Mississippi Power (MSPWP) 10-Q 30 Oct 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2019shares
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
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)	1,048,733,989
Entity Central Index Key	0000092122
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Emerging Growth Company	false
Entity Small Business	false
Common Stock, par value $5 per share
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $5 per share
Trading Symbol	SO
Security Exchange Name	NYSE
Series 2015A 6.25% Junior Subordinated Notes due 2075
Document Information [Line Items]
Title of 12(b) Security	Series 2015A 6.25% Junior Subordinated Notes due 2075
Trading Symbol	SOJA
Security Exchange Name	NYSE
Series 2016A 5.25% Junior Subordinated Notes due 2076
Document Information [Line Items]
Title of 12(b) Security	Series 2016A 5.25% Junior Subordinated Notes due 2076
Trading Symbol	SOJB
Security Exchange Name	NYSE
Series 2017B 5.25% Junior Subordinated Notes due 2077
Document Information [Line Items]
Title of 12(b) Security	Series 2017B 5.25% Junior Subordinated Notes due 2077
Trading Symbol	SOJC
Security Exchange Name	NYSE
2019 Series A Corporate Units
Document Information [Line Items]
Title of 12(b) Security	2019 Series A Corporate Units
Trading Symbol	SOLN
Security Exchange Name	NYSE
ALABAMA POWER CO
Document Information [Line Items]
Entity File Number	1-3164
Entity Registrant Name	Alabama Power Company
Entity Tax Identification Number	63-0004250
Entity Incorporation, State or Country Code	AL
Entity Address, Address Line One	600 North 18th Street
Entity Address, City or Town	Birmingham
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35203
City Area Code	205
Local Phone Number	257-1000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	30,537,500
Entity Central Index Key	0000003153
Entity Emerging Growth Company	false
Entity Small Business	false
ALABAMA POWER CO | 5.00% Series Class A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	5.00% Series Class A Preferred Stock
Trading Symbol	ALP PR Q
Security Exchange Name	NYSE
GEORGIA POWER CO
Document Information [Line Items]
Entity File Number	1-6468
Entity Registrant Name	Georgia Power Company
Entity Tax Identification Number	58-0257110
Entity Incorporation, State or Country Code	GA
Entity Address, Address Line One	241 Ralph McGill Boulevard, N.E.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30308
City Area Code	404
Local Phone Number	506-6526
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	9,261,500
Entity Central Index Key	0000041091
Entity Emerging Growth Company	false
Entity Small Business	false
GEORGIA POWER CO | Series 2017A 5.00% Junior Subordinated Notes due 2077
Document Information [Line Items]
Title of 12(b) Security	Series 2017A 5.00% Junior Subordinated Notes due 2077
Trading Symbol	GPJA
Security Exchange Name	NYSE
MISSISSIPPI POWER CO
Document Information [Line Items]
Entity File Number	001-11229
Entity Registrant Name	Mississippi Power Company
Entity Tax Identification Number	64-0205820
Entity Incorporation, State or Country Code	MS
Entity Address, Address Line One	2992 West Beach Boulevard
Entity Address, City or Town	Gulfport
Entity Address, State or Province	MS
Entity Address, Postal Zip Code	39501
City Area Code	228
Local Phone Number	864-1211
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	1,121,000
Entity Central Index Key	0000066904
Entity Emerging Growth Company	false
Entity Small Business	false
SOUTHERN POWER CO
Document Information [Line Items]
Entity File Number	001-37803
Entity Registrant Name	Southern Power Company
Entity Tax Identification Number	58-2598670
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	30 Ivan Allen Jr. Boulevard, N.W.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30308
City Area Code	404
Local Phone Number	506-5000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	1,000
Entity Central Index Key	0001160661
Entity Emerging Growth Company	false
Entity Small Business	false
SOUTHERN POWER CO | Series 2016A 1.000% Senior Notes due 2022
Document Information [Line Items]
Title of 12(b) Security	Series 2016A 1.000% Senior Notes due 2022
Trading Symbol	SO/22B
Security Exchange Name	NYSE
SOUTHERN POWER CO | Series 2016B 1.850% Senior Notes due 2026
Document Information [Line Items]
Title of 12(b) Security	Series 2016B 1.850% Senior Notes due 2026
Trading Symbol	SO/26A
Security Exchange Name	NYSE
SOUTHERN Co GAS
Document Information [Line Items]
Entity File Number	1-14174
Entity Registrant Name	Southern Company Gas
Entity Tax Identification Number	58-2210952
Entity Incorporation, State or Country Code	GA
Entity Address, Address Line One	Ten Peachtree Place, N.E.
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30309
City Area Code	404
Local Phone Number	584-4000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	100
Entity Central Index Key	0001004155
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating Revenues:
Total operating revenues	$ 5,995	$ 6,159	$ 16,505	$ 18,158
Operating Expenses:
Other operations and maintenance	1,292	1,404	3,888	4,217
Depreciation and amortization	760	787	2,267	2,338
Taxes other than income taxes	303	319	931	990
Estimated loss on plants under construction	4	1	10	1,105
Impairment charges	110	36	142	197
(Gain) loss on dispositions, net	(6)	(353)	(2,512)	(317)
Total operating expenses	3,982	3,985	9,459	14,545
Operating Income (Loss)	2,013	2,174	7,046	3,613
Other Income and (Expense):
Allowance for equity funds used during construction	33	36	96	99
Earnings from equity method investments	39	36	120	108
Interest expense, net of amounts capitalized	(434)	(458)	(1,294)	(1,386)
Other income (expense), net	61	57	239	195
Total other income and (expense)	(301)	(329)	(839)	(984)
Earnings (Loss) Before Income Taxes	1,712	1,845	6,207	2,629
Income taxes	367	623	1,872	598
Consolidated Net Income	1,345	1,222	4,335	2,031
Dividends on preferred stock of subsidiaries	4	4	11	12
Net income attributable to noncontrolling interests	25	54	26	71
Net Income (Loss)	$ 1,316	$ 1,164	$ 4,298	$ 1,948
Earnings per share -
Basic (in dollars per share)	$ 1.26	$ 1.14	$ 4.12	$ 1.92
Diluted (in dollars per share)	$ 1.25	$ 1.13	$ 4.09	$ 1.91
Average number of shares of common stock outstanding (in millions)
Basic (in shares)	1,048	1,023	1,043	1,016
Diluted (in shares)	1,057	1,029	1,051	1,021
Retail electric revenues
Operating Revenues:
Total operating revenues	$ 4,512	$ 4,605	$ 11,136	$ 11,913
Wholesale electric revenues
Operating Revenues:
Total operating revenues	625	698	1,667	1,937
Other electric revenues
Operating Revenues:
Total operating revenues	163	165	492	495
Natural gas
Operating Revenues:
Total operating revenues	498	492	2,661	2,806
Operating Expenses:
Total cost of natural gas	79	104	956	1,053
Other
Operating Revenues:
Total operating revenues	197	199	549	1,007
Operating Expenses:
Total cost of natural gas	114	120	316	688
Fuel
Operating Expenses:
Total cost of natural gas	1,072	1,310	2,836	3,514
Purchased power
Operating Expenses:
Total cost of natural gas	254	257	625	760
Alternative revenue programs
Operating Revenues:
Total operating revenues	0	5	0	(23)
ALABAMA POWER CO
Operating Revenues:
Total operating revenues	1,841	1,740	4,762	4,716
Operating Expenses:
Other operations and maintenance	409	401	1,221	1,191
Depreciation and amortization	195	192	593	570
Taxes other than income taxes	101	97	301	289
Total operating expenses	1,165	1,179	3,303	3,403
Operating Income (Loss)	676	561	1,459	1,313
Other Income and (Expense):
Allowance for equity funds used during construction	13	16	41	43
Interest expense, net of amounts capitalized	(83)	(82)	(248)	(240)
Other income (expense), net	11	9	36	24
Total other income and (expense)	(59)	(57)	(171)	(173)
Earnings (Loss) Before Income Taxes	617	504	1,288	1,140
Income taxes	144	127	295	272
Consolidated Net Income	473	377	993	868
Dividends on preferred stock of subsidiaries	4	4	11	11
Net Income (Loss)	469	373	982	857
ALABAMA POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	1,694	1,584	4,286	4,208
ALABAMA POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	71	74	194	213
ALABAMA POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	2	14	66	96
ALABAMA POWER CO | Other
Operating Revenues:
Total operating revenues	74	68	216	199
ALABAMA POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	310	356	864	1,028
ALABAMA POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	77	64	160	176
ALABAMA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of natural gas	73	69	164	149
GEORGIA POWER CO
Operating Revenues:
Total operating revenues	2,755	2,593	6,706	6,601
Operating Expenses:
Other operations and maintenance	473	460	1,385	1,325
Depreciation and amortization	250	232	733	690
Taxes other than income taxes	127	118	348	332
Estimated loss on plants under construction	0	0	0	1,060
Total operating expenses	1,594	1,602	4,451	5,569
Operating Income (Loss)	1,161	991	2,255	1,032
Other Income and (Expense):
Allowance for equity funds used during construction			49	50
Interest expense, net of amounts capitalized	(103)	(95)	(304)	(303)
Other income (expense), net	36	30	113	104
Total other income and (expense)	(67)	(65)	(191)	(199)
Earnings (Loss) Before Income Taxes	1,094	926	2,064	833
Income taxes	255	262	466	212
Consolidated Net Income	839	664	1,598	621
Net Income (Loss)	839	664
GEORGIA POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	2,567	2,425	6,181	6,112
GEORGIA POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	36	43	98	123
GEORGIA POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	3	4	9	17
GEORGIA POWER CO | Other
Operating Revenues:
Total operating revenues	149	121	418	349
GEORGIA POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	443	480	1,132	1,269
GEORGIA POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	151	106	393	338
GEORGIA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of natural gas	150	206	460	555
MISSISSIPPI POWER CO
Operating Revenues:
Total operating revenues	370	358	970	956
Operating Expenses:
Other operations and maintenance	68	80	194	222
Depreciation and amortization	48	42	144	126
Taxes other than income taxes	30	28	85	83
Estimated loss on plants under construction	4	1	10	45
Total operating expenses	277	278	767	815
Operating Income (Loss)	93	80	203	141
Other Income and (Expense):
Interest expense, net of amounts capitalized	(17)	(19)	(52)	(59)
Other income (expense), net	4	0	15	28
Total other income and (expense)	(13)	(19)	(37)	(31)
Earnings (Loss) Before Income Taxes	80	61	166	110
Income taxes	15	14	27	23
Consolidated Net Income	65	47	139	87
Dividends on preferred stock of subsidiaries	0	0	0	1
Net Income (Loss)	65	47	139	86
MISSISSIPPI POWER CO | Retail electric revenues
Operating Revenues:
Total operating revenues	251	254	669	660
MISSISSIPPI POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	64	70	178	197
MISSISSIPPI POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	51	28	109	81
MISSISSIPPI POWER CO | Other
Operating Revenues:
Total operating revenues	4	6	14	18
MISSISSIPPI POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	121	116	319	312
MISSISSIPPI POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	6	11	15	27
SOUTHERN POWER CO
Operating Revenues:
Total operating revenues	574	635	1,527	1,699
Operating Expenses:
Other operations and maintenance	85	94	250	278
Depreciation and amortization	120	130	357	370
Taxes other than income taxes	10	12	32	36
Impairment charges	0	36	0	155
(Gain) loss on dispositions, net	0	0	(23)	0
Total operating expenses	407	499	1,147	1,487
Operating Income (Loss)	167	136	380	212
Other Income and (Expense):
Interest expense, net of amounts capitalized	(43)	(45)	(127)	(138)
Other income (expense), net	6	17	48	22
Total other income and (expense)	(37)	(28)	(79)	(116)
Earnings (Loss) Before Income Taxes	130	108	301	96
Income taxes	19	(38)	(41)	(210)
Consolidated Net Income	111	146	342	306
Net income attributable to noncontrolling interests	25	54	26	71
Net Income (Loss)	86	92	316	235
SOUTHERN POWER CO | Wholesale electric revenues
Operating Revenues:
Total operating revenues	455	496	1,197	1,363
SOUTHERN POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Total operating revenues	116	134	320	326
SOUTHERN POWER CO | Other
Operating Revenues:
Total operating revenues	3	5	10	10
SOUTHERN POWER CO | Fuel
Operating Expenses:
Total cost of natural gas	166	190	449	511
SOUTHERN POWER CO | Purchased power
Operating Expenses:
Total cost of natural gas	26	37	82	137
SOUTHERN Co GAS
Operating Revenues:
Total operating revenues	498	492	2,661	2,861
Operating Expenses:
Other operations and maintenance	208	216	642	730
Depreciation and amortization	121	119	359	374
Taxes other than income taxes	33	32	161	157
Impairment charges	92	0	92	42
(Gain) loss on dispositions, net	0	(353)	0	(317)
Total operating expenses	533	118	2,210	2,051
Operating Income (Loss)	(35)	374	451	810
Other Income and (Expense):
Earnings from equity method investments	35	34	115	108
Interest expense, net of amounts capitalized	(56)	(52)	(174)	(170)
Other income (expense), net	5	6	16	21
Total other income and (expense)	(16)	(12)	(43)	(41)
Earnings (Loss) Before Income Taxes	(51)	362	408	769
Income taxes	(22)	316	61	475
Consolidated Net Income	(29)	46	347	294
Net Income (Loss)	(29)	46	347	294
SOUTHERN Co GAS | Natural gas
Operating Revenues:
Total operating revenues	498	487	2,661	2,829
Operating Expenses:
Total cost of natural gas	79	104	956	1,053
SOUTHERN Co GAS | Other
Operating Revenues:
Total operating revenues	0	0	0	55
Operating Expenses:
Total cost of natural gas	0	0	0	12
SOUTHERN Co GAS | Alternative revenue programs
Operating Revenues:
Total operating revenues	$ 0	$ 5	$ 0	$ (23)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating revenues	$ 5,995	$ 6,159	$ 16,505	$ 18,158
Alternative revenue programs
Operating revenues	0	5	0	(23)
SOUTHERN Co GAS
Operating revenues	498	492	2,661	2,861
Excise taxes collected	10	9	88	83
SOUTHERN Co GAS | Alternative revenue programs
Operating revenues	$ 0	$ 5	$ 0	$ (23)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 1,345	$ 1,222	$ 4,335	$ 2,031
Qualifying hedges:
Changes in fair value, net of tax	(92)	(11)	(152)	(19)
Reclassification adjustment for amounts included in net income, net of tax	50	14	74	60
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	1	8	2	11
Total other comprehensive income (loss)	(41)	11	(76)	52
Comprehensive Income (Loss)	1,304	1,233	4,259	2,083
Dividends on preferred stock of subsidiaries	4	4	11	12
Comprehensive income attributable to noncontrolling interests	25	54	26	71
Comprehensive Income (Loss) Attributable to Parent	1,275	1,175	4,222	2,000
ALABAMA POWER CO
Net income	473	377	993	868
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax	1	1	3	3
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	1	1	3	3
Comprehensive Income (Loss)	474	378	996	871
Dividends on preferred stock of subsidiaries	4	4	11	11
GEORGIA POWER CO
Net income	839	664	1,598	621
Qualifying hedges:
Changes in fair value, net of tax	(35)	0	(62)	0
Reclassification adjustment for amounts included in net income, net of tax	0	1	1	3
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	(35)	1	(61)	3
Comprehensive Income (Loss)	804	665	1,537	624
MISSISSIPPI POWER CO
Net income	65	47	139	87
Qualifying hedges:
Changes in fair value, net of tax	0	0	0	(1)
Reclassification adjustment for amounts included in net income, net of tax	0	0	1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	0	0	1	0
Comprehensive Income (Loss)	65	47	140	87
Dividends on preferred stock of subsidiaries	0	0	0	1
SOUTHERN POWER CO
Net income	111	146	342	306
Qualifying hedges:
Changes in fair value, net of tax	(53)	(11)	(84)	(19)
Reclassification adjustment for amounts included in net income, net of tax	45	11	64	46
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0	0	0	1
Total other comprehensive income (loss)	(8)	0	(20)	28
Comprehensive Income (Loss)	103	146	322	334
Comprehensive income attributable to noncontrolling interests	25	54	26	71
Comprehensive Income (Loss) Attributable to Parent	78	92	296	263
SOUTHERN Co GAS
Net income	(29)	46	347	294
Qualifying hedges:
Changes in fair value, net of tax	(3)	0	(6)	2
Reclassification adjustment for amounts included in net income, net of tax	0	0	0	2
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0	6	(1)	5
Total other comprehensive income (loss)	(3)	6	(7)	9
Comprehensive Income (Loss)	$ (32)	$ 52	$ 340	$ 303

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Qualifying hedges:
Changes in fair value, tax	$ (33)	$ (4)	$ (54)	$ (6)
Reclassification adjustment for amounts included in net income, tax	17	5	25	21
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	0	3	0	4
ALABAMA POWER CO
Qualifying hedges:
Reclassification adjustment for amounts included in net income, tax	0	0	1	1
GEORGIA POWER CO
Qualifying hedges:
Changes in fair value, tax	(12)	0	(21)	0
Reclassification adjustment for amounts included in net income, tax	0	0	0	1
MISSISSIPPI POWER CO
Qualifying hedges:
Changes in fair value, tax	0	0	0	(1)
Reclassification adjustment for amounts included in net income, tax	0	0	0	0
SOUTHERN POWER CO
Qualifying hedges:
Changes in fair value, tax	(18)	(4)	(28)	(7)
Reclassification adjustment for amounts included in net income, tax	15	4	21	16
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	0	0	0	0
SOUTHERN Co GAS
Qualifying hedges:
Changes in fair value, tax	(3)	0	(4)	1
Reclassification adjustment for amounts included in net income, tax	0	0	0	1
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, tax	$ 0	$ 2	$ (1)	$ 2

