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	12	12
SOUTHERN POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	19
Derivatives, liabilities	93	27
Derivative asset, Gross amounts offset	0	0
Derivative liability, Gross amounts offset	0	0
Derivative asset	2	19
Derivative liability	93	27
SOUTHERN POWER CO | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	2
Derivatives, liabilities	1	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 | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	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	2	17
Derivatives, liabilities	92	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	2	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 | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	2
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 | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	24	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	0	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	66	0
SOUTHERN Co GAS
Derivatives, Fair Value [Line Items]
Derivatives, assets	563	668
Derivatives, liabilities	546	596
Derivative asset, Gross amounts offset	(370)	(456)
Derivative liability, Gross amounts offset	(498)	(555)
Derivative asset	193	212
Derivative liability	48	41
Collateral already posted, aggregate fair value	128	99
Weather derivative premium	16	4
SOUTHERN Co GAS | Energy-related derivatives
Derivatives, Fair Value [Line Items]
Collateral already posted, aggregate fair value	19	11
SOUTHERN Co GAS | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	561	666
Derivatives, liabilities	502	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	261	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	206	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	300	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	296	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	1	0
Derivatives, liabilities	19	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	1	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	0	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	19	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	1	2
Derivatives, liabilities	25	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 | Assets from risk management activities
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 | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	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	$ 21	$ 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
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	$ 128
Gain (Loss) Recognized in OCI on Derivative	(113)	$ (39)
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	128		$ 99
Gain (Loss) Recognized in OCI on Derivative	(27)	0
Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(107)		(94)
Gain (Loss) Recognized in OCI on Derivative	(4)	0
Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(79)		(63)
Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(33)		(37)
Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	5		6
Energy-related derivatives | ALABAMA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(23)		(20)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(17)		(14)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(7)		(8)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	1		2
Energy-related derivatives | GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(55)		(49)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(39)		(31)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(16)		(18)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0
Energy-related derivatives | MISSISSIPPI POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(29)		(26)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(19)		(15)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(10)		(11)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0
Energy-related derivatives | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		1
Collateral already posted, aggregate fair value	19		11
Gain (Loss) Recognized in OCI on Derivative	(4)	0
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(4)		(3)
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	4		$ 4
Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(26)	0
Interest rate derivatives | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(23)	0
Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(83)	(39)
Foreign currency derivatives | SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	$ (83)	$ (39)

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
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Total cost of natural gas	$ 439	$ 686
Depreciation and amortization	857	751
Total interest expense, net of amounts capitalized	(456)	(430)
Total other income (expense), net	103	78
Cash Flow Hedging | Energy-related derivatives | Cost of natural gas
Derivative [Line Items]
Gain (loss) on hedge	(7)	1
Cash Flow Hedging | Energy-related derivatives | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	(3)
Cash Flow Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(5)
Cash Flow Hedging | Foreign currency derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(6)
Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	(31)	(24)
Fair Value Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	29	14
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	117	119
Total interest expense, net of amounts capitalized	(39)	(44)
Total other income (expense), net	2	2
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	(3)
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)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	$ (31)	$ (24)

DERIVATIVES - Cumulative Basis

DERIVATIVES - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Fair Value Hedging - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Securities due within one year
Derivative [Line Items]
Carrying Amount of the Hedged Item	$ (600)	$ (599)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	(1)	0
Long-term debt
Derivative [Line Items]
Carrying Amount of the Hedged Item	(1,519)	(1,494)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	$ (22)	$ 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
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 77	$ 41
Natural gas revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	70	33
Cost of natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 7	$ 8

ACQUISITIONS AND DISPOSITIONS -

ACQUISITIONS AND DISPOSITIONS - Southern Power Narrative (Details) $ in Millions	Jan. 17, 2020USD ($)	Mar. 31, 2020USD ($)agreementfacilityMW	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)	May 31, 2019MW
Business Acquisition [Line Items]
Construction work in progress		$ 8,360		$ 7,880
Preliminary gain		$ 38	$ 2,503
SOUTHERN POWER CO
Business Acquisition [Line Items]
Approximate nameplate capacity (MW) | MW		300
Business acquisition, number of Power Purchase Agreements | agreement		2
Construction work in progress		$ 534		$ 515
Preliminary gain		39	$ 0
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Mankato expansion
Business Acquisition [Line Items]
Approximate nameplate capacity (MW) | MW					385
Gain on sale		$ 39
Nacogdoches biomass-fueled facility	$ 663
Preliminary gain	39
After tax gain	$ 23
SOUTHERN POWER CO | Series of Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of facilities under construction | facility		2
SOUTHERN POWER CO | Series of Construction Projects
Business Acquisition [Line Items]
Construction work in progress		$ 447
SOUTHERN POWER CO | Series of Construction Projects | Minimum
Business Acquisition [Line Items]
Estimated future construction payments		490
SOUTHERN POWER CO | Series of Construction Projects | Maximum
Business Acquisition [Line Items]
Estimated future construction payments		$ 535

ACQUISITIONS AND DISPOSITIONS_2

ACQUISITIONS AND DISPOSITIONS - Schedule of Construction Projects (Details) - SOUTHERN POWER CO - MW	1 Months Ended	6 Months Ended
	May 31, 2020	Dec. 31, 2020	Mar. 31, 2020	Oct. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)			300
Reading | Reading
Business Acquisition [Line Items]
Ownership percentage by parent					100.00%
Reading | Reading | Class B Membership Interest
Business Acquisition [Line Items]
Ownership percentage by parent					100.00%
Skookumchuck | Skookumchuck
Business Acquisition [Line Items]
Ownership percentage by parent				100.00%
Scenario, Forecast | Reading
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)	200
PPA Contract Period	12 years
Scenario, Forecast | Skookumchuck
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)		136
PPA Contract Period		20 years