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating Activities:
Net income	$ 4,335	$ 2,031
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	2,514	2,647
Deferred income taxes	253	(286)
Utilization of federal investment tax credits	722	0
Allowance for equity funds used during construction	(96)	(99)
Pension, postretirement, and other employee benefits	(114)	(60)
Settlement of asset retirement obligations	(225)	(160)
Stock based compensation expense	87	108
Estimated loss on plants	12	1,081
Asset impairment	142	197
(Gain) loss on dispositions, net	(2,517)	(324)
Other, net	1	(20)
Changes in certain current assets and liabilities —
-Receivables	588	37
-Prepayments	61	14
-Natural gas for sale	49	87
-Other current assets	(110)	(90)
-Accounts payable	(1,155)	(248)
-Accrued taxes	679	839
-Accrued compensation	(191)	(138)
-Other current liabilities	(154)	(32)
Net cash provided from operating activities	4,881	5,584
Investing Activities:
Property additions	(5,417)	(5,793)
Nuclear decommissioning trust fund purchases	(683)	(846)
Nuclear decommissioning trust fund sales	678	840
Proceeds from dispositions and asset sales	5,036	2,773
Cost of removal, net of salvage	(290)	(252)
Change in construction payables, net	(132)	91
Investment in unconsolidated subsidiaries	(141)	(93)
Payments pursuant to LTSAs	(139)	(157)
Other investing activities	15	(63)
Net cash used for investing activities	(1,073)	(3,500)
Financing Activities:
Increase (decrease) in notes payable, net	(773)	(1,225)
Proceeds —
Long-term debt	4,737	1,950
Common stock	623	878
Short-term borrowings	250	3,150
Redemptions and repurchases —
Long-term debt	(3,216)	(4,498)
Short-term borrowings	(1,850)	(1,800)
Distributions to noncontrolling interests	(125)	(86)
Capital contributions from noncontrolling interests	11	1,333
Payment of common stock dividends	(1,919)	(1,805)
Other financing activities	(130)	(237)
Net cash used for financing activities	(2,392)	(2,340)
Net Change in Cash, Cash Equivalents, and Restricted Cash	1,416	(256)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1,519	2,147
Cash, Cash Equivalents, and Restricted Cash at End of Period	2,935	1,891
Cash paid during the period for —
Interest, net of amounts capitalized	1,318	1,402
Income taxes, net	265	137
Noncash transactions — Accrued property additions at end of period	953	1,125
ALABAMA POWER CO
Operating Activities:
Net income	993	868
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	756	683
Deferred income taxes	148	104
Allowance for equity funds used during construction	(41)	(43)
Pension, postretirement, and other employee benefits	(30)	(17)
Settlement of asset retirement obligations	(76)	(31)
Other, net	17	11
Changes in certain current assets and liabilities —
-Receivables	(115)	(207)
-Prepayments	(30)	(26)
-Other current assets	(30)	66
-Accounts payable	(267)	(194)
-Accrued taxes	149	225
-Accrued compensation	(55)	(41)
-Other current liabilities	41	60
-Materials and supplies	11	(69)
Net cash provided from operating activities	1,471	1,389
Investing Activities:
Property additions	(1,239)	(1,529)
Nuclear decommissioning trust fund purchases	(201)	(207)
Nuclear decommissioning trust fund sales	201	207
Cost of removal, net of salvage	(79)	(78)
Change in construction payables, net	(99)	30
Other investing activities	(22)	(23)
Net cash used for investing activities	(1,439)	(1,600)
Proceeds —
Senior notes	600	500
Capital contributions from parent company	1,252	495
Redemptions and repurchases —
Senior notes	(200)	0
Payment of common stock dividends	(633)	(602)
Other financing activities	(27)	(24)
Net cash used for financing activities	992	369
Net Change in Cash, Cash Equivalents, and Restricted Cash	1,024	158
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	313	544
Cash, Cash Equivalents, and Restricted Cash at End of Period	1,337	702
Cash paid during the period for —
Interest, net of amounts capitalized	246	220
Income taxes, net	89	30
Noncash transactions — Accrued property additions at end of period	173	275
GEORGIA POWER CO
Operating Activities:
Net income	1,598	621
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	887	854
Deferred income taxes	145	(185)
Allowance for equity funds used during construction	(49)	(50)
Pension, postretirement, and other employee benefits	(85)	(46)
Settlement of asset retirement obligations	(110)	(82)
Estimated loss on plants	0	1,060
Other, net	61	9
Changes in certain current assets and liabilities —
-Receivables	(128)	(205)
-Other current assets	(35)	(36)
-Accounts payable	(134)	109
-Accrued taxes	138	26
-Accrued compensation	(12)	(32)
-Other current liabilities	0	(111)
-Fossil fuel stock	(13)	70
-Prepaid income taxes	102	231
Net cash provided from operating activities	2,365	2,233
Investing Activities:
Property additions	(2,581)	(2,276)
Nuclear decommissioning trust fund purchases	(483)	(638)
Nuclear decommissioning trust fund sales	477	633
Proceeds from dispositions and asset sales	9	138
Cost of removal, net of salvage	(136)	(71)
Payments pursuant to LTSAs	(17)	(52)
Other investing activities	13	(19)
Change in construction payables, net of joint owner portion	(75)	72
Net cash used for investing activities	(2,793)	(2,213)
Financing Activities:
Increase (decrease) in notes payable, net	(294)	102
Proceeds —
Short-term borrowings	250	0
Senior notes	750	0
Capital contributions from parent company	82	2,335
FFB loan	835	0
Pollution control revenue bonds	584	0
Redemptions and repurchases —
Short-term borrowings	0	(150)
Senior notes	0	(1,000)
Pollution control revenue bonds	(223)	(469)
Other long-term debt	0	(100)
Payment of common stock dividends	(1,182)	(1,043)
Other financing activities	(37)	(15)
Premiums on redemption and repurchases of senior notes	0	(152)
Net cash used for financing activities	765	(492)
Net Change in Cash, Cash Equivalents, and Restricted Cash	337	(472)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	112	852
Cash, Cash Equivalents, and Restricted Cash at End of Period	449	380
Cash paid during the period for —
Interest, net of amounts capitalized	296	315
Income taxes, net	45	141
Noncash transactions — Accrued property additions at end of period	589	670
MISSISSIPPI POWER CO
Operating Activities:
Net income	139	87
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	148	129
Deferred income taxes	10	420
Settlement of asset retirement obligations	(28)	(22)
Estimated loss on plants	12	21
Other, net	(4)	27
Changes in certain current assets and liabilities —
-Receivables	(11)	(46)
-Other current assets	18	(6)
-Accounts payable	(26)	(3)
-Accrued taxes	(12)	57
-Accrued compensation	(10)	(9)
-Other current liabilities	6	1
Net cash provided from operating activities	242	656
Investing Activities:
Property additions	(134)	(117)
Change in construction payables, net	(16)	(9)
Payments pursuant to LTSAs	(18)	(28)
Other investing activities	(30)	(16)
Net cash used for investing activities	(198)	(170)
Financing Activities:
Increase (decrease) in notes payable, net	0	(4)
Proceeds —
Short-term borrowings	0	300
Senior notes	0	600
Pollution control revenue bonds	43	0
Redemptions and repurchases —
Short-term borrowings	0	(300)
Pollution control revenue bonds	0	(43)
Other long-term debt	0	(900)
Other financing activities	1	(8)
Return of capital	(113)	0
Net cash used for financing activities	(69)	(355)
Net Change in Cash, Cash Equivalents, and Restricted Cash	(25)	131
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	293	248
Cash, Cash Equivalents, and Restricted Cash at End of Period	268	379
Cash paid during the period for —
Interest, net of amounts capitalized	55	57
Income taxes, net	0	(483)
Noncash transactions — Accrued property additions at end of period	20	23
SOUTHERN POWER CO
Operating Activities:
Net income	342	306
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	377	394
Deferred income taxes	(122)	(337)
Utilization of federal investment tax credits	705	0
Asset impairment	0	155
Other, net	(43)	(2)
Amortization of investment tax credits	(136)	(43)
Changes in certain current assets and liabilities —
-Receivables	15	(41)
-Other current assets	(3)	1
-Accounts payable	(5)	(27)
-Accrued taxes	66	256
-Other current liabilities	(8)	(1)
-Prepaid income taxes	33	5
Net cash provided from operating activities	1,221	666
Investing Activities:
Business acquisitions, net of cash acquired	(50)	(64)
Property additions	(284)	(226)
Proceeds from dispositions and asset sales	572	0
Change in construction payables, net	(11)	3
Investment in unconsolidated subsidiaries	(116)	0
Payments pursuant to LTSAs	(85)	(57)
Other investing activities	10	20
Net cash used for investing activities	36	(324)
Financing Activities:
Increase (decrease) in notes payable, net	0	(68)
Proceeds —
Short-term borrowings	0	200
Capital contributions from parent company	59	0
Redemptions and repurchases —
Short-term borrowings	(100)	0
Senior notes	0	(350)
Other long-term debt	0	(420)
Distributions to noncontrolling interests	(125)	(86)
Capital contributions from noncontrolling interests	11	1,333
Payment of common stock dividends	(154)	(234)
Other financing activities	(6)	(15)
Return of capital	(755)	(650)
Net cash used for financing activities	(1,070)	(290)
Net Change in Cash, Cash Equivalents, and Restricted Cash	187	52
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	181	140
Cash, Cash Equivalents, and Restricted Cash at End of Period	368	192
Cash paid during the period for —
Interest, net of amounts capitalized	133	138
Income taxes, net	(612)	(102)
Noncash transactions — Accrued property additions at end of period	41	37
SOUTHERN Co GAS
Operating Activities:
Net income	347	294
Adjustments to reconcile net income to net cash provided from operating activities —
Depreciation and amortization, total	359	374
Deferred income taxes	96	(83)
Mark-to-market adjustments	44	23
Asset impairment	92	42
(Gain) loss on dispositions, net	0	(317)
Other, net	(58)	(41)
Changes in certain current assets and liabilities —
-Receivables	832	445
-Natural gas for sale	49	87
-Other current assets	45	(2)
-Accounts payable	(607)	(59)
-Accrued taxes	(68)	(64)
-Accrued compensation	(34)	2
-Other current liabilities	(48)	35
Net cash provided from operating activities	1,049	736
Investing Activities:
Property additions	(1,008)	(1,029)
Proceeds from dispositions and asset sales	32	2,631
Cost of removal, net of salvage	(59)	(67)
Change in construction payables, net	57	(14)
Investment in unconsolidated subsidiaries	(25)	(90)
Other investing activities	14	18
Net cash used for investing activities	(989)	1,449
Financing Activities:
Increase (decrease) in notes payable, net	(383)	(1,382)
Proceeds —
Capital contributions from parent company	820	35
First mortgage bonds	200	100
Redemptions and repurchases —
Long-term debt	0	(200)
Senior notes	(300)	0
First mortgage bonds	(50)	0
Payment of common stock dividends	(353)	(351)
Other financing activities	(2)	(3)
Return of capital	0	(400)
Net cash used for financing activities	(68)	(2,201)
Net Change in Cash, Cash Equivalents, and Restricted Cash	(8)	(16)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	70	78
Cash, Cash Equivalents, and Restricted Cash at End of Period	62	62
Cash paid during the period for —
Interest, net of amounts capitalized	180	175
Income taxes, net	48	682
Noncash transactions — Accrued property additions at end of period	$ 154	$ 121

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Interest capitalized	$ 55	$ 53
ALABAMA POWER CO
Interest capitalized	15	15
GEORGIA POWER CO
Interest capitalized	25	19
MISSISSIPPI POWER CO
Interest received	1	0
SOUTHERN POWER CO
Interest capitalized	11	14
SOUTHERN Co GAS
Interest capitalized	$ 5	$ 5

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 2,931	$ 1,396
Receivables —
Customer accounts receivable	1,812	1,726
Energy marketing receivables	336	801
Unbilled revenues	591	654
Under recovered fuel clause revenues	0	115
Other accounts and notes receivable	693	813
Accumulated provision for uncollectible accounts	(47)	(50)
Materials and supplies	1,412	1,465
Fossil fuel for generation	437	405
Natural gas for sale	475	524
Prepaid expenses	279	432
Assets from risk management activities, net of collateral	116	222
Other regulatory assets	657	525
Assets held for sale	17	393
Other current assets	208	162
Total current assets	9,917	9,583
Property, Plant, and Equipment:
In service	103,529	103,706
Less: Accumulated depreciation	30,469	31,038
Plant in service, net of depreciation	73,060	72,668
Nuclear fuel, at amortized cost	849	875
Construction work in progress	7,804	7,254
Total property, plant, and equipment	81,713	80,797
Other Property and Investments:
Goodwill	5,280	5,315
Equity investments in unconsolidated subsidiaries	1,540	1,580
Other intangible assets, net of amortization	550	613
Nuclear decommissioning trusts, at fair value	1,965	1,721
Leveraged leases	799	798
Miscellaneous property and investments	394	269
Total other property and investments	10,528	10,296
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,818
Deferred charges related to income taxes	796	794
Unamortized loss on reacquired debt	307	323
Regulatory assets – asset retirement obligations	4,436	2,933
Other regulatory assets, deferred	6,289	5,375
Assets held for sale, deferred	631	5,350
Other deferred charges and assets	1,156	1,463
Total deferred charges and other assets	15,433	16,238
Total Assets	117,591	116,914
Current Liabilities:
Securities due within one year	3,313	3,198
Notes payable	542	2,915
Energy marketing trade payables	368	856
Accounts payable —
Accounts payable	1,898	2,580
Customer deposits	494	522
Accrued taxes —
Accrued income taxes	179	21
Other accrued taxes	689	635
Accrued interest	386	472
Accrued compensation	798	1,030
Asset retirement obligations	433	404
Other regulatory liabilities	318	376
Liabilities held for sale	6	425
Operating lease obligations	229
Other current liabilities	881	852
Total current liabilities	10,534	14,286
Long-term Debt	42,098	40,736
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	7,737	6,558
Deferred credits related to income taxes	6,356	6,460
Accumulated deferred ITCs	2,306	2,372
Employee benefit obligations	1,999	2,147
Operating lease obligations, deferred	1,601
Asset retirement obligations, deferred	9,527	8,990
Accrued environmental remediation	241	268
Other cost of removal obligations	2,263	2,297
Other regulatory liabilities, deferred	265	169
Liabilities held for sale, deferred	20	2,836
Other deferred credits and liabilities	562	465
Total deferred credits and other liabilities	32,877	32,562
Total Liabilities	85,509	87,584
Redeemable Preferred Stock of Subsidiaries	291	291
Total stockholders' equity	31,791	29,039
Total Liabilities and Stockholders' Equity	117,591	116,914
ALABAMA POWER CO
Current Assets:
Cash and cash equivalents	1,337	313
Receivables —
Customer accounts receivable	501	403
Unbilled revenues	172	150
Other accounts and notes receivable	70	51
Accumulated provision for uncollectible accounts	(21)	(10)
Affiliated	48	94
Materials and supplies	524	546
Fossil fuel for generation	163	141
Prepaid expenses	64	66
Other regulatory assets	204	137
Other current assets	24	18
Total current assets	3,086	1,909
Property, Plant, and Equipment:
In service	29,648	30,402
Less: Accumulated depreciation	9,465	9,988
Plant in service, net of depreciation	20,183	20,414
Nuclear fuel, at amortized cost	304	324
Construction work in progress	827	1,113
Total property, plant, and equipment	21,314	21,851
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	64	65
Nuclear decommissioning trusts, at fair value	975	847
Miscellaneous property and investments	127	127
Total other property and investments	1,166	1,039
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	143
Deferred charges related to income taxes	241	240
Regulatory assets – asset retirement obligations	1,047	147
Other regulatory assets, deferred	1,788	1,240
Other deferred charges and assets	189	188
Deferred under recovered regulatory clause revenues	45	116
Total deferred charges and other assets	3,453	1,931
Total Assets	29,019	26,730
Current Liabilities:
Securities due within one year	1	201
Accounts payable —
Affiliated	351	364
Other	317	614
Customer deposits	99	96
Accrued taxes —
Other accrued taxes	167	44
Accrued interest	74	89
Accrued compensation	171	227
Asset retirement obligations	153	163
Operating lease obligations	49
Other current liabilities	122	161
Total current liabilities	1,455	1,959
Long-term Debt	8,520	7,923
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,134	2,962
Deferred credits related to income taxes	2,001	2,027
Accumulated deferred ITCs	102	106
Employee benefit obligations	296	314
Operating lease obligations, deferred	109
Asset retirement obligations, deferred	3,400	3,047
Other cost of removal obligations	441	497
Other regulatory liabilities, deferred	151	69
Other deferred credits and liabilities	33	58
Total deferred credits and other liabilities	9,667	9,080
Total Liabilities	19,642	18,962
Redeemable Preferred Stock	291	291
Total stockholders' equity	9,086	7,477
Total Liabilities and Stockholders' Equity	29,019	26,730
GEORGIA POWER CO
Current Assets:
Cash and cash equivalents	449	4
Restricted cash and cash equivalents	0	108
Receivables —
Customer accounts receivable	767	591
Unbilled revenues	282	208
Under recovered fuel clause revenues	0	115
Other accounts and notes receivable	205	80
Accumulated provision for uncollectible accounts	(2)	(2)
Affiliated	28	39
Joint owner accounts receivable	152	170
Materials and supplies	499	519
Fossil fuel for generation	244	231
Prepaid expenses	15	142
Other regulatory assets	270	199
Other current assets	101	70
Total current assets	3,010	2,474
Property, Plant, and Equipment:
In service	37,409	37,675
Less: Accumulated depreciation	11,670	12,096
Plant in service, net of depreciation	25,739	25,579
Nuclear fuel, at amortized cost	544	550
Construction work in progress	5,690	4,833
Total property, plant, and equipment	31,973	30,962
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	51	51
Nuclear decommissioning trusts, at fair value	990	873
Miscellaneous property and investments	68	72
Total other property and investments	1,109	996
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	1,461
Deferred charges related to income taxes	520	517
Regulatory assets – asset retirement obligations	3,181	2,644
Other regulatory assets, deferred	2,763	2,258
Other deferred charges and assets	398	514
Total deferred charges and other assets	8,323	5,933
Total Assets	44,415	40,365
Current Liabilities:
Securities due within one year	1,504	617
Notes payable	250	294
Accounts payable —
Affiliated	540	575
Other	756	890
Customer deposits	282	276
Accrued taxes —
Other accrued taxes	498	377
Accrued interest	98	105
Accrued compensation	192	221
Asset retirement obligations	259	202
Other regulatory liabilities	183	169
Operating lease obligations	143	0
Other current liabilities	234	183
Total current liabilities	4,939	3,909
Long-term Debt	10,440	9,364
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	3,216	3,062
Deferred credits related to income taxes	3,079	3,080
Accumulated deferred ITCs	257	262
Employee benefit obligations	525	599
Operating lease obligations, deferred	1,287
Asset retirement obligations, deferred	5,680	5,627
Other deferred credits and liabilities	228	139
Total deferred credits and other liabilities	14,272	12,769
Total Liabilities	29,651	26,042
Total stockholders' equity	14,764	14,323
Total Liabilities and Stockholders' Equity	44,415	40,365
MISSISSIPPI POWER CO
Current Assets:
Cash and cash equivalents	268	293
Receivables —
Customer accounts receivable	45	34
Unbilled revenues	44	41
Other accounts and notes receivable	27	31
Affiliated	23	21
Materials and supplies	54	53
Fossil fuel for generation	18	20
Other regulatory assets	102	116
Other current assets	9	19
Total current assets	590	628
Property, Plant, and Equipment:
In service	4,829	4,900
Less: Accumulated depreciation	1,450	1,429
Plant in service, net of depreciation	3,379	3,471
Construction work in progress	109	103
Total property, plant, and equipment	3,488	3,574
Other Property and Investments:
Total other property and investments	136	24
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	7
Deferred charges related to income taxes	32	33
Regulatory assets – asset retirement obligations	208	143
Other regulatory assets, deferred	324	332
Other deferred charges and assets	27	2
Accumulated deferred income taxes	141	150
Total deferred charges and other assets	732	660
Total Assets	4,946	4,886
Current Liabilities:
Securities due within one year	300	40
Accounts payable —
Affiliated	63	60
Other	44	90
Accrued taxes —
Other accrued taxes	82	95
Accrued interest	14	15
Accrued compensation	28	38
Asset retirement obligations	17	34
Other regulatory liabilities	21	12
Operating lease obligations	2
Other current liabilities	52	28
Accrued plant closure costs	21	29
Over recovered regulatory clause liabilities	21	14
Total current liabilities	663	455
Long-term Debt	1,316	1,539
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	392	378
Deferred credits related to income taxes	357	382
Employee benefit obligations	108	115
Operating lease obligations, deferred	5
Asset retirement obligations, deferred	178	126
Other cost of removal obligations	189	185
Other regulatory liabilities, deferred	79	81
Other deferred credits and liabilities	25	16
Total deferred credits and other liabilities	1,328	1,283
Total Liabilities	3,307	3,277
Total stockholders' equity	1,639	1,609
Total Liabilities and Stockholders' Equity	4,946	4,886
SOUTHERN POWER CO
Current Assets:
Cash and cash equivalents	368	181
Receivables —
Customer accounts receivable	152	111
Other accounts and notes receivable	41	116
Affiliated	49	55
Materials and supplies	190	220
Other current assets	38	37
Prepaid income taxes	296	25
Total current assets	1,134	745
Property, Plant, and Equipment:
In service	13,072	13,271
Less: Accumulated depreciation	2,374	2,171
Plant in service, net of depreciation	10,698	11,100
Construction work in progress	541	430
Total property, plant, and equipment	11,239	11,530
Other Property and Investments:
Miscellaneous property and investments	28	0
Intangible assets, net of amortization	326	345
Total other property and investments	354	345
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	368
Assets held for sale, deferred	600	576
Other deferred charges and assets	207	373
Prepaid LTSAs	145	98
Accumulated deferred income taxes	318	1,186
Income taxes receivable, non-current	32	30
Total deferred charges and other assets	1,670	2,263
Total Assets	14,397	14,883
Current Liabilities:
Securities due within one year	900	599
Notes payable	0	100
Accounts payable —
Affiliated	79	92
Other	74	77
Accrued taxes —
Other accrued taxes	21	6
Accrued interest	31	36
Operating lease obligations	22
Other current liabilities	133	121
Total current liabilities	1,238	1,031
Long-term Debt	4,060	4,418
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	117	105
Accumulated deferred ITCs	1,745	1,832
Operating lease obligations, deferred	373
Other deferred credits and liabilities	171	213
Total deferred credits and other liabilities	2,406	2,150
Total Liabilities	7,704	7,599
Total stockholders' equity	6,693	7,284
Total Liabilities and Stockholders' Equity	14,397	14,883
SOUTHERN Co GAS
Current Assets:
Cash and cash equivalents	59	64
Receivables —
Customer accounts receivable	186	370
Energy marketing receivables	336	801
Unbilled revenues	55	213
Other accounts and notes receivable	103	142
Accumulated provision for uncollectible accounts	(18)	(30)
Affiliated	12	11
Natural gas for sale	475	524
Prepaid expenses	86	118
Assets from risk management activities, net of collateral	112	219
Other regulatory assets	82	73
Other current assets	43	50
Total current assets	1,531	2,555
Property, Plant, and Equipment:
In service	16,058	15,177
Less: Accumulated depreciation	4,590	4,400
Plant in service, net of depreciation	11,468	10,777
Construction work in progress	546	580
Total property, plant, and equipment	12,014	11,357
Other Property and Investments:
Goodwill	5,015	5,015
Equity investments in unconsolidated subsidiaries	1,487	1,538
Other intangible assets, net of amortization	78	101
Miscellaneous property and investments	20	20
Total other property and investments	6,600	6,674
Deferred Charges and Other Assets:
Operating lease right-of-use assets, net of amortization	92
Other regulatory assets, deferred	621	669
Other deferred charges and assets	189	193
Total deferred charges and other assets	902	862
Total Assets	21,047	21,448
Current Liabilities:
Securities due within one year	0	357
Notes payable	267	650
Energy marketing trade payables	368	856
Accounts payable —
Affiliated	42	45
Other	334	402
Customer deposits	96	133
Accrued taxes —
Accrued income taxes	0	66
Other accrued taxes	72	75
Accrued interest	63	55
Accrued compensation	64	100
Other regulatory liabilities	100	79
Operating lease obligations	14
Other current liabilities	127	130
Liabilities from risk management activities, net of collateral	50	76
Total current liabilities	1,583	3,024
Long-term Debt	5,755	5,583
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	1,108	1,016
Deferred credits related to income taxes	890	940
Employee benefit obligations	353	357
Operating lease obligations, deferred	77
Accrued environmental remediation	241	268
Other cost of removal obligations	1,601	1,585
Other deferred credits and liabilities	46	105
Total deferred credits and other liabilities	4,316	4,271
Total Liabilities	11,654	12,878
Total stockholders' equity	9,393	8,570
Total Liabilities and Stockholders' Equity	$ 21,047	$ 21,448