ACQUISITIONS AND DISPOSITIONS_3

ACQUISITIONS AND DISPOSITIONS - Southern Company Gas Narrative (Details) - SOUTHERN Co GAS $ in Millions	Mar. 24, 2020USD ($)payment
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 and Atlantic Coast Pipeline
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of contingent milestone payments | payment	2
Contingent milestone payment, amount	$ 5

ACQUISITIONS AND DISPOSITIONS_4

ACQUISITIONS AND DISPOSITIONS - Pre-tax Profit (Details) - SOUTHERN POWER CO - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Plant Nacogdoches
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes		$ 6
Plant Mankato
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	$ 2	$ 1

SEGMENT AND RELATED INFORMATI_3

SEGMENT AND RELATED INFORMATION - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)statesegment	Mar. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	3
Total operating revenues	$ 5,018	$ 5,412
Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	1,249	1,474
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Total operating revenues	375	443
SOUTHERN POWER CO | Traditional Electric Operating Companies | Wholesale revenues, affiliates
Segment Reporting Information [Line Items]
Total operating revenues	$ 86	87
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	4
Total operating revenues	$ 1,249	1,474
Number of reportable segments | segment	4
SOUTHERN Co GAS | Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	$ 1,240	1,476
SOUTHERN Co GAS | SOUTHERN POWER CO | Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	$ 10	$ 17
Southern Natural Gas Company, LLC | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%
PennEast Pipelines | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	20.00%
Dalton Pipeline | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%
Atlantic Coast Pipeline | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	5.00%

SEGMENT AND RELATED INFORMATI_4

SEGMENT AND RELATED INFORMATION - Financial Data for Business Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 5,018	$ 5,412
Segment net income (loss)	868	2,084
Goodwill	5,280		$ 5,280
Total assets	118,852		118,700
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	375	443
Segment net income (loss)	75	56
Total assets	13,646		14,300
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
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,249	1,474
Segment net income (loss)	275	270
Goodwill	5,015		5,015
Total assets	21,617		21,687
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	3,695	3,795
Segment net income (loss)	717	621
Goodwill	2		2
Total assets	94,716		94,650
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,249	1,474
All Other | Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Segment Reporting Information [Line Items]
Preliminary pre-tax gain		2,500
Preliminary after-tax gain		1,300
Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	4,034
Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	981
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,256	1,495
Segment net income (loss)	274	273
Total assets	21,978		22,228
Operating Segments | Traditional Electric Operating Companies | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	3,407	3,445
Segment net income (loss)	642	565
Goodwill	0		0
Total assets	81,765		81,063
Operating Segments | SOUTHERN POWER CO | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	375	443
Segment net income (loss)	75	56
Goodwill	2		2
Total assets	13,646		14,300
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,249	1,474
Segment net income (loss)	275	270
Goodwill	5,015		5,015
Total assets	21,617		21,687
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	114	182
Segment net income (loss)	(121)	1,195
Goodwill	263		263
Total assets	3,467		3,511
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8	11
Segment net income (loss)	1	(3)
Total assets	11,094		10,759
Operating Segments | Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,020	1,172
Segment net income (loss)	164	133
Total assets	18,166		18,204
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8	8
Segment net income (loss)	30	32
Total assets	1,652		1,678
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	51	86
Segment net income (loss)	23	47
Total assets	643		850
Operating Segments | Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	177	229
Segment net income (loss)	57	61
Total assets	1,517		1,496
Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(40)	(39)
Segment net income (loss)	(3)	(2)
Goodwill	0		0
Total assets	(948)		(1,148)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(15)	(32)
Segment net income (loss)	0	0
Total assets	(11,455)		(11,300)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(87)	(93)
Segment net income (loss)	0	$ 0
Goodwill	0		0
Total assets	$ (695)		$ (713)

SEGMENT AND RELATED INFORMATI_5

SEGMENT AND RELATED INFORMATION - Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Concentration Risk [Line Items]
Operating revenues	$ 5,018	$ 5,412
Less Gross Gas Costs	439	686
Retail
Concentration Risk [Line Items]
Operating revenues	3,078	3,084
Wholesale
Concentration Risk [Line Items]
Operating revenues	418	499
Other
Concentration Risk [Line Items]
Operating revenues	151	168
Electric Utilities' Revenues
Concentration Risk [Line Items]
Operating revenues	3,695	3,795
Electric Utilities' Revenues | Retail
Concentration Risk [Line Items]
Operating revenues	3,078	3,084
Electric Utilities' Revenues | Wholesale
Concentration Risk [Line Items]
Operating revenues	418	499
Electric Utilities' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	199	212
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	1,249	1,474
Southern Company Gas' Revenues | Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	1,013	1,161
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	51	86
Southern Company Gas' Revenues | Gas Marketing Services
Concentration Risk [Line Items]
Operating revenues	177	229
Southern Company Gas' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	8	(2)
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	1,249	1,474
Operating Segments | Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	1,249	1,474
Operating Segments | Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	1,256	1,495
Operating Segments | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	51	86
Less Gross Gas Costs	1,163	1,928
Operating Segments | Third Party Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	1,185	1,926
Operating Segments | Intercompany Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	29	88
Operating Segments | Total Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	$ 1,214	$ 2,014