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other intangible assets, amortization	$ 265	$ 235
SOUTHERN POWER CO
Other intangible assets, amortization	64	61
SOUTHERN Co GAS
Other intangible assets, amortization	$ 168	$ 145

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, 2017			1,009	1						31					9					1
Beginning balance at Dec. 31, 2017		$ 25,528	$ 5,038	$ (36)	$ 10,469	$ 8,885	$ (189)	$ 1,361	$ 6,829	$ 1,222	$ 2,986	$ 2,647	$ (26)	$ 11,931	$ 398	$ 7,328	$ 4,215	$ (10)	$ 1,358	$ 38	$ 4,529	$ (3,205)	$ (4)	$ 6,498	$ 3,662	$ 1,478	$ (2)	$ 5,138	$ 1,360	$ 9,022	$ 9,214	$ (212)	$ 20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		938				938			225			225		352			352		(7)			(7)		121		121		121		279		279
Other comprehensive income (loss)		30					30		1				1	1				1	(1)				(1)	24			24	24		2			2
Stock issued (in shares)			4
Stock issued		113	$ 16		97
Stock-based compensation		36			36
Cash dividends on common stock		(586)				(586)			(202)			(202)		(339)			(339)							(78)		(78)		(78)		(118)		(118)
Contributions from noncontrolling interests		9						9																9					9
Distributions to noncontrolling interests		(13)						(13)																(13)					(13)
Net income (loss) attributable to noncontrolling interests		(6)						(6)																(6)					(6)
Other		(24)		$ (2)	1	20	(41)	(2)	(6)				(6)	(1)		1		(2)	(1)			(1)		2		(2)	5	3	(1)	0		(4)	4
Capital contributions from parent company									488		488			1,476		1,476			2		2			1	1			1		14	14
Ending balance (in shares) at Mar. 31, 2018			1,013	1						31					9					1
Ending balance at Mar. 31, 2018		26,025	$ 5,054	$ (38)	10,603	9,257	(200)	1,349	7,335	$ 1,222	3,474	2,670	(31)	13,420	$ 398	8,805	4,228	(11)	1,351	$ 38	4,531	(3,213)	(5)	6,558	3,663	1,519	27	5,209	1,349	9,199	9,228	(55)	26
Beginning balance (in shares) at Dec. 31, 2017			1,009	1						31					9					1
Beginning balance at Dec. 31, 2017		25,528	$ 5,038	$ (36)	10,469	8,885	(189)	1,361	6,829	$ 1,222	2,986	2,647	(26)	11,931	$ 398	7,328	4,215	(10)	1,358	$ 38	4,529	(3,205)	(4)	6,498	3,662	1,478	(2)	5,138	1,360	9,022	9,214	(212)	20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		1,948							857										86					235						294
Ending balance (in shares) at Sep. 30, 2018			1,030	1						31					9					1
Ending balance at Sep. 30, 2018		28,065	$ 5,140	$ (39)	10,905	9,048	(177)	3,188	7,585	$ 1,222	3,490	2,902	(29)	13,851	$ 398	9,670	3,792	(9)	1,443	$ 38	4,529	(3,119)	(5)	7,301	2,604	1,478	31	4,113	3,188	8,623	8,863	(273)	33
Beginning balance (in shares) at Mar. 31, 2018			1,013	1						31					9					1
Beginning balance at Mar. 31, 2018		26,025	$ 5,054	$ (38)	10,603	9,257	(200)	1,349	7,335	$ 1,222	3,474	2,670	(31)	13,420	$ 398	8,805	4,228	(11)	1,351	$ 38	4,531	(3,213)	(5)	6,558	3,663	1,519	27	5,209	1,349	9,199	9,228	(55)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(154)				(154)			259			259		(396)			(396)		46			46		22		22		22		(31)		(31)
Other comprehensive income (loss)		12					12		1				1	1				1						4			4	4		1			1
Stock issued (in shares)			2
Stock issued		109	$ 12		97
Stock-based compensation		12			12
Cash dividends on common stock		(607)				(607)			(200)			(200)		(352)			(352)							(78)		(78)		(78)		(117)		(117)
Contributions from noncontrolling interests		22						22																22					22
Distributions to noncontrolling interests		(29)						(29)																(29)					(29)
Net income (loss) attributable to noncontrolling interests		23						23																23					23
Other		(4)		$ (1)	(2)	(2)		1	1		1								1			1		2		1		1	1	1		1
Sale of noncontrolling interests		1,283			(407)			1,690																1,283	(407)			(407)	1,690
Capital contributions from parent company									5		5			29		29								17	17			17		8	8
Return of capital to parent company																								(250)	(250)			(250)
Ending balance (in shares) at Jun. 30, 2018			1,015	1						31					9					1
Ending balance at Jun. 30, 2018		26,692	$ 5,066	$ (39)	10,303	8,494	(188)	3,056	7,401	$ 1,222	3,480	2,729	(30)	12,702	$ 398	8,834	3,480	(10)	1,398	$ 38	4,531	(3,166)	(5)	7,574	3,023	1,464	31	4,518	3,056	9,061	9,236	(202)	27
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		1,164				1,164			373			373		664			664		47			47		92		92		92		46		46
Other comprehensive income (loss)		11					11		1				1	1				1												6			6
Stock issued (in shares)			15
Stock issued		656	$ 74		582
Stock-based compensation		26			26
Cash dividends on common stock		(610)				(610)			(200)			(200)		(352)			(352)							(78)		(78)		(78)		(116)		(116)
Contributions from noncontrolling interests		123						123																123					123
Distributions to noncontrolling interests		(45)						(45)																(45)					(45)
Net income (loss) attributable to noncontrolling interests		54						54																54					54
Other		(2)			(2)																									(1)		(1)
Sale of noncontrolling interests		(4)			(4)																			(4)	(4)			(4)
Capital contributions from parent company									10		10			836		836														27	27
Return of capital to parent company																			(2)		(2)			(415)	(415)			(415)		(400)	(400)
Ending balance (in shares) at Sep. 30, 2018			1,030	1						31					9					1
Ending balance at Sep. 30, 2018		28,065	$ 5,140	$ (39)	10,905	9,048	(177)	3,188	7,585	$ 1,222	3,490	2,902	(29)	13,851	$ 398	9,670	3,792	(9)	1,443	$ 38	4,529	(3,119)	(5)	7,301	2,604	1,478	31	4,113	3,188	8,623	8,863	(273)	33
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
Other comprehensive income (loss)									1				1	1				1						(4)			(4)	(4)		(1)			(1)
Stock issued (in shares)			6
Stock issued		224	$ 28		196
Stock-based compensation		24			24
Cash dividends on common stock		(623)				(623)			(211)			(211)		(394)			(394)							(51)		(51)		(51)		(118)		(118)
Contributions from noncontrolling interests		3						3																3					3
Distributions to noncontrolling interests		(41)						(41)																(41)					(41)
Net income (loss) attributable to noncontrolling interests		(29)						(29)																(29)					(29)
Other		6		$ (2)	7			1						(1)		(1)								(1)	(1)	(1)		(2)	1
Capital contributions from parent company									1,236		1,236			29		29			2		2			1	1			1		17	17
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, 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)		4,298							982										139					316						347
Ending balance (in shares) at Sep. 30, 2019			1,050	1						31					9					1
Ending balance at Sep. 30, 2019		31,791	$ 5,234	$ (41)	11,512	11,087	(279)	4,278	9,086	$ 1,222	4,765	3,124	(25)	14,764	$ 398	10,408	4,028	(70)	1,639	$ 38	4,437	(2,832)	(4)	6,693	905	1,514	(4)	2,415	4,278	9,393	9,692	(318)	19
Beginning balance (in shares) at Mar. 31, 2019			1,041	1						31					9					1
Beginning balance at Mar. 31, 2019		30,687	$ 5,192	$ (40)	11,321	10,167	(203)	4,250	8,720	$ 1,222	4,744	2,781	(27)	14,269	$ 398	10,350	3,529	(8)	1,610	$ 38	4,510	(2,934)	(4)	7,218	1,600	1,356	12	2,968	4,250	8,738	8,873	(160)	25
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		899				899			296			296		448			448		37			37		174		174		174		106		106
Other comprehensive income (loss)		(35)					(35)		1				1	(27)				(27)						(8)			(8)	(8)		(3)			(3)
Stock issued (in shares)			5
Stock issued		228	$ 25		203
Stock-based compensation		11			11
Cash dividends on common stock		(646)				(646)			(211)			(211)		(394)			(394)							(52)		(52)		(52)		(117)		(117)
Contributions from noncontrolling interests		2						2																2					2
Distributions to noncontrolling interests		(47)						(47)																(47)					(47)
Net income (loss) attributable to noncontrolling interests		29						29																29					29
Other		3		$ (1)	5			(1)						0		1	(1)							0		1		1	(1)
Capital contributions from parent company									23		23			20		20			8		8			7	7			7		35	35
Return of capital to parent company																			(38)		(38)			(505)	(505)			(505)
Ending balance (in shares) at Jun. 30, 2019			1,046	1						31					9					1
Ending balance at Jun. 30, 2019		31,131	$ 5,217	$ (41)	11,540	10,420	(238)	4,233	8,829	$ 1,222	4,767	2,866	(26)	14,316	$ 398	10,371	3,582	(35)	1,617	$ 38	4,480	(2,897)	(4)	6,818	1,102	1,479	4	2,585	4,233	8,759	8,908	(171)	22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		1,316				1,316			469			469		839			839		65			65		86		86		86		(29)		(29)
Other comprehensive income (loss)		(41)					(41)		1				1	(35)				(35)						(8)			(8)	(8)		(3)			(3)
Issuance of equity units	[1]	(198)			(198)
Stock issued (in shares)			4
Stock issued		171	$ 17		154
Stock-based compensation		12			12
Cash dividends on common stock		(649)				(649)			(211)			(211)		(394)			(394)							(51)		(51)		(51)		(118)		(118)
Contributions from noncontrolling interests		63						63																63
Distributions to noncontrolling interests		(43)						(43)																(43)					(43)
Net income (loss) attributable to noncontrolling interests		25						25																25					25
Other		4			4	0								0		(1)	1
Capital contributions from parent company														38		38								53	53			53	63	784	784
Return of capital to parent company									(2)		(2)								(43)		(43)			(250)	(250)			(250)
Ending balance (in shares) at Sep. 30, 2019			1,050	1						31					9					1
Ending balance at Sep. 30, 2019		$ 31,791	$ 5,234	$ (41)	$ 11,512	$ 11,087	$ (279)	$ 4,278	$ 9,086	$ 1,222	$ 4,765	$ 3,124	$ (25)	$ 14,764	$ 398	$ 10,408	$ 4,028	$ (70)	$ 1,639	$ 38	$ 4,437	$ (2,832)	$ (4)	$ 6,693	$ 905	$ 1,514	$ (4)	$ 2,415	$ 4,278	$ 9,393	$ 9,692	$ (318)	$ 19
[1]	See Note (F) under " Equity Units " for additional information.

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividends (in dollars per share)	$ 0.62	$ 0.62	$ 0.60	$ 0.60	$ 0.60	$ 0.58

Introduction

Introduction	9 Months Ended
	Sep. 30, 2019
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, 2018 have been derived from the audited financial statements of each registrant. In the opinion of each registrant's management, the information regarding such registrant furnished herein reflects all adjustments, which, except as otherwise disclosed, are of a normal recurring nature, necessary to present fairly the results of operations for the periods ended September 30, 2019 and 2018 . 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 results of operations, financial position, or cash flows of any registrant. Recently Adopted Accounting Standards In 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires lessees to recognize on the balance sheet a lease liability and a right-of-use asset for all leases. ASU 2016-02 also changes the recognition, measurement, and presentation of expense associated with leases and provides clarification regarding the identification of certain components of contracts that would represent a lease. The accounting required by lessors is relatively unchanged and there is no change to the accounting for existing leveraged leases. The registrants adopted the new standard effective January 1, 2019. See Note (L) for additional information and related disclosures. Goodwill and Other Intangible Assets Goodwill at September 30, 2019 and December 31, 2018 was as follows: At September 30, 2019 At December 31, 2018 (in millions) Southern Company $ 5,280 $ 5,315 Southern Company Gas: Gas distribution operations $ 4,034 $ 4,034 Gas marketing services 981 981 Southern Company Gas total $ 5,015 $ 5,015 Goodwill is not amortized but is subject to an annual impairment test during the fourth quarter of each year or more frequently if impairment indicators arise. A goodwill impairment charge of $32 million was recorded in the second quarter 2019 in contemplation of the July 22, 2019 sale of PowerSecure's utility infrastructure services business. In the third quarter 2019, impairment charges of $2 million and $3 million were recorded to goodwill and other intangible assets, net, respectively, in contemplation of the sale of PowerSecure's lighting business, which is expected to occur in the fourth quarter 2019. See Note (K) under " Southern Company " for additional information. Other intangible assets were as follows: At September 30, 2019 At December 31, 2018 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 (a) $ 211 $ (110 ) $ 101 $ 223 $ (94 ) $ 129 Trade names (a) 64 (23 ) 41 70 (21 ) 49 Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 PPA fair value adjustments (b) 389 (64 ) 325 405 (61 ) 344 Other 12 (8 ) 4 11 (5 ) 6 Total other intangible assets subject to amortization $ 740 $ (265 ) $ 475 $ 773 $ (235 ) $ 538 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (265 ) $ 550 $ 848 $ (235 ) $ 613 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments (b) $ 389 $ (64 ) $ 325 $ 405 $ (61 ) $ 344 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (99 ) $ 57 $ 156 $ (84 ) $ 72 Trade names 26 (9 ) 17 26 (7 ) 19 Wholesale gas services Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 Total other intangible assets subject to amortization $ 246 $ (168 ) $ 78 $ 246 $ (145 ) $ 101 (a) The decrease in the gross carrying amount during the nine months ended September 30, 2019 primarily reflects the reclassification to held for sale. See Note (K) for additional information. (b) The decrease in the gross carrying amount during the nine months ended September 30, 2019 reflects the sale of Plant Nacogdoches, partially offset by additional PPA fair value adjustments related to the acquisition of DSGP. See Note (K) under "Southern Power" for additional information. Amortization associated with other intangible assets was as follows: Three Months Ended Nine Months Ended September 30, 2019 (in millions) Southern Company (a) $ 14 $ 45 Southern Power (b) $ 4 $ 14 Southern Company Gas Gas marketing services $ 5 $ 17 Wholesale gas services (b) 2 6 Southern Company Gas total $ 7 $ 23 (a) Includes $6 million and $20 million for the three and nine months ended September 30, 2019 , respectively, recorded as a reduction to operating revenues. (b) Recorded as a reduction to operating revenues. Restricted Cash At December 31, 2018, Georgia Power had restricted cash related to the redemption of certain pollution control revenue bonds in January 2019. See Note (F) under " Financing Activities " for additional information. At both September 30, 2019 and December 31, 2018 , Southern Company Gas had restricted cash held as collateral for worker's compensation, life insurance, and long-term disability insurance. The following tables provide a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the registrants that had restricted cash at September 30, 2019 and/or December 31, 2018 : Southern Company Southern Company Gas (in millions) At September 30, 2019 Cash and cash equivalents $ 2,931 $ 59 Restricted cash: Other accounts and notes receivable 3 3 Total cash, cash equivalents, and restricted cash $ 2,935 (*) $ 62 (*) Total does not add due to rounding. Southern Company Georgia Power Southern Company Gas (in millions) At December 31, 2018 Cash and cash equivalents $ 1,396 $ 4 $ 64 Cash and cash equivalents held for sale 9 — — Restricted cash: Restricted cash — 108 — Other accounts and notes receivable 114 — 6 Total cash, cash equivalents, and restricted cash $ 1,519 $ 112 $ 70 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 recorded an adjustment of $10 million for the nine months ended September 30, 2019 and no material adjustments for the remaining periods reported. 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 had no inventory decrement at September 30, 2019 . Asset Retirement Obligations See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information regarding AROs. Details of the AROs included in the condensed balance sheets of Southern Company, Alabama Power, and Mississippi Power at September 30, 2019 are shown in the following table. There were no material changes in the AROs of Georgia Power or Southern Power during the first nine months of 2019. Southern Company Alabama Power Mississippi Power (in millions) Balance at December 31, 2018 $ 9,394 $ 3,210 $ 160 Liabilities incurred 35 — 1 Liabilities settled (223 ) (76 ) (28 ) Accretion 299 107 5 Cash flow revisions 455 312 57 Balance at September 30, 2019 $ 9,960 $ 3,553 $ 195 During 2019, Alabama Power recorded increases totaling approximately $312 million to its AROs primarily related to the CCR Rule and the related state rule based on management's completion of closure designs for all but one of its ash pond facilities. In the second quarter 2019, Mississippi Power recorded an increase of approximately $58 million to its AROs related to the CCR Rule, primarily associated with the ash pond facility at Plant Greene County, which is jointly owned with Alabama Power. The additional estimated costs to close these ash ponds under the planned closure-in-place methodology primarily relate to cost inputs from contractor bids, internal drainage and dewatering system designs, and increases in the estimated ash volumes. The cost estimate for the remaining Alabama Power ash pond facility will be updated within the next 12 months and the change could be material. As further analysis is performed and additional details are developed with respect to ash pond closures, the traditional electric operating companies expect to periodically update their ARO cost estimates. Additionally, the closure designs and plans in the States of Alabama and Georgia are subject to approval by environmental regulatory agencies. Absent continued recovery of ARO costs through regulated rates, Southern Company's and the traditional electric operating companies' results of operations, cash flows, and financial condition could be materially impacted. The ultimate outcome of these matters cannot be determined at this time.

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2019
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 of Alabama Power's, Georgia Power's, and Mississippi Power's regulatory clauses at September 30, 2019 and December 31, 2018 were as follows: Regulatory Clause Balance Sheet Line Item September 30, December 31, (in millions) Alabama Power Rate CNP Compliance Deferred under recovered regulatory clause revenues $ — $ 42 Other regulatory liabilities, deferred 55 — Rate CNP PPA Deferred under recovered regulatory clause revenues 45 25 Retail Energy Cost Recovery (*) Deferred under recovered regulatory clause revenues — 109 Other regulatory liabilities, deferred 21 — Natural Disaster Reserve Other regulatory liabilities, deferred 23 20 Georgia Power Fuel Cost Recovery Receivables – under recovered fuel clause revenues $ — $ 115 Other deferred credits and liabilities 1 — Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 18 $ 8 (*) In accordance with an accounting order issued on February 5, 2019 by the Alabama PSC, Alabama Power utilized $75 million of the 2018 Rate RSE refund liability to reduce the Rate ECR under recovered balance. See Note 2 to the financial statements under "Alabama Power – Rate ECR" in Item 8 of the Form 10-K for additional information. Alabama Power Petition for Certificate of Convenience and Necessity On September 6, 2019, Alabama Power filed a petition for a CCN with the Alabama PSC for authorization to procure additional generating capacity through the turnkey construction of a new combined cycle facility and long-term contracts for the purchase of power from others, both as more fully described below, as well as the acquisition of an existing combined cycle facility in Autauga County, AL (Autauga Combined Cycle Acquisition). In addition, Alabama Power will pursue approximately 200 MWs of certain demand side management and distributed energy resource programs. This filing was predicated on the results of Alabama Power's 2019 IRP provided to the Alabama PSC, which identified an approximately 2,400 -MW resource need for Alabama Power, driven by the need for additional winter reserve capacity. See Note (K) under " Alabama Power " for additional information regarding the Autauga Combined Cycle Acquisition. The procurement of these resources is subject to the satisfaction or waiver of certain conditions, including, among other customary conditions, approval by the Alabama PSC. The completion of the Autauga Combined Cycle Acquisition is also subject to (i) the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and (ii) approval by the FERC. All regulatory approvals are expected to be obtained by the end of the third quarter 2020. On May 8, 2019, Alabama Power entered into an Agreement for Engineering, Procurement, and Construction with Mitsubishi Hitachi Power Systems Americas, Inc. and Black & Veatch Construction, Inc. to construct an approximately 720 -MW combined cycle facility at Plant Barry (Plant Barry Unit 8), which is expected to be placed in service by the end of 2023. The capital investment associated with the construction of Plant Barry Unit 8 and the Autauga Combined Cycle Acquisition is currently estimated to total approximately $1.1 billion . Alabama Power also intends to procure through long-term PPAs approximately 640 MWs of additional generating capacity, which will consist of approximately 240 MWs of combined cycle generation expected to begin in 2020 and approximately 400 MWs of solar generation coupled with battery energy storage systems (solar/battery systems) expected to begin in 2022 through 2024. The terms of the agreements for the solar/battery systems permit Alabama Power to use the energy and retire the associated renewable energy credits (REC) in service of customers or to sell RECs, separately or bundled with energy. Upon certification, Alabama Power expects to recover costs associated with Plant Barry Unit 8 through its Rate CNP New Plant. Additionally, Alabama Power expects to recover costs associated with the Autauga Combined Cycle Acquisition through Rate RSE during the term of the existing power sales agreement and, on expiration of the agreement, through Rate CNP New Plant. The recovery of costs associated with laws, regulations, and other such mandates directed at the utility industry are expected to be recovered through Rate CNP Compliance. Alabama Power expects to recover the capacity-related costs associated with the PPAs through its Rate CNP PPA. In addition, fuel and energy-related costs are expected to be recovered through Rate ECR. Any remaining costs associated with the Autauga Combined Cycle Acquisition and Plant Barry Unit 8 will be incorporated through the annual filing of Rate RSE. See Note 2 to the financial statements under "Alabama Power" in Item 8 of the Form 10-K for additional information. The ultimate outcome of these matters cannot be determined at this time. Construction Work in Progress Accounting Order On October 1, 2019, the Alabama PSC acknowledged that Alabama Power would begin certain limited preparatory activities associated with Plant Barry Unit 8 construction to meet the target in-service date by authorizing Alabama Power to record the related costs as CWIP prior to the issuance of an order on the CCN petition. Should a CCN not be granted and Alabama Power does not proceed with the related construction of Plant Barry Unit 8, Alabama Power may transfer those costs and any costs that directly result from the non-issuance of the CCN to a regulatory asset which would be amortized over a five -year period. If the balance of incurred costs reaches 5% of the estimated in-service cost of the total project prior to issuance of an order on the CCN petition, Alabama Power will confer with the Alabama PSC regarding the appropriateness of additional authorization. Environmental Accounting Order On April 15, 2019, Alabama Power retired Plant Gorgas Units 8, 9, and 10 and reclassified approximately $654 million of the unrecovered asset balances to regulatory assets, which are being recovered over the units' remaining useful lives, the latest being through 2037, as established prior to the decision to retire. Additionally, approximately $700 million of net capitalized asset retirement costs were reclassified to a regulatory asset in accordance with accounting guidance provided by the Alabama PSC. The asset retirement costs are being recovered through 2055. See Note 2 to the financial statements under "Alabama Power – Environmental Accounting Order" and Note 6 in Item 8 of the Form 10-K for additional information. Georgia Power Rate Plans On June 28, 2019, Georgia Power filed a base rate case (Georgia Power 2019 Base Rate Case) with the Georgia PSC. The filing, as modified on September 24, 2019, includes a three -year Alternate Rate Plan with requested rate increases totaling $560 million , $144 million , and $233 million effective January 1, 2020, January 1, 2021, and January 1, 2022, respectively. These increases are based on a proposed retail ROE of 10.90% and a proposed equity ratio of 56% and reflect levelized revenue requirements during the three -year period, with the exception of incremental compliance costs related to CCR AROs, Demand-Side Management programs, and adjustments to the Municipal Franchise Fee tariff. Georgia Power has requested recovery of the proposed increases through its existing base rate tariffs as follows: Tariff 2020 2021 2022 (in millions) Traditional base: Levelized $ 210 $ — $ — CCR AROs 158 139 227 Environmental Compliance Cost Recovery 163 — — Demand-Side Management 12 1 1 Municipal Franchise Fee 17 3 5 Total (*) $ 560 $ 144 $ 233 (*) Totals may not add due to rounding. Georgia Power's filing primarily reflects requests to (i) address the impacts of the Tax Reform Legislation, (ii) recover the costs of recent and future capital investments in infrastructure designed to maintain high levels of reliability and superior customer service with updated depreciation rates, (iii) recover substantial storm damage expenses incurred and deferred since 2013 along with a reasonable level of storm damage expenses expected to be incurred during the three years ending December 31, 2022, and (iv) recover the costs necessary to comply with federal and state regulations for CCR AROs. In addition, the filing includes the following provisions: • Continuation of an allowed retail ROE range of 10.00% to 12.00% . • Continuation of the process whereby two-thirds of any earnings above the top of the allowed ROE range are shared with Georgia Power's customers and the remaining one-third are retained by Georgia Power. • Continuation of the option to file an Interim Cost Recovery tariff in the event earnings are projected to fall below the bottom of the ROE range during the three -year term of the plan. Georgia Power expects the Georgia PSC to issue a final order in this matter on December 17, 2019. The ultimate outcome of this matter cannot be determined at this time. Integrated Resource Plan In 2016, the Georgia PSC approved Georgia Power's triennial IRP, including recovery of costs up to $99 million through June 30, 2019 to preserve nuclear generation as an option at a future generation site in Stewart County, Georgia. In 2017, the Georgia PSC approved Georgia Power's decision to suspend work at the site due to changing economics, including lower load forecasts and fuel costs. In accordance with the Georgia PSC's order, costs incurred of approximately $50 million have been recorded as a regulatory asset. On July 16, 2019, the Georgia PSC voted to approve Georgia Power's triennial IRP (Georgia Power 2019 IRP) as modified by a stipulated agreement among Georgia Power, the staff of the Georgia PSC, and certain intervenors and further modified by the Georgia PSC. In the Georgia Power 2019 IRP, the Georgia PSC approved the decertification and retirement of Plant Hammond Units 1 through 4 ( 840 MWs) and Plant McIntosh Unit 1 ( 142.5 MWs) effective July 29, 2019. The Georgia PSC also approved the reclassification of the remaining net book values of the Plant Hammond and Plant McIntosh units (approximately $500 million and $40 million , respectively ), as well as any unusable materials and supplies inventory balances, upon retirement to a regulatory asset. Recovery of each unit's net book value will continue through December 31, 2019 as provided in the 2013 ARP. Additionally, approximately $295 million of net capitalized asset retirement costs were reclassified to a regulatory asset. For the regulatory asset balances remaining at December 31, 2019, Georgia Power requested recovery in the Georgia Power 2019 Base Rate Case as follows: (i) the net book values of Plant Mitchell Unit 3 (approximately $8 million at September 30, 2019 ) and Plant McIntosh Unit 1 , any unusable materials and supplies inventory, and the future generation site in Stewart County, Georgia over a three -year period ending December 31, 2022 and (ii) the net book values of Plant Hammond Units 1 through 4 over a period equal to the applicable unit's remaining useful life through 2035. The timing of recovery of the related ARO costs will be determined in the Georgia Power 2019 Base Rate Case. The ultimate outcome of these matters cannot be determined at this time. Also in the Georgia Power 2019 IRP, the Georgia PSC approved Georgia Power's proposed environmental compliance strategy associated with ash pond and certain landfill closures and post-closure care in compliance with the CCR Rule and the related state rule. In the Georgia Power 2019 Base Rate Case, Georgia Power requested recovery of the under recovered balance of these compliance costs at December 31, 2019 (approximately $157 million at September 30, 2019 ) over a three -year period ending December 31, 2022 and recovery of estimated compliance costs of $277 million for 2020, $395 million for 2021, and $655 million for 2022 over three -year periods ending December 31, 2022, 2023, and 2024, respectively. The ultimate outcome of this matter cannot be determined at this time. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information regarding Georgia Power's AROs. Additionally, the Georgia PSC rejected a request to certify approximately 25 MWs of capacity at Plant Scherer Unit 3 for the retail jurisdiction beginning January 1, 2020 following the expiration of a wholesale PPA. Georgia Power may offer such capacity in the wholesale market or to the retail jurisdiction in a future IRP. The ultimate outcome of this matter cannot be determined at this time but is not expected to have a material impact on Georgia Power's or Southern Company's financial statements. The Georgia PSC also approved Georgia Power to (i) issue requests for proposals (RFP) for capacity beginning in 2022 or 2023 and in 2026, 2027, or 2028; (ii) procure up to an additional 2,210 MWs of renewable resources through competitive RFPs; and (iii) invest in a portfolio of up to 80 MWs of battery energy storage technologies. See "Rate Plans" herein for additional information regarding the Georgia Power 2019 Base Rate Case. Nuclear Construction See Note 2 to the financial statements under "Georgia Power – Nuclear Construction" in Item 8 of the Form 10-K for additional information regarding Georgia Power's construction of Plant Vogtle Units 3 and 4, the joint ownership agreements and related funding agreement, VCM reports, and the NCCR tariff. 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. 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) $ 8.0 Construction contingency estimate 0.4 Total project capital cost forecast (a)(b) 8.4 Net investment as of September 30, 2019 (b) (5.5 ) Remaining estimate to complete (a) $ 2.9 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $300 million . (b) Net of $1.7 billion received from Toshiba under the Guarantee Settlement Agreement and approximately $188 million in related Customer Refunds. As of September 30, 2019 , approximately $30 million of the construction contingency estimate was allocated to the base capital cost forecast for cost risks including, among other factors, attracting and retaining craft labor; adding resources for supervision, field support, project management, initial test program, and start-up; and procurement. As and when construction contingency is spent, Georgia Power may request the Georgia PSC to evaluate those expenditures for rate recovery. Georgia Power estimates that its financing costs for construction of Plant Vogtle Units 3 and 4 will total approximately $3.1 billion , of which $2.1 billion had been incurred through September 30, 2019 . In April 2019, Southern Nuclear completed a cost and schedule validation process to verify and update quantities of commodities remaining to install, labor hours to install remaining quantities and related productivity, testing and system turnover requirements, and forecasted staffing needs and related costs. This process confirmed the estimated total project capital cost forecast for Plant Vogtle Units 3 and 4. The expected in-service dates of November 2021 for Unit 3 and November 2022 for Unit 4, as previously approved by the Georgia PSC, remain unchanged. On April 30, 2019, as requested by the staff of the Georgia PSC, Georgia Power reported the results of the cost and schedule validation process to the Georgia PSC. As construction continues and testing and system turnover activities increase, challenges with management of contractors, subcontractors, and vendors; supervision of craft labor and related craft labor 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, and/or installation and the initial testing and start-up, including any required engineering changes, of plant systems, structures, or components (some of which are based on new technology that only recently began initial operation in the global nuclear industry at this scale), or regional transmission upgrades, any of which may require additional labor and/or materials; or other issues could arise and change the projected schedule and estimated cost. The April 2019 cost and schedule validation process established target values for monthly construction production and system turnover activities as part of a strategy to maintain and, where possible, build margin to the approved in-service dates. To support that strategy, monthly production and activity target values will continue to increase significantly throughout the remainder of 2019 and into 2020. To meet these increasing monthly targets, existing craft construction productivity must improve and additional craft laborers (particularly electrical and pipefitter craft labor), as well as additional supervision and other field support resources, must be retained and deployed. 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. 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 $11 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 the 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, 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'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 and MEAG SPVJ to provide funding with respect to MEAG SPVJ's ownership interest in Plant Vogtle Units 3 and 4 under certain circumstances. On January 14, 2019, Georgia Power, MEAG, and MEAG SPVJ entered into an agreement to implement the provisions of the MEAG Term Sheet. On February 18, 2019, Georgia Power, the other Vogtle Owners, and MEAG'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. The ultimate outcome of these matters cannot be determined at this time. Regulatory Matters In 2009, the Georgia PSC voted to certify construction of Plant Vogtle Units 3 and 4 with a certified capital cost of $4.418 billion . In addition, in 2009 the Georgia PSC approved inclusion of the Plant Vogtle Units 3 and 4 related CWIP accounts in rate base, and the State of Georgia enacted the Georgia Nuclear Energy Financing Act, which allows Georgia Power to recover financing costs for Plant Vogtle Units 3 and 4. Financing costs are recovered on all applicable certified costs through annual adjustments to the NCCR tariff up to the certified capital cost of $4.418 billion . At September 30, 2019 , Georgia Power had recovered approximately $2.1 billion of financing costs. Financing costs related to capital costs above $4.418 billion will be recovered through AFUDC; 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 2018, the Georgia PSC approved Georgia Power's request to increase the NCCR tariff by $88 million annually, effective January 1, 2019. Georgia Power expects to file on November 1, 2019 to decrease the NCCR tariff by approximately $65 million annually, effective January 1, 2020, pending Georgia PSC approval. Georgia Power is required to file semi-annual VCM reports with the Georgia PSC by February 28 and August 31 of each year. In 2013, in connection with the eighth VCM report, the Georgia PSC approved a stipulation between Georgia Power and the staff of the Georgia PSC to waive the requirement to amend the Plant Vogtle Units 3 and 4 certificate in accordance with the 2009 certification order until the completion of Plant Vogtle Unit 3, or earlier if deemed appropriate by the Georgia PSC and Georgia Power. In 2016, the Georgia PSC voted to approve a settlement agreement (Vogtle Cost Settlement Agreement) resolving certain prudency matters in connection with the fifteenth VCM report. In December 2017, the Georgia PSC voted to approve (and issued its related order on January 11, 2018) Georgia Power's seventeenth VCM report and modified the Vogtle Cost Settlement Agreement. The Vogtle Cost Settlement Agreement, as modified by the January 11, 2018 order, resolved the following regulatory matters related to Plant Vogtle Units 3 and 4: (i) none of the $3.3 billion of costs incurred through December 31, 2015 and reflected in the fourteenth VCM report should be disallowed from rate base on the basis of imprudence; (ii) the Contractor Settlement Agreement was reasonable and prudent and none of the amounts paid pursuant to the Contractor Settlement Agreement should be disallowed from rate base on the basis of imprudence; (iii) (a) capital costs incurred up to $5.68 billion would be presumed to be reasonable and prudent with the burden of proof on any party challenging such costs, (b) Georgia Power would have the burden to show that any capital costs above $5.68 billion were prudent, and (c) a revised capital cost forecast of $7.3 billion (after reflecting the impact of payments received under the Guarantee Settlement Agreement and related Customer Refunds) was found reasonable; (iv) construction of Plant Vogtle Units 3 and 4 should be completed, with Southern Nuclear serving as project manager and Bechtel as primary contractor; (v) approved and deemed reasonable Georgia Power's revised schedule placing Plant Vogtle Units 3 and 4 in service in November 2021 and November 2022, respectively; (vi) confirmed that the revised cost forecast does not represent a cost cap and that prudence decisions on cost recovery will be made at a later date, consistent with applicable Georgia law; (vii) reduced the ROE used to calculate the NCCR tariff (a) from 10.95% (the ROE rate setting point authorized by the Georgia PSC in the 2013 ARP) to 10.00% effective January 1, 2016, (b) from 10.00% to 8.30% , effective January 1, 2020, and (c) from 8.30% to 5.30% , effective January 1, 2021 (provided that the ROE in no case will be less than Georgia Power's average cost of long-term debt); (viii) reduced the ROE used for AFUDC equity for Plant Vogtle Units 3 and 4 from 10.00% to Georgia Power's average cost of long-term debt, effective January 1, 2018; and (ix) agreed that upon Unit 3 reaching commercial operation, retail base rates would be adjusted to 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 $100 million in 2018 and are estimated to have negative earnings impacts of approximately $70 million in 2019 and an aggregate of approximately $650 million from 2020 to 2022. 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. On January 9, 2019, GIPL, PSE, and Georgia Watch filed an appeal of this decision with the Georgia Court of Appeals. On October 29, 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. 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 nineteen VCM reports covering the period through June 30, 2018, including total construction capital costs incurred through that date of $5.4 billion (before $1.7 billion of payments received under the Guarantee Settlement Agreement and approximately $188 million in related Customer Refunds). On August 30, 2019, Georgia Power filed its twentieth VCM report concurrently with its twenty-first VCM report with the Georgia PSC, which requested approval of $1.2 billion of construction capital costs incurred from July 1, 2018 through June 30, 2019. In the nineteenth VCM, the Georgia PSC deferred approval of $51.6 million of expenditures related to Georgia Power's portion of an administrative claim filed in the Westinghouse bankruptcy proceedings. On June 20, 2019, Georgia Power, acting for itself and as agent for the other Vogtle Owners, entered into a settlement agreement related to the administrative claim filed in the Westinghouse bankruptcy proceedings. Accordingly, in the twentieth/twenty-first VCM report, Georgia Power also requested approval of $21.5 million of associated expenditures previously deferred for approval by the Georgia PSC. The remaining $30.1 million deferred for approval was refunded to Georgia Power and credited to the total construction capital costs. The ultimate outcome of these matters cannot be determined at this time. DOE Financing At September 30, 2019 , Georgia Power had borrowed $3

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2019
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 Each registrant is subject to certain claims and legal actions arising in the ordinary course of business. In addition, the business activities of Southern Company's subsidiaries are subject to extensive governmental regulation related to public health and the environment, such as laws and regulations governing air, water, land, and protection of natural resources. Litigation over environmental issues and claims of various types, including property damage, personal injury, common law nuisance, and citizen enforcement of environmental laws and regulations, has occurred throughout the U.S. This litigation has included claims for damages alleged to have been caused by CO 2 and other emissions, CCR, and alleged exposure to hazardous materials, and/or requests for injunctive relief in connection with such matters. The ultimate outcome of such pending or potential litigation 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. 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 March 2018, the court issued an order granting, in part, the defendants' motion to dismiss. The court dismissed certain claims against certain officers of Southern Company and Mississippi Power and dismissed the allegations related to a number of the statements that plaintiffs challenged as being false or misleading. In April 2018, the defendants filed a motion for reconsideration of the court's order, seeking dismissal of the remaining claims in the lawsuit. In August 2018, the court denied the motion for reconsideration and denied a motion to certify the issue for interlocutory appeal. On August 22, 2019, the court certified the plaintiffs' proposed class. On September 5, 2019, 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 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 April 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 May 2018, the court entered an order staying this lawsuit until 30 days after the resolution of any dispositive motions or any settlement, whichever is earlier, in the securities class action. On August 5, 2019, the court granted a motion filed by the plaintiff on July 17, 2019 to substitute a new named plaintiff, Martin J. Kobuck, in place of Helen E. Piper Survivor's Trust. Southern Company believes these legal challenges have no merit; however, the ultimate outcome of these matters cannot be determined at this time. 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 June 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, on February 13, 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. On October 23, 2019, the Georgia PSC issued an order that found and concluded that Georgia Power has appropriately implemented the municipal franchise fee schedule. On March 6, 2019, Georgia Power filed a notice of appeal with the Georgia Court of Appeals regarding the Superior Court of Fulton County's February 2019 order. Georgia Power believes the plaintiffs' claims have no merit. The amount of any possible losses cannot be calculated at this time because, among other factors, it is unknown whether conditional class certification will be upheld and the ultimate composition of any class and whether any losses would be subject to recovery from any municipalities. The ultimate outcome of this matter cannot be determined at this time. 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 the first quarter 2019, Mississippi Power and Southern Company filed motions to dismiss, which were denied by the arbitration panel on May 10, 2019. On September 27, 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 . Southern Company and Mississippi Power believe these legal challenges have no merit; however, an adverse outcome in either of these proceedings could have a material impact on Mississippi Power's financial statements and an adverse outcome in the arbitration case could have a material impact on Southern Company's financial statements. The ultimate outcome of these matters cannot be determined at this time. In November 2018, Ray C. Turnage and 10 other individual plaintiffs filed a putative class action complaint against Mississippi Power and the three current 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 on March 14, 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. Mississippi Power believes this legal challenge has no merit; however, an adverse outcome in this proceeding could have a material impact on Mississippi Power's financial statements. The ultimate outcome of this matter cannot be determined at this time. Southern Power Southern Power indirectly owns a 51% membership interest in RE Roserock LLC (Roserock), the owner of the Roserock facility in Pecos County, Texas. Prior to the facility being placed in service in 2016, certain solar panels were damaged during installation by the construction contractor, McCarthy Building Companies, Inc. (McCarthy), and certain solar panels were damaged by a hail event that also occurred during construction. In connection therewith, Southern Power withheld payment of approximately $26 million to the construction contractor, which placed a lien on the Roserock facility for the same amount. In 2017, Roserock filed a lawsuit in the state district court in Pecos County, Texas against XL Insurance America, Inc. and North American Elite Insurance Company seeking recovery from an insurance policy for damages resulting from the hail event and McCarthy's installation practices. In June 2018, the court granted Roserock's motion for partial summary judgment, finding that the insurers were in breach of contract and in violation of the Texas Insurance Code for failing to pay any monies owed for the hail claim. Separate lawsuits were filed between Roserock and McCarthy, as well as other parties, and that litigation was consolidated in the U.S. District Court for the Western District of Texas. On April 18, 2019, Roserock and the parties to the state and federal lawsuits executed a settlement agreement and mutual release that resolved both lawsuits. Following execution of the agreement, the lawsuits were dismissed, Southern Power paid McCarthy the amounts previously withheld, and McCarthy released its lien. As part of the settlement, Roserock received funds that covered all related legal costs, damages, and the replacement costs of certain solar panels. Funds received by Southern Power in excess of the initial replacement costs were recognized as a gain and included in other income (expense), net, with a portion allocated to noncontrolling interests. As a result, Southern Power recognized a $12 million after-tax gain in the second quarter 2019. 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 $16 million and $23 million as of September 30, 2019 and December 31, 2018 , respectively. 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. Southern Company Gas' environmental remediation liability was $278 million and $294 million as of September 30, 2019 and December 31, 2018 , 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 recoverable from customers through rate mechanisms approved by the applicable state regulatory agencies of the natural gas distribution utilities, with the exception of one site representing $2 million of the total accrued remediation costs. 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 Southern Company, Georgia Power, or Southern Company Gas. Nuclear Fuel Disposal Costs In 2014, Alabama Power and Georgia Power filed lawsuits against the U.S. government for the costs of continuing to store spent nuclear fuel at Plants Farley, Hatch, and Vogtle Units 1 and 2 for the period from January 1, 2011 through December 31, 2013. The damage period was subsequently extended to December 31, 2014. On June 12, 2019, the Court of Federal Claims granted Alabama Power's and Georgia Power's motion for summary judgment on damages not disputed by the U.S. government, awarding those undisputed damages to Alabama Power and Georgia Power. However, those undisputed damages are not collectible and no amounts will be recognized in the financial statements until the court enters final judgment on the remaining damages. The final outcome of these matters cannot be determined at this time. However, Alabama Power and Georgia Power expect to credit any recoveries for the benefit of customers in accordance with direction from their respective PSC; therefore, no material impact on Southern Company's, Alabama Power's, or Georgia Power's net income is expected. Other Matters Alabama Power On May 17, 2019, the Alabama Department of Environmental Management (ADEM) issued a proposed administrative order assessing a penalty of $250,000 to Alabama Power for unpermitted discharge of fluids and/or pollutants to groundwater and/or soils at Plant Gadsden. The order was finalized and Alabama Power paid the penalty on September 16, 2019. On October 16, 2019, Alabama Power agreed to a consent order regarding a fish kill investigation. The consent order requires Alabama Power to pay approximately $50,000 to ADEM in civil penalties and approximately $172,000 to the Alabama Department of Conservation and Natural Resources in fish restocking costs. The ultimate outcome of this matter cannot be determined at this time. Mississippi Power In conjunction with Southern Company's sale of Gulf Power, Mississippi Power and Gulf Power have committed 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 January 15, 2019, Gulf Power provided notice to Mississippi Power that Gulf Power will retire its share of the generating capacity of Plant Daniel on January 15, 2024. Mississippi Power has the option to purchase Gulf Power's ownership interest for $1 on January 15, 2024, provided that Mississippi Power exercises the option no later than 120 days prior to that date. Mississippi Power is assessing the potential operational and economic effects of Gulf Power's notice. The ultimate outcome of these matters remains subject to completion of Mississippi Power's evaluations and applicable regulatory approvals, including by the FERC and the Mississippi PSC, and cannot be determined at this time. See Note (K) under " Southern Company " for information regarding the sale of Gulf Power. Southern Company Gas See Note 3 to the financial statements in Item 8 of the Form 10-K under "Other Matters – Southern Company Gas" for information on a natural gas storage facility consisting of two salt dome caverns in Louisiana. As of September 30, 2019, management no longer plans to obtain the core samples during 2020 that are necessary to determine the composition of the sheath surrounding the edge of the salt dome. Core sampling is a requirement of the Louisiana Department of Natural Resources to put the cavern back in service; as a result, the cavern will not return to service by 2021. This change in plan, which affects the future operation of the entire storage facility, resulted in a pre-tax impairment charge of $92 million ( $65 million after-tax). Southern Company Gas will continue to monitor the pressure and overall structural integrity of the entire facility pending any future decisions regarding decommissioning. Southern Company Gas has two other natural gas storage facilities located in California and Texas, which could be impacted by ongoing changes in the U.S. natural gas storage market. Recent sales of natural gas storage facilities have resulted in losses for the sellers and may imply an impact on future rates and/or asset values. Sustained diminished natural gas storage values could trigger impairment of either of these natural gas storage facilities, which have a combined net book value of $328 million at September 30, 2019 . The ultimate outcome of these matters cannot be determined at this time, but could have a material impact on Southern Company's and Southern Company Gas' financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS	REVENUE FROM CONTRACTS WITH CUSTOMERS The registrants generate revenues from a variety of sources, some of which are excluded from the scope of ASC 606, Revenue from Contracts with Customers (ASC 606), such as leases, derivatives, and certain cost recovery mechanisms. See Note 1 to the financial statements under "Recently Adopted Accounting Standards – Revenue" in Item 8 of the Form 10-K for additional information on the adoption of ASC 606 for revenue from contracts with customers and Note 1 to the financial statements under "Revenues" and "Other Taxes" in Item 8 of the Form 10-K for additional information on the revenue policies of the registrants. For additional information on revenues accounted for under other accounting guidance, see Notes (J) and (L) for energy-related derivative contracts and lessor revenues, respectively, Note 1 to the financial statements under "Revenues – Southern Company Gas" in Item 8 of the Form 10-K for alternative revenue programs at the natural gas distribution utilities, and Note 2 to the financial statements in Item 8 of the Form 10-K for cost recovery mechanisms. The following tables disaggregate revenue sources for the three and nine months ended September 30, 2019 and 2018 : For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Company Operating revenues Retail electric revenues (a) Residential $ 2,056 $ 2,148 $ 4,832 $ 5,266 Commercial 1,508 1,527 3,859 4,084 Industrial 916 901 2,356 2,471 Other 32 29 89 92 Natural gas distribution revenues (b) 445 433 2,169 2,299 Alternative revenue programs (c) — 5 — (23 ) Total retail electric and gas distribution revenues $ 4,957 $ 5,043 $ 13,305 $ 14,189 Wholesale energy revenues (d)(e) 477 521 1,254 1,458 Wholesale capacity revenues (e) 148 177 413 479 Other natural gas revenues (f)(g) 53 54 492 530 Other revenues (h) 360 364 1,041 1,502 Total operating revenues $ 5,995 $ 6,159 $ 16,505 $ 18,158 (a) Retail electric revenues include $8 million , $17 million , $24 million , and $54 million of revenues accounted for as leases for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and a net increase/(reduction) of $(155) million , $(98) million , $(272) million , and $4 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, from certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Natural gas distribution revenues include $3 million for each of the three months ended September 30, 2019 and 2018 and $11 million for each of the nine months ended September 30, 2019 and 2018 of revenues not accounted for under ASC 606. (c) Alternative revenue program revenues are presented net of any previously recognized program amounts billed to customers during the same accounting period. (d) Wholesale energy revenues include $28 million , $63 million , $109 million , and $217 million of revenues accounted for as derivatives for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, primarily related to physical energy sales in the wholesale electricity market. (e) Wholesale energy revenues include $141 million , $130 million , $324 million , and $318 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and wholesale capacity revenues include $15 million , $31 million , $62 million , and $92 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, related to PPAs accounted for as leases. (f) Other natural gas revenues related to Southern Company Gas' energy and risk management activities are presented net of the related costs of those activities and include gross third-party revenues of $1.1 billion , $1.6 billion , $4.3 billion , and $4.8 billion for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of which $0.7 billion , $0.9 billion , $2.7 billion , and $2.7 billion , respectively, relates to contracts that are accounted for as derivatives. See Note (M) under " Southern Company Gas " for additional information on the components of wholesale gas services operating revenues. (g) Other natural gas revenues include $10 million and $37 million for the three and nine months ended September 30, 2019 , respectively, of revenues not accounted for under ASC 606, including $8 million and $24 million , respectively, of revenues accounted for as leases. (h) Other revenues include $93 million , $92 million , $278 million , and $274 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of revenues not accounted for under ASC 606, including $33 million , $35 million , $104 million , and $106 million , respectively, accounted for as leases. Alabama Power Georgia Power Mississippi Power (in millions) For the Three Months Ended September 30, 2019 Operating revenues Retail revenues (a)(b) Residential $ 796 $ 1,174 $ 86 Commercial 493 932 83 Industrial 398 439 79 Other 7 22 3 Total retail electric revenues $ 1,694 $ 2,567 $ 251 Wholesale energy revenues (c) 48 25 114 Wholesale capacity revenues 25 14 1 Other revenues (b)(d) 74 149 4 Total operating revenues $ 1,841 $ 2,755 $ 370 For the Three Months Ended September 30, 2018 Operating revenues Retail revenues (a)(b) Residential $ 721 $ 1,142 $ 85 Commercial 464 877 82 Industrial 392 385 86 Other 7 21 1 Total retail electric revenues $ 1,584 $ 2,425 $ 254 Wholesale energy revenues (c) 62 33 97 Wholesale capacity revenues 26 14 1 Other revenues (b)(d) 68 121 6 Total operating revenues $ 1,740 $ 2,593 $ 358 (a) Retail revenues at Alabama Power, Georgia Power, and Mississippi Power include a net reduction of $(64) million , $(83) million , and $(8) million , respectively, for the three months ended September 30, 2019 and $(12) million , $(47) million , and $(3) million , respectively, for the three months ended September 30, 2018 related to certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Retail revenues and other revenues at Georgia Power include $8 million and $10 million , respectively, for the three months ended September 30, 2019 and $17 million and $34 million , respectively, for the three months ended September 30, 2018 of revenues accounted for as leases. (c) Wholesale energy revenues at Alabama Power, Georgia Power, and Mississippi Power include $3 million , $4 million , and $1 million , respectively, for the three months ended September 30, 2019 and $6 million , $8 million , and $1 million , respectively, for the three months ended September 30, 2018 accounted for as derivatives primarily related to physical energy sales in the wholesale electricity market. (d) Other revenues at Alabama Power and Georgia Power include $36 million and $26 million , respectively, for the three months ended September 30, 2019 and $27 million and $28 million , respectively, for the three months ended September 30, 2018 of revenues not accounted for under ASC 606. Alabama Power Georgia Power Mississippi Power (in millions) For the Nine Months Ended September 30, 2019 Operating revenues Retail revenues (a)(b) Residential $ 1,923 $ 2,693 $ 216 Commercial 1,266 2,372 221 Industrial 1,077 1,055 224 Other 20 61 8 Total retail electric revenues $ 4,286 $ 6,181 $ 669 Wholesale energy revenues (c) 183 66 285 Wholesale capacity revenues 77 41 2 Other revenues (b)(d) 216 418 14 Total operating revenues $ 4,762 $ 6,706 $ 970 For the Nine Months Ended September 30, 2018 Operating revenues Retail revenues (a)(b) Residential $ 1,848 $ 2,671 $ 209 Commercial 1,238 2,343 212 Industrial 1,103 1,036 233 Other 19 62 6 Total retail electric revenues $ 4,208 $ 6,112 $ 660 Wholesale energy revenues (c) 234 99 272 Wholesale capacity revenues 75 41 6 Other revenues (b)(d) 199 349 18 Total operating revenues $ 4,716 $ 6,601 $ 956 (a) Retail revenues at Alabama Power, Georgia Power, and Mississippi Power include a net increase/(reduction) of $(132) million , $(135) million , and $(5) million , respectively, for the nine months ended September 30, 2019 and $113 million , $(35) million , and $(11) million , respectively, for the nine months ended September 30, 2018 related to certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Retail revenues and other revenues at Georgia Power include $24 million and $33 million , respectively, for the nine months ended September 30, 2019 and $54 million and $100 million , respectively, for the nine months ended September 30, 2018 of revenues accounted for as leases. (c) Wholesale energy revenues at Alabama Power, Georgia Power, and Mississippi Power include $8 million , $12 million , and $2 million , respectively, for the nine months ended September 30, 2019 and $14 million , $21 million , and $3 million , respectively, for the nine months ended September 30, 2018 accounted for as derivatives primarily related to physical energy sales in the wholesale electricity market. (d) Other revenues at Alabama Power and Georgia Power include $95 million and $88 million , respectively, for the nine months ended September 30, 2019 and $79 million and $80 million , respectively, for the nine months ended September 30, 2018 of revenues not accounted for under ASC 606. For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Power PPA capacity revenues (a) $ 131 $ 168 $ 384 $ 450 PPA energy revenues (a) 339 336 857 892 Non-PPA revenues (b) 101 126 276 347 Other revenues 3 5 10 10 Total operating revenues $ 574 $ 635 $ 1,527 $ 1,699 (a) PPA capacity revenues include $31 million , $47 million , $111 million , and $141 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and PPA energy revenues include $151 million , $139 million , $349 million , and $342 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, related to PPAs accounted for as leases. (b) Non-PPA revenues include $20 million , $47 million , $87 million , and $176 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of revenues from short-term sales related to physical energy sales from uncovered capacity in the wholesale electricity market. For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Company Gas Operating revenues Natural gas distribution revenues (a) Residential $ 162 $ 149 $ 992 $ 1,082 Commercial 42 45 277 313 Transportation 204 203 673 708 Industrial 3 4 25 28 Other 34 32 202 168 Alternative revenue programs (b) — 5 — (23 ) Total natural gas distribution revenues $ 445 $ 438 $ 2,169 $ 2,276 Gas pipeline investments (c) 8 8 24 24 Wholesale gas services (d) (4 ) (10 ) 110 121 Gas marketing services (e) 39 44 326 403 Other revenues 10 12 32 37 Total operating revenues $ 498 $ 492 $ 2,661 $ 2,861 (a) Natural gas distribution revenues include $3 million for each of the three months ended September 30, 2019 and 2018 and $11 million for each of the nine months ended September 30, 2019 and 2018 of revenues not accounted for under ASC 606. (b) Alternative revenue program revenues are presented net of any previously recognized program amounts billed to customers during the same accounting period. (c) Revenues from gas pipeline investments include $8 million and $24 million for the three and nine months ended September 30, 2019 , respectively, accounted for as leases. (d) Wholesale gas services revenues are presented net of the related costs associated with its energy trading and risk management activities. Operating revenues, as presented, include gross third-party revenues of $1.1 billion , $1.6 billion , $4.3 billion , and $4.8 billion for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of which $0.7 billion , $0.9 billion , $2.7 billion , and $2.7 billion , respectively, relates to contracts accounted for as derivatives. See Note (M) under " Southern Company Gas " for additional information on the components of wholesale gas services operating revenues. (e) Gas marketing services include $2 million for the three months ended September 30, 2019 and $13 million and $4 million for the nine months ended September 30, 2019 and 2018 , respectively, of revenues not accounted for under ASC 606. Contract Balances The following table reflects the closing balances of receivables, contract assets, and contract liabilities related to revenues from contracts with customers as of September 30, 2019 and December 31, 2018 : Receivables Contract Assets Contract Liabilities September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 (in millions) Southern Company $ 2,523 $ 2,630 $ 132 $ 102 $ 58 $ 32 Alabama Power 713 520 2 — 12 12 Georgia Power 993 721 91 58 15 7 Mississippi Power 94 100 — — 6 — Southern Power 132 118 — — 3 11 Southern Company Gas 441 952 — — 1 2 As of September 30, 2019 and December 31, 2018 , 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. Mississippi Power had contract liabilities for cash collections recognized in advance of revenue for operating agreements associated with a tolling arrangement accounted for as a sales-type lease. Southern Company's unregulated distributed generation business had $31 million and $39 million of contract assets and $23 million and $11 million of contract liabilities at September 30, 2019 and December 31, 2018 , respectively, remaining for outstanding performance obligations. The following table reflects revenue from contracts with customers recognized in the three and nine months ended September 30, 2019 included in the contract liability at December 31, 2018 : Three Months Ended Nine Months Ended (in millions) Southern Company $ 4 $ 29 Southern Power — 11 Revenues recognized in the three and nine months ended September 30, 2019 , which were included in contract liabilities at December 31, 2018 , were immaterial for Alabama Power, Georgia Power, and Southern Company Gas. Remaining Performance Obligations The traditional electric operating companies and Southern Power have long-term contracts with customers in which revenues are recognized when the performance obligations are satisfied during 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. Registrants with revenues from contracts with customers related to these performance obligations remaining at September 30, 2019 expect the revenues to be recognized as follows: 2019 (remaining) 2020 2021 2022 2023 Thereafter (in millions) Southern Company $ 138 $ 419 $ 345 $ 326 $ 317 $ 2,256 Alabama Power 6 23 27 23 22 140 Georgia Power 15 56 47 31 32 83 Southern Power 61 309 291 290 283 2,180 Revenues expected to be recognized for performance obligations remaining at September 30, 2019 were immaterial for Mississippi Power.

Consolidated Entities and Equit

Consolidated Entities and Equity Method Investments	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS	CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS Southern Power Consolidated Variable Interest Entities See Note 7 to the financial statements in Item 8 of the Form 10-K for additional information on Southern Power's consolidated VIEs. 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. In 2018, Southern Power sold noncontrolling interests in SP Solar and SP Wind. Southern Power continues to consolidate each entity, as the primary beneficiary of each VIE, since it controls the most significant activities of each entity, including operating and maintaining their assets. Transfers and sales of the assets in the VIEs are subject to limited 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. In August 2019, Southern Power completed the acquisition of a majority interest in DSGP and gained control of its most significant activities. As a result, Southern Power became the primary beneficiary of this VIE and began accounting for it as a consolidated entity. See Note (K) under "Southern Power" for additional information. SP Solar At September 30, 2019 , SP Solar had total assets of $6.5 billion , total liabilities of $383 million , and noncontrolling interests of $1.2 billion . 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. SP Wind At September 30, 2019 , SP Wind had total assets of $2.5 billion , total liabilities of $132 million , and noncontrolling interests of $46 million . 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 Company Gas See Note 7 to the financial statements in Item 8 of the Form 10-K for additional information on Southern Company Gas' equity method investments. Equity Method Investments The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2019 and December 31, 2018 and related income from those investments for the three - and nine -month periods ended September 30, 2019 and 2018 were as follows: Investment Balance September 30, 2019 December 31, 2018 (in millions) SNG (a) $ 1,210 $ 1,261 Atlantic Coast Pipeline (b) 109 83 PennEast Pipeline 80 71 Other (c) 88 123 Total $ 1,487 $ 1,538 (a) Decrease primarily relates to the continued amortization of deferred tax assets established upon acquisition. (b) The Atlantic Coast Pipeline has a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Southern Company Gas guarantees 5% of the outstanding borrowings under this facility; this guarantee totaled $85 million as of September 30, 2019. (c) Decrease primarily relates to the sale of Triton. Earnings from Equity Method Investments Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) SNG $ 30 $ 29 $ 104 $ 95 Atlantic Coast Pipeline 3 1 9 4 PennEast Pipeline 2 2 5 4 Other (*) — 2 (3 ) 5 Total $ 35 $ 34 $ 115 $ 108 (*) Decrease primarily relates to the sale of Triton. SNG Selected financial information of SNG for the three and nine months ended September 30, 2019 and 2018 is as follows: Income Statement Information Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) Revenues $ 152 $ 145 $ 473 $ 451 Operating income 82 71 274 230 Net income 60 58 208 190 Atlantic Coast and PennEast Pipelines In 2014, Southern Company Gas entered into a joint venture, whereby it holds a 5% ownership interest in the Atlantic Coast Pipeline, an interstate pipeline company which will develop and operate a 605 -mile natural gas pipeline in North Carolina, Virginia, and West Virginia with expected initial transportation capacity of 1.5 Bcf per day. The Atlantic Coast Pipeline has experienced challenges to its permits since construction began in 2018. On October 4, 2019, the U.S. Supreme Court agreed to hear Atlantic Coast Pipeline's appeal of a lower court ruling that overturned a key permit for the project. The delays resulting from the permitting issues have impacted the cost and schedule for the project. As a result, total current project cost estimates have increased from between $7.0 billion and $7.8 billion ( $350 million and $390 million for Southern Company Gas) to between $7.3 billion and $7.8 billion ( $365 million and $390 million for Southern Company Gas), excluding financing costs. The operator of the joint venture has indicated that it currently expects to complete construction by the end of 2021 and place the project in service shortly thereafter. Also in 2014, Southern Company Gas entered into a partnership in which it holds a 20% ownership interest in the PennEast Pipeline, an interstate pipeline company formed to develop and operate a 118 -mile natural gas pipeline between New Jersey and Pennsylvania. The expected initial transportation capacity of 1.0 Bcf per day is under long-term contracts, mainly with public utilities and other market-serving entities, such as electric generation companies, in New Jersey, Pennsylvania, and New York. On September 10, 2019, an appellate court ruled that the PennEast Pipeline does not have federal court eminent domain authority over lands in which a state has property rights interests. The joint venture is pursuing appellate and other options and is evaluating further next steps. The ultimate outcome of these matters 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, which could result in an impairment of one or both of Southern Company Gas' investments and could have a material impact on Southern Company Gas' and Southern Company's financial statements. Other On May 29, 2019, Southern Company Gas sold its investment in Triton, a cargo container leasing company that was aggregated into Southern Company Gas' all other segment. This disposition resulted in a pre-tax loss of $6 million and a net after-tax gain of $7 million as a result of reversing a $13 million federal income tax valuation allowance.

Financing

Financing	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
FINANCING	FINANCING Bank Credit Arrangements Bank credit arrangements provide liquidity support to the registrants' commercial paper borrowings and the traditional electric operating companies' revenue bonds. The amount of variable rate revenue bonds of the traditional electric operating companies outstanding requiring liquidity support as of September 30, 2019 was approximately $1.4 billion (comprised of approximately $854 million at Alabama Power, $550 million at Georgia Power, and $40 million at Mississippi Power). In addition, at September 30, 2019 , Alabama Power had approximately $87 million of revenue bonds outstanding that were required to be remarketed within the next 12 months. See Note 8 to the financial statements under "Bank Credit Arrangements" in Item 8 of the Form 10-K and " Financing Activities " herein for additional information. The following table outlines the committed credit arrangements by company as of September 30, 2019 : Expires Company 2020 2022 2024 Total Unused Due within One Year (in millions) Southern Company (a) $ — $ — $ 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 — 150 150 — Southern Power (b) — — 600 600 591 — Southern Company Gas (c) — — 1,750 1,750 1,745 — Other 30 — — 30 30 30 Southern Company Consolidated $ 33 $ 675 $ 6,900 $ 7,608 $ 7,576 $ 33 (a) Represents the Southern Company parent entity. (b) Does not include Southern Power Company's $120 million continuing letter of credit facility for standby letters of credit expiring in 2021, of which $30 million was unused at September 30, 2019 . Southern Power's subsidiaries are not parties to its bank credit arrangement. (c) 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 May 2019, Southern Company, Alabama Power, Georgia Power, and Southern Power each amended and restated certain of their multi-year credit arrangements, which, among other things, extended the maturity dates to 2024. Southern Power also decreased its borrowing capacity from $750 million to $600 million . In addition, Southern Company Gas Capital, along with Nicor Gas, amended and restated its multi-year credit arrangement to extend the maturity date to 2024 and decrease the aggregate borrowing capacity from $1.9 billion to $1.75 billion . In June 2019, Mississippi Power entered into a new $50 million credit arrangement that matures in 2022 and amended its existing credit arrangements, which, among other things, extended the maturity dates from 2019 to 2022. In September 2019, Alabama Power amended its $500 million multi-year credit arrangement, which, among other things, extended the maturity date from 2020 to 2022 and increased the borrowing capacity to $525 million . 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. DOE Loan Guarantee Borrowings See Note 8 to the financial statements under "Long-term Debt – DOE Loan Guarantee Borrowings" in Item 8 of the Form 10-K for additional information regarding Georgia Power's 2014 loan guarantee agreement. Pursuant to the loan guarantee program established under Title XVII of the Energy Policy Act of 2005 (Title XVII Loan Guarantee Program), Georgia Power and the DOE entered into a loan guarantee agreement in 2014 and the Amended and Restated Loan Guarantee Agreement in March 2019. Under the Amended and Restated Loan Guarantee Agreement, the DOE has agreed to guarantee the obligations of Georgia Power under note purchase agreements among the DOE, Georgia Power, and the FFB and related promissory notes which provide for two multi-advance term loan facilities (FFB Credit Facilities). Under the FFB Credit Facilities, Georgia Power may make term loan borrowings through the FFB in an amount up to approximately $5.130 billion , provided that total aggregate borrowings under the FFB Credit Facilities may not exceed 70% of (i) Eligible Project Costs minus (ii) approximately $1.492 billion (reflecting the amounts received by Georgia Power under the Guarantee Settlement Agreement less the Customer Refunds). In March 2019, Georgia Power made borrowings under the FFB Credit Facilities in an aggregate principal amount of $835 million at an interest rate of 3.213% through the final maturity date of February 20, 2044. At September 30, 2019 , Georgia Power had a total of $3.46 billion of borrowings outstanding under the FFB Credit Facilities. All borrowings under the FFB Credit Facilities are full recourse to Georgia Power, and Georgia Power is obligated to reimburse the DOE for any payments the DOE is required to make to the FFB under its guarantee. Georgia Power's reimbursement obligations to the DOE are full recourse and secured by a first priority lien on (i) Georgia Power's 45.7% undivided ownership interest in Plant Vogtle Units 3 and 4 (primarily the units under construction, the related real property, and any nuclear fuel loaded in the reactor core) and (ii) Georgia Power's rights and obligations under the principal contracts relating to Plant Vogtle Units 3 and 4. There are no restrictions on Georgia Power's ability to grant liens on other property. In addition to the conditions described above, future advances are subject to satisfaction of customary conditions, as well as certification of compliance with the requirements of the Title XVII Loan Guarantee Program, including accuracy of project-related representations and warranties, delivery of updated project-related information, and evidence of compliance with the prevailing wage requirements of the Davis-Bacon Act of 1931, as amended, and certification from the DOE's consulting engineer that proceeds of the advances are used to reimburse Eligible Project Costs. Upon satisfaction of all conditions described above, advances may be requested on a quarterly basis through 2023. The final maturity date for each advance under the FFB Credit Facilities is February 20, 2044. Interest is payable quarterly and principal payments will begin on February 20, 2020. Borrowings under the FFB Credit Facilities will bear interest at the applicable U.S. Treasury rate plus a spread equal to 0.375% . Under the Amended and Restated Loan Guarantee Agreement, Georgia Power is subject to customary borrower affirmative and negative covenants and events of default. In addition, Georgia Power is subject to project-related reporting requirements and other project-specific covenants and events of default. In the event certain mandatory prepayment events occur, the FFB's commitment to make further advances under the FFB Credit Facilities will terminate and Georgia Power will be required to prepay the outstanding principal amount of all borrowings under the FFB Credit Facilities over a period of five years (with level principal amortization). Among other things, these mandatory prepayment events include (i) the termination of the Vogtle Services Agreement or rejection of the Vogtle Services Agreement in any Westinghouse bankruptcy if Georgia Power does not maintain access to intellectual property rights under the related intellectual property licenses; (ii) termination of the Bechtel Agreement, unless the Vogtle Owners enter into a replacement agreement; (iii) cancellation of Plant Vogtle Units 3 and 4 by the Georgia PSC or by Georgia Power; (iv) failure of the holders of 90% of the ownership interests in Plant Vogtle Units 3 and 4 to vote to continue construction following certain schedule extensions; (v) cost disallowances by the Georgia PSC that could have a material adverse effect on completion of Plant Vogtle Units 3 and 4 or Georgia Power's ability to repay the outstanding borrowings under the FFB Credit Facilities; or (vi) loss of or failure to receive necessary regulatory approvals. Under certain circumstances, insurance proceeds and any proceeds from an event of taking must be applied to immediately prepay outstanding borrowings under the FFB Credit Facilities. In addition, if Georgia Power discontinues construction of Plant Vogtle Units 3 and 4, Georgia Power would be obligated to immediately repay a portion of the outstanding borrowings under the FFB Credit Facilities to the extent such outstanding borrowings exceed 70% of Eligible Project Costs, net of the proceeds received by Georgia Power under the Guarantee Settlement Agreement less the Customer Refunds. Georgia Power also may voluntarily prepay outstanding borrowings under the FFB Credit Facilities. Under the FFB Credit Facilities, any prepayment (whether mandatory or optional) will be made with a make-whole premium or discount, as applicable. In connection with any cancellation of Plant Vogtle Units 3 and 4, the DOE may elect to continue construction of Plant Vogtle Units 3 and 4. In such an event, the DOE will have the right to assume Georgia Power's rights and obligations under the principal agreements relating to Plant Vogtle Units 3 and 4 and to acquire all or a portion of Georgia Power's ownership interest in Plant Vogtle Units 3 and 4. Financing Activities The following table outlines the long-term debt financing activities for Southern Company and its subsidiaries for the first nine months of 2019 : Company Senior Note Issuances Senior Note Maturities, Redemptions, and Repurchases Revenue Bond Issuances and Reofferings of Purchased Bonds Revenue Bond and Other Long-Term Debt Issuances Other Long-Term Debt Redemptions and Maturities (a) (in millions) Southern Company (b) $ — $ 2,400 $ — $ — $ 1,725 $ — Alabama Power 600 200 — — — 1 Georgia Power 750 — 584 223 835 11 Mississippi Power — — 43 — — — Southern Company Gas — 300 — — 200 50 Other — — — 25 — 14 Elimination (c) — — — — — (7 ) Southern Company Consolidated $ 1,350 $ 2,900 $ 627 $ 248 $ 2,760 $ 69 (a) Includes reductions in finance lease obligations resulting from cash payments under finance leases. (b) Represents the Southern Company parent entity. (c) Represents reductions in affiliate finance lease obligations at Georgia Power, which are eliminated in Southern Company's consolidated financial statements. Except as otherwise described herein, Southern Company and its subsidiaries used or will use the proceeds of debt issuances for their redemptions and maturities shown in the table above, to repay short-term indebtedness, and for general corporate purposes, including working capital. The subsidiaries also used or will use the proceeds for their construction programs. Southern Company In January 2019, Southern Company repaid a $250 million short-term uncommitted bank credit arrangement and a $1.5 billion short-term floating rate bank loan. Also in January 2019, through cash tender offers, Southern Company repurchased and retired approximately $522 million of the $1.0 billion aggregate principal amount outstanding of its 1.85% Senior Notes due July 1, 2019 ( 1.85% Notes), approximately $180 million of the $350 million aggregate principal amount outstanding of its Series 2014B 2.15% Senior Notes due September 1, 2019 (Series 2014B Notes), and approximately $504 million of the $750 million aggregate principal amount outstanding of its Series 2018A Floating Rate Notes due February 14, 2020 (Series 2018A Notes), for an aggregate purchase price, excluding accrued and unpaid interest, of approximately $1.2 billion . In addition, following the completion of the cash tender offers, in February 2019, Southern Company completed the redemption of all of the Series 2018A Notes, 1.85% Notes, and Series 2014B Notes remaining outstanding. See " Equity Units " herein for information related to Southern Company's August 2019 issuance of 34.5 million equity units for a total stated amount of $1.725 billion . In September 2019, Southern Company redeemed all $300 million aggregate principal amount of its Series 2017A Floating Rate Senior Notes due September 30, 2020. Alabama Power In September 2019, Alabama Power issued $600 million aggregate principal amount of Series 2019A 3.45% Senior Notes due October 1, 2049. Georgia Power In January 2019, Georgia Power redeemed approximately $13 million , $20 million , and $75 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 1992, Eighth Series 1994, and Second Series 1995, respectively. In March 2019, Georgia Power reoffered to the public the following pollution control revenue bonds that previously had been purchased and held by Georgia Power: • $173 million aggregate principal amount of Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009; • approximately $105 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013; and • $65 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008. In April 2019, Georgia Power purchased and held the following pollution control revenue bonds. In May 2019, Georgia Power reoffered these pollution control revenue bonds to the public. • $55 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994; • $30 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995; • $20 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994; and • $10 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994. In June 2019, Georgia Power reoffered to the public $55 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1994, which previously had been purchased and held by Georgia Power. Also in June 2019, Georgia Power entered into two short-term floating rate bank loans in aggregate principal amounts of $125 million each, both of which bear interest based on one-month LIBOR. In August 2019, Georgia Power reoffered to the public approximately $72 million aggregate principal amount of Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2013, which previously had been purchased and held by Georgia Power. In September 2019, Georgia Power issued $400 million aggregate principal amount of Series 2019A 2.20% Senior Notes due September 15, 2024 and $350 million aggregate principal amount of Series 2019B 2.65% Senior Notes due September 15, 2029. Mississippi Power In March 2019, Mississippi Power reoffered to the public $43 million of Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002, which previously had been purchased and held by Mississippi Power. Southern Power In May 2019, Southern Power repaid at maturity a $100 million aggregate principal amount short-term bank loan. Southern Company Gas In August 2019, Nicor Gas issued $200 million aggregate principal amount of first mortgage bonds in a private placement. Nicor Gas entered into an agreement to issue an additional $100 million aggregate principal amount of first mortgage bonds on October 30, 2019. Equity Units In August 2019, Southern Company issued 34.5 million 2019 Series A Equity Units (Equity Units), initially in the form of corporate units (Corporate Units), at a stated amount of $50 per Corporate Unit, for a total stated amount of $1.725 billion . Net proceeds from the issuance were approximately $1.682 billion . The proceeds were used to repay short-term indebtedness and for other general corporate purposes, including investments in Southern Company's subsidiaries. Each Corporate Unit is comprised of (i) a 1 / 40 undivided beneficial ownership interest in $1,000 principal amount of Southern Company's Series 2019A Remarketable Junior Subordinated Notes (Series 2019A RSNs) due 2024, (ii) a 1 / 40 undivided beneficial ownership interest in $1,000 principal amount of Southern Company's Series 2019B Remarketable Junior Subordinated Notes (together with the Series 2019A RSNs, the RSNs) due 2027, and (iii) a stock purchase contract, which obligates the holder to purchase from Southern Company, no later than August 1, 2022, a certain number of shares of Southern Company's common stock for $50 in cash (Stock Purchase Contract). Southern Company has agreed to remarket the RSNs in 2022, at which time each interest rate on the RSNs will reset at the applicable market rate. Holders may choose to either remarket their RSNs, receive the proceeds, and use those funds to settle the related Stock Purchase Contract or retain the RSNs and use other funds to settle the related Stock Purchase Contract. If the remarketing is unsuccessful, holders will have the right to put their RSNs to Southern Company at a price equal to the principal amount. The Corporate Units carry an annual distribution rate of 6.75% of the stated amount, which is comprised of a quarterly interest payment on the RSNs of 2.70% per year and a quarterly purchase contract adjustment payment of 4.05% per year. Each Stock Purchase Contract obligates the holder to purchase, and Southern Company to sell, for $50 a number of shares of Southern Company common stock determined based on the applicable market value (as determined under the related Stock Purchase Contract) in accordance with the conversion ratios set forth below (subject to anti-dilution adjustments): • If the applicable market value is equal to or greater than $68.64 , 0.7284 shares. • If the applicable market value is less than $68.64 but greater than $57.20 , a number of shares equal to $50 divided by the applicable market value. • If the applicable market value is less than or equal to $57.20 , 0.8741 shares. A holder's ownership interest in the RSNs is pledged to Southern Company to secure the holder's obligation under the related Stock Purchase Contract. If a holder of a Stock Purchase Contract chooses at any time to have its RSNs released from the pledge, such holder's obligation under such Stock Purchase Contract must be secured by a U.S. Treasury security equal to the aggregate principal amount of the RSNs. At the time of issuance, the RSNs were recorded on Southern Company's consolidated balance sheet as long-term debt and the present value of the contract adjustment payments of $198 million was recorded as a liability (of which $63 million was classified as current at September 30, 2019 ), representing the obligation to make contract adjustment payments, with an offsetting reduction to paid-in capital. The difference between the face value and present value of the contract adjustment payments will be accreted to interest expense on the consolidated statements of income over the three-year period ending in 2022. The liability recorded for the contract adjustment payments is considered non-cash and excluded from the consolidated statements of cash flows. To settle the Stock Purchase Contracts, Southern Company will be required to issue a maximum of 30.2 million shares of common stock (subject to anti-dilution adjustments and a make-whole adjustment if certain fundamental changes occur). Earnings per Share For Southern Company, the only difference in computing basic and diluted earnings per share is attributable to awards outstanding under stock-based compensation plans and the Equity Units. Earnings per share dilution resulting from stock-based compensation plans and the Equity Units issuance is determined under the treasury stock method. See " Equity Units " herein for additional information and Note 12 to the financial statements in Item 8 of the Form 10-K for information on stock-based compensation plans. Shares used to compute diluted earnings per share were as follows: Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) As reported shares 1,048 1,023 1,043 1,016 Effect of stock-based compensation 9 6 8 5 Diluted shares 1,057 1,029 1,051 1,021 There were no stock-based compensation awards that were not included in the diluted earnings per share calculation because they were anti-dilutive for the three and nine months ended September 30, 2019 and an immaterial amount of such awards was not included for the three and nine months ended September 30, 2018 . The Equity Units issued in August 2019 were excluded from the calculation of diluted earnings per share for the three and nine months ended September 30, 2019 as the dilutive stock price threshold was not met.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
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 Carryforwards Southern Company had federal ITC and PTC carryforwards (primarily related to Southern Power) totaling $1.8 billion as of September 30, 2019 compared to $2.4 billion as of December 31, 2018. The federal ITC and PTC carryforwards begin expiring in 2034 and 2032, respectively, but are expected to be fully utilized by 2023. The estimated tax credit utilization reflects the projected taxable gains on the various sale transactions describe in Note (K) and could be further delayed 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, 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 regarding 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 and 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 30.2% for the nine months ended September 30, 2019 compared to 22.7% for the corresponding period in 2018 . The effective tax rate increase was primarily due to the tax impact from the sale of Gulf Power in 2019 and the reductions of tax benefits associated with wind PTCs following Southern Power's 2018 sale of a noncontrolling tax equity interest in its wind projects. The effective tax rate increase was partially offset by the tax impacts related to the Southern Company Gas Dispositions in 2018. See Note (K) for additional information. Georgia Power Georgia Power's effective tax rate was 22.6% for the nine months ended September 30, 2019 compared to 25.5% for the corresponding period in 2018. The effective tax rate decrease was primarily due to an increase in state ITCs in 2019 related to the construction of Plant Vogtle Units 3 and 4 and the impact of recording a valuation allowance on certain state tax credit carryforwards in 2018, partially offset by additional benefits recorded in 2018 as a result of the Tax Reform Legislation. Mississippi Power Mississippi Power's effective tax rate was 16.3% for the nine months ended September 30, 2019 compared to 20.8% for the corresponding period in 2018 . The effective tax rate decrease was primarily due to an increase in the flowback of excess deferred income taxes as a result of both a settlement agreement reached with wholesale customers under the MRA tariff and a new tolling arrangement accounted for as a sales-type lease. See Note (B) under "Mississippi Power" for additional information on the settlement agreement. Southern Power Southern Power's effective tax benefit rate was (13.6)% for the nine months ended September 30, 2019 compared to (220.3)% for the corresponding period in 2018 . The effective tax benefit rate decrease primarily resulted from lower wind PTCs following the 2018 sale of a noncontrolling tax equity interest in SP Wind and changes in state apportionment rates following the 2018 reorganization of certain legal entities, partially offset by the net tax benefits from the sale of Plant Nacogdoches in 2019. See Note (K) and Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Power" for additional information. Southern Company Gas Southern Company Gas' effective tax rate was 15.0% for the nine months ended September 30, 2019 compared to 61.8% for the corresponding period in 2018 . This decrease was primarily related to an increase in the flowback of excess deferred income taxes in 2019, primarily at Atlanta Gas Light as previously authorized by the Georgia PSC, and the reversal of a federal tax valuation allowance in connection with Southern Company Gas' sale of Triton in 2019, as well as the tax impacts of the Southern Company Gas Dispositions in 2018. See Note (E) under "Southern Company Gas" and Notes 2 and 15 to the financial statements under "Southern Company Gas" in Item 8 of the Form 10-K for additional information.

Retirement Benefits

Retirement Benefits	9 Months Ended
	Sep. 30, 2019
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, 2019 . The Southern Company system also provides certain non-qualified defined benefits for a select group of management and highly compensated employees, which are funded on a cash basis. In addition, the Southern Company system provides certain medical care and life insurance benefits for retired employees through other postretirement benefit plans. The traditional electric operating companies fund other postretirement trusts to the extent required by their respective regulatory commissions. Southern Company Gas has a separate unfunded supplemental retirement health care plan that provides medical care and life insurance benefits to employees of discontinued businesses. See Note 11 to the financial statements in Item 8 of the Form 10-K for additional information. On each registrant's condensed statements of income, the service cost component of net periodic benefit costs is included in other operations and maintenance expenses and all other components of net periodic benefit costs are included in other income (expense), net. Components of the net periodic benefit costs for the three and nine months ended September 30, 2019 and 2018 are presented in the following tables. Three Months Ended September 30, 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 $ 7 Interest cost 123 28 38 6 1 9 Expected return on plan assets (222 ) (51 ) (73 ) (10 ) (2 ) (15 ) Amortization: Prior service costs 1 — — — — (1 ) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (5 ) $ — $ 1 $ 4 Postretirement Benefits Service cost $ 5 $ 1 $ 2 $ 1 $ — $ — Interest cost 18 4 6 — — 2 Expected return on plan assets (16 ) (6 ) (7 ) — — (1 ) Amortization: Prior service costs — 1 — — — — Regulatory asset — — — — — 1 Net (gain)/loss (1 ) — 1 — — — Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2 Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 219 $ 51 $ 56 $ 9 $ 5 $ 19 Interest cost 369 85 116 17 4 27 Expected return on plan assets (664 ) (154 ) (219 ) (30 ) (7 ) (45 ) Amortization: Prior service costs 2 1 1 — — (2 ) Regulatory asset — — — — — 10 Net (gain)/loss 90 27 33 4 — 2 Net periodic pension cost (income) $ 16 $ 10 $ (13 ) $ — $ 2 $ 11 Postretirement Benefits Service cost $ 14 $ 3 $ 4 $ 1 $ — $ 1 Interest cost 52 12 19 2 — 7 Expected return on plan assets (49 ) (19 ) (19 ) (1 ) — (4 ) Amortization: Prior service costs 2 3 — — — — Regulatory asset — — — — — 4 Net (gain)/loss (2 ) — 1 — — (2 ) Net periodic postretirement benefit cost $ 17 $ (1 ) $ 5 $ 2 $ — $ 6 Three Months Ended September 30, 2018 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 90 $ 19 $ 22 $ 5 $ 3 $ 8 Interest cost 116 26 34 5 1 10 Expected return on plan assets (236 ) (51 ) (74 ) (11 ) (3 ) (18 ) Amortization: Prior service costs 1 — 1 — — (1 ) Regulatory asset — — — — — 4 Net (gain)/loss 53 13 18 3 — 3 Net periodic pension cost (income) $ 24 $ 7 $ 1 $ 2 $ 1 $ 6 Postretirement Benefits Service cost $ 6 $ 1 $ 2 $ — $ 1 $ — Interest cost 19 5 7 — — 2 Expected return on plan assets (17 ) (7 ) (6 ) — — (1 ) Amortization: Prior service costs 2 1 — — — — Regulatory asset — — — — — 2 Net (gain)/loss 3 — 2 — — — Net periodic postretirement benefit cost $ 13 $ — $ 5 $ — $ 1 $ 3 Nine Months Ended September 30, 2018 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 269 $ 58 $ 65 $ 13 $ 7 $ 24 Interest cost 348 76 104 15 4 29 Expected return on plan assets (707 ) (155 ) (222 ) (31 ) (8 ) (53 ) Amortization: Prior service costs 3 1 2 — — (2 ) Regulatory asset — — — — — 11 Net (gain)/loss 160 40 52 8 1 9 Net periodic pension cost (income) $ 73 $ 20 $ 1 $ 5 $ 4 $ 18 Postretirement Benefits Service cost $ 18 $ 4 $ 5 $ 1 $ 1 $ 1 Interest cost 56 13 21 2 — 7 Expected return on plan assets (51 ) (20 ) (19 ) (1 ) — (5 ) Amortization: Prior service costs 5 3 1 — — — Regulatory asset — — — — — 5 Net (gain)/loss 10 1 6 — — — Net periodic postretirement benefit cost $ 38 $ 1 $ 14 $ 2 $ 1 $ 8

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS As of September 30, 2019 , assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows: Fair Value Measurements Using: As of September 30, 2019: 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) $ 297 $ 156 $ 34 $ — $ 487 Interest rate derivatives — 2 — — 2 Investments in trusts: (b)(c) Domestic equity 713 126 — — 839 Foreign equity 61 204 — — 265 U.S. Treasury and government agency securities — 301 — — 301 Municipal bonds — 86 — — 86 Pooled funds – fixed income — 16 — — 16 Corporate bonds 24 306 — — 330 Mortgage and asset backed securities — 82 — — 82 Private equity — — — 53 53 Cash and cash equivalents 1 — — — 1 Other 17 6 — — 23 Cash equivalents 2,078 7 — — 2,085 Other investments 9 15 — — 24 Total $ 3,200 $ 1,307 $ 34 $ 53 $ 4,594 Liabilities: Energy-related derivatives (a) $ 412 $ 227 $ 28 $ — $ 667 Interest rate derivatives — 72 — — 72 Foreign currency derivatives — 32 — — 32 Contingent consideration — — 21 — 21 Total $ 412 $ 331 $ 49 $ — $ 792 Fair Value Measurements Using: As of September 30, 2019: 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 464 114 — — 578 Foreign equity 61 60 — — 121 U.S. Treasury and government agency securities — 23 — — 23 Municipal bonds — 1 — — 1 Corporate bonds 24 142 — — 166 Mortgage and asset backed securities — 26 — — 26 Private equity — — — 53 53 Other 5 — — — 5 Cash equivalents 1,136 7 — — 1,143 Other investments 15 — — 15 Total $ 1,690 $ 393 $ — $ 53 $ 2,136 Liabilities: Energy-related derivatives $ — $ 22 $ — $ — $ 22 Georgia Power Assets: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Nuclear decommissioning trusts: (b)(c) Domestic equity 248 1 — — 249 Foreign equity — 140 — — 140 U.S. Treasury and government agency securities — 277 — — 277 Municipal bonds — 86 — — 86 Corporate bonds — 164 — — 164 Mortgage and asset backed securities — 55 — — 55 Other 12 6 — — 18 Cash equivalents 392 — — — 392 Total $ 652 $ 732 $ — $ — $ 1,384 Liabilities: Energy-related derivatives $ — $ 49 $ — $ — $ 49 Interest rate derivatives — 60 — — 60 Total $ — $ 109 $ — $ — $ 109 Fair Value Measurements Using: As of September 30, 2019: 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 $ — $ 2 $ — $ — $ 2 Cash equivalents 234 — — — 234 Total $ 234 $ 2 $ — $ — $ 236 Liabilities: Energy-related derivatives $ — $ 24 $ — $ — $ 24 Southern Power Assets: Cash equivalents $ 23 $ — $ — $ — $ 23 Liabilities: Energy-related derivatives $ — $ 4 $ — $ — $ 4 Foreign currency derivatives — 32 — — 32 Contingent consideration — — 21 — 21 Total $ — $ 36 $ 21 $ — $ 57 Southern Company Gas Assets: Energy-related derivatives (a) $ 297 $ 146 $ 34 $ — $ 477 Non-qualified deferred compensation trusts: Domestic equity — 11 — — 11 Foreign equity — 4 — — 4 Pooled funds – fixed income — 16 — — 16 Cash equivalents 1 — — — 1 Total $ 298 $ 177 $ 34 $ — $ 509 Liabilities: Energy-related derivatives (a) $ 412 $ 128 $ 28 $ — $ 568 Interest rate derivatives — 5 — — 5 Total $ 412 $ 133 $ 28 $ — $ 573 (a) Energy-related derivatives exclude cash collateral of $166 million . (b) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. (c) Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of September 30, 2019 , approximately $50 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan to creditors under the funds' managers' securities lending program. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. Southern Company, Alabama Power, and Georgia Power continue to elect the option to fair value investment securities held in the nuclear decommissioning trust funds. The fair value of the funds, including reinvested interest and dividends and excluding the funds' expenses, increased (decreased) by the amounts shown in the table below for the three and nine months ended September 30, 2019 and 2018. The changes were recorded as a change to the regulatory assets and liabilities related to AROs for Georgia Power and Alabama Power, respectively. Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) Southern Company $ 27 $ 58 $ 255 $ 68 Alabama Power 15 39 140 49 Georgia Power 12 19 115 19 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. As of September 30, 2019 , 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 $53 million and unfunded commitments related to the private equity investments totaled $54 million . Private equity funds include funds-of-funds that invest in high-quality private equity funds across several market sectors, funds that invest in real estate assets, and a fund that acquires companies to create resale value. Private equity funds do not have redemption rights. Distributions from these funds will be received as the underlying investments in the funds are liquidated. As of September 30, 2019 , 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 $ 45,182 $ 8,516 $ 11,787 $ 1,616 $ 4,960 $ 5,755 Fair value 49,424 9,646 13,001 1,717 5,290 6,489 (*) 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 Southern Company, Alabama Power, Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas. Commodity Contracts with Level 3 Valuation Inputs As of September 30, 2019 , the fair value of Southern Company Gas' Level 3 physical natural gas forward contracts was $5 million . Since commodity contracts classified as Level 3 typically include a combination of observable and unobservable components, the changes in fair value may include amounts due in part to observable market factors, or changes to assumptions on the unobservable components. The following table includes transfers to Level 3, which represent the fair value of Southern Company Gas' commodity derivative contracts that include a significant unobservable component for the first time during the period. Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 (in millions) Beginning balance $ (10 ) $ — Transfers to Level 3 — (33 ) Transfers from Level 3 3 3 Instruments realized or otherwise settled during period (2 ) (2 ) Changes in fair value 14 37 Ending balance $ 5 $ 5 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 $(0.05) to $0.74 per mmBtu). Forward price increases (decreases) as of September 30, 2019 would have resulted in higher (lower) values on a net basis.

Derivatives

Derivatives	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	DERIVATIVES Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas are exposed to market risks, including commodity price risk, interest rate risk, weather risk, and occasionally foreign currency exchange rate risk. To manage the volatility attributable to these exposures, each company nets its exposures, where possible, to take advantage of natural offsets and enters into various derivative transactions for the remaining exposures pursuant to each company's policies in areas such as counterparty exposure and risk management practices. Southern Company Gas' wholesale gas operations use various contracts in its commercial activities that generally meet the definition of derivatives. For the traditional electric operating companies, Southern Power, and Southern Company Gas' other businesses, each company's policy is that derivatives are to be used primarily for hedging purposes and mandates strict adherence to all applicable risk management policies. Derivative positions are monitored using techniques including, but not limited to, market valuation, value at risk, stress testing, and sensitivity analysis. Derivative instruments are recognized at fair value in the balance sheets as either assets or liabilities and are presented on a net basis. See Note (I) for additional fair value information. In the statements of cash flows, any cash impacts of settled energy-related and interest rate derivatives are recorded as operating activities. Any cash impacts of settled foreign currency derivatives are classified as operating or financing activities to correspond with classification of the hedged interest or principal, respectively. See Note 1 to the financial statements under "Financial Instruments" in Item 8 of the Form 10-K for additional information. Energy-Related Derivatives The traditional electric operating companies, Southern Power, and Southern Company Gas enter into energy-related derivatives to hedge exposures to electricity, natural gas, and other fuel price changes. However, due to cost-based rate regulations and other various cost recovery mechanisms, the traditional electric operating companies and the natural gas distribution utilities have limited exposure to market volatility in energy-related commodity prices. Each of the traditional electric operating companies and certain of the natural gas distribution utilities of Southern Company Gas manage fuel-hedging programs, implemented per the guidelines of their respective state PSCs or other applicable state regulatory agencies, through the use of financial derivative contracts, which are expected to continue to mitigate price volatility. The traditional electric operating companies (with respect to wholesale generating capacity) and Southern Power have limited exposure to market volatility in energy-related commodity prices because their long-term sales contracts shift substantially all fuel cost responsibility to the purchaser. However, the traditional electric operating companies and Southern Power may be exposed to market volatility in energy-related commodity prices to the extent any uncontracted capacity is used to sell electricity. Southern Company Gas retains exposure to price changes that can, in a volatile energy market, be material and can adversely affect its results of operations. Southern Company Gas also enters into weather derivative contracts as economic hedges of operating margins in the event of warmer-than-normal weather. Exchange-traded options are carried at fair value, with changes reflected in operating revenues. Non-exchange-traded options are accounted for using the intrinsic value method. Changes in the intrinsic value for non-exchange-traded contracts are reflected in operating revenues. Energy-related derivative contracts are accounted for under one of three methods: • Regulatory Hedges — Energy-related derivative contracts designated as regulatory hedges relate primarily to the traditional electric operating companies' and the natural gas distribution utilities' fuel-hedging programs, where gains and losses are initially recorded as regulatory liabilities and assets, respectively, and then are included in fuel expense as the underlying fuel is used in operations and ultimately recovered through the respective fuel cost recovery clauses. • Cash Flow Hedges — Gains and losses on energy-related derivatives designated as cash flow hedges (which are mainly used to hedge anticipated purchases and sales) are initially deferred in accumulated OCI before being recognized in the statements of income in the same period and in the same income statement line item as the earnings effect of the hedged transactions. • Not Designated — Gains and losses on energy-related derivative contracts that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. Some energy-related derivative contracts require physical delivery as opposed to financial settlement, and this type of derivative is both common and prevalent within the electric and natural gas industries. When an energy-related derivative contract is settled physically, any cumulative unrealized gain or loss is reversed and the contract price is recognized in the respective line item representing the actual price of the underlying goods being delivered. At September 30, 2019 , 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 (*) 475 2023 2029 Alabama Power 89 2022 — Georgia Power 184 2023 — Mississippi Power 99 2023 — Southern Power 9 2020 — Southern Company Gas (*) 94 2022 2029 (*) 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 4.1 billion mmBtu and short natural gas positions of 4.1 billion mmBtu as of September 30, 2019 , which is also included in Southern Company's total volume. 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 25 million mmBtu for Southern Company, which includes 4 million mmBtu for Alabama Power, 8 million mmBtu for Georgia Power, 4 million mmBtu for Mississippi Power, and 9 million mmBtu for Southern Power. For cash flow hedges of energy-related derivatives, the estimated pre-tax gains (losses) expected to be reclassified from accumulated OCI to earnings for the 12 -month period ending September 30, 2020 are immaterial for all registrants. Interest Rate Derivatives Southern Company and certain subsidiaries may enter into interest rate derivatives to hedge exposure to changes in interest rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. Derivatives related to existing variable rate securities or forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and presented on the same income statement line item as the earnings effect of the hedged transactions. Derivatives related to existing fixed rate securities are accounted for as fair value hedges, where the derivatives' fair value gains or losses and hedged items' fair value gains or losses are both recorded directly to earnings on the same income statement line item. Fair value gains or losses on derivatives that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. At September 30, 2019 , 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 September 30, 2019 (in millions) (in millions) Cash Flow Hedges of Forecasted Debt Georgia Power $ 250 3-month LIBOR 2.23% March 2025 $ (9 ) Georgia Power 250 3-month LIBOR 2.40% March 2030 (20 ) Georgia Power 250 3-month LIBOR 2.48% February 2044 (30 ) Southern Company Gas 200 3-month LIBOR 1.81% September 2030 (5 ) Fair Value Hedges of Existing Debt Southern Company (*) 300 2.75% 3-month LIBOR+0.92% June 2020 (1 ) Southern Company (*) 1,500 2.35% 1-month LIBOR+0.87% July 2021 (5 ) Georgia Power 200 4.25% 3-month LIBOR+2.46% December 2019 (1 ) Southern Company Consolidated $ 2,950 $ (71 ) (*) Represents the Southern Company parent entity. 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 September 30, 2020 total $(21) million for Southern Company and are immaterial for all other registrants. Deferred gains and losses related to interest rate derivatives are expected to be amortized into earnings through 2046 for the Southern Company parent entity, 2035 for Alabama Power, 2044 for Georgia Power, 2028 for Mississippi Power, and 2046 for Southern Company Gas. Foreign Currency Derivatives Southern Company and certain subsidiaries, including Southern Power, may enter into foreign currency derivatives to hedge exposure to changes in foreign currency exchange rates, such as that arising from the issuance of debt denominated in a currency other than U.S. dollars. Derivatives related to forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and on the same income statement line as the earnings effect of the hedged transactions, including foreign currency gains or losses arising from changes in the U.S. currency exchange rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. At September 30, 2019 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at September 30, 2019 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ (21 ) Southern Power 564 3.78% 500 1.85% June 2026 (11 ) Total $ 1,241 € 1,100 $ (32 ) The estimated pre-tax gains (losses) related to Southern Power's foreign currency derivatives expected to be reclassified from accumulated OCI to earnings for the 12 -month period ending September 30, 2020 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 September 30, 2019 As of December 31, 2018 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 $ 5 $ 61 $ 8 $ 23 Other deferred charges and assets/Other deferred credits and liabilities 6 44 9 26 Assets held for sale, current/Liabilities held for sale, current — 6 Total derivatives designated as hedging instruments for regulatory purposes $ 11 $ 105 $ 17 $ 55 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ — $ 8 $ 3 $ 7 Other deferred charges and assets/Other deferred credits and liabilities — 1 1 2 Interest rate derivatives: Other current assets/Other current liabilities — 72 — 19 Other deferred charges and assets/Other deferred credits and liabilities 2 — — 30 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 23 Other deferred charges and assets/Other deferred credits and liabilities — 8 75 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 2 $ 113 $ 79 $ 81 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 311 $ 342 $ 561 $ 575 Other deferred charges and assets/Other deferred credits and liabilities 165 211 180 325 Total derivatives not designated as hedging instruments $ 476 $ 553 $ 741 $ 900 Gross amounts recognized $ 489 $ 771 $ 837 $ 1,036 Gross amounts offset (a) $ (348 ) $ (514 ) $ (524 ) $ (801 ) Net amounts recognized in the Balance Sheets (b) $ 141 $ 257 $ 313 $ 235 As of September 30, 2019 As of December 31, 2018 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 $ 12 $ 3 $ 4 Other deferred charges and assets/Other deferred credits and liabilities 2 10 3 6 Total derivatives designated as hedging instruments for regulatory purposes $ 5 $ 22 $ 6 $ 10 Gross amounts recognized $ 5 $ 22 $ 6 $ 10 Gross amounts offset $ (2 ) $ (2 ) $ (4 ) $ (4 ) Net amounts recognized in the Balance Sheets $ 3 $ 20 $ 2 $ 6 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 27 $ 2 $ 8 Other deferred charges and assets/Other deferred credits and liabilities 2 22 4 13 Total derivatives designated as hedging instruments for regulatory purposes $ 3 $ 49 $ 6 $ 21 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ — $ 60 $ — $ 2 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 60 $ — $ 2 Gross amounts recognized $ 3 $ 109 $ 6 $ 23 Gross amounts offset $ (3 ) $ (3 ) $ (6 ) $ (6 ) Net amounts recognized in the Balance Sheets $ — $ 106 $ — $ 17 As of September 30, 2019 As of December 31, 2018 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 $ — $ 12 $ 1 $ 3 Other deferred charges and assets/Other deferred credits and liabilities 2 12 2 6 Total derivatives designated as hedging instruments for regulatory purposes $ 2 $ 24 $ 3 $ 9 Gross amounts recognized $ 2 $ 24 $ 3 $ 9 Gross amounts offset $ (2 ) $ (2 ) $ (2 ) $ (2 ) Net amounts recognized in the Balance Sheets $ — $ 22 $ 1 $ 7 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ — $ 4 $ 3 $ 6 Other deferred charges and assets/Other deferred credits and liabilities — — 1 2 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 23 Other deferred charges and assets/Other deferred credits and liabilities — 8 75 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 36 $ 79 $ 31 Gross amounts recognized $ — $ 36 $ 79 $ 31 Gross amounts offset $ — $ — $ (3 ) $ (3 ) Net amounts recognized in the Balance Sheets $ — $ 36 $ 76 $ 28 As of September 30, 2019 As of December 31, 2018 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 $ 1 $ 10 $ 2 $ 8 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 10 $ 2 $ 9 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ — $ 4 $ — $ 1 Other deferred charges and assets/Other deferred credits and liabilities — 1 — — Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — 5 — — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 10 $ — $ 1 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 311 $ 342 $ 559 $ 574 Other deferred charges and assets/Other deferred credits and liabilities 165 211 180 325 Total derivatives not designated as hedging instruments $ 476 $ 553 $ 739 $ 899 Gross amounts of recognized $ 477 $ 573 $ 741 $ 909 Gross amounts offset (a) $ (341 ) $ (507 ) $ (508 ) $ (785 ) Net amounts recognized in the Balance Sheets (b) $ 136 $ 66 $ 233 $ 124 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $166 million and $277 million as of September 30, 2019 and December 31, 2018 , respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $8 million as of December 31, 2018 . At September 30, 2019 and December 31, 2018 , 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 September 30, 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 $ (55 ) $ (11 ) $ (27 ) $ (12 ) $ (5 ) Other regulatory assets, deferred (37 ) (8 ) (19 ) (10 ) — Other regulatory liabilities, current 6 3 — — 3 Total energy-related derivative gains (losses) $ (86 ) $ (16 ) $ (46 ) $ (22 ) $ (2 ) (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $8 million at September 30, 2019 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2018 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 $ (19 ) $ (3 ) $ (6 ) $ (2 ) $ (8 ) Other regulatory assets, deferred (16 ) (3 ) (9 ) (4 ) — Assets held for sale, current (6 ) — — — — Other regulatory liabilities, current 1 — — — 1 Total energy-related derivative gains (losses) $ (40 ) $ (6 ) $ (15 ) $ (6 ) $ (7 ) For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of cash flow hedge accounting on accumulated OCI were as follows: Gain (Loss) Recognized in OCI on Derivative For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) (in millions) Southern Company Energy-related derivatives $ (5 ) $ (5 ) $ (11 ) $ 7 Interest rate derivatives (52 ) — (88 ) (2 ) Foreign currency derivatives (68 ) (10 ) (107 ) (31 ) Total $ (125 ) $ (15 ) $ (206 ) $ (26 ) Georgia Power Interest rate derivatives $ (47 ) $ — $ (83 ) $ — Total $ (47 ) $ — $ (83 ) $ — Southern Power Energy-related derivatives $ (3 ) $ (5 ) $ (5 ) $ 5 Foreign currency derivatives (68 ) (10 ) (107 ) (31 ) Total $ (71 ) $ (15 ) $ (112 ) $ (26 ) For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of energy-related derivatives and interest rate derivatives designated as cash flow hedging instruments on accumulated OCI were immaterial for the other registrants. For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of cash flow and fair value hedge accounting on income were as follows: Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) (in millions) Southern Company Total depreciation and amortization $ 760 $ 787 $ 2,267 $ 2,338 Gain (loss) on energy-related cash flow hedges (a) (1 ) — (5 ) 2 Total interest expense, net of amounts capitalized (434 ) (458 ) (1,294 ) (1,386 ) Gain (loss) on interest rate cash flow hedges (a) (5 ) (5 ) (14 ) (16 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) (18 ) (18 ) Gain (loss) on interest rate fair value hedges (b) 10 (4 ) 43 (35 ) Total other income (expense), net 61 57 239 195 Gain (loss) on foreign currency cash flow hedges (a)(c) (54 ) (9 ) (62 ) (46 ) Southern Power Total depreciation and amortization $ 120 $ 130 $ 357 $ 370 Gain (loss) on energy-related cash flow hedges (a) (1 ) — (5 ) 2 Total interest expense, net of amounts capitalized (43 ) (45 ) (127 ) (138 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) (18 ) (18 ) Total other income (expense), net 6 17 48 22 Gain (loss) on foreign currency cash flow hedges (a)(c) (54 ) (9 ) (62 ) (46 ) (a) Reclassified from accumulated OCI into earnings. (b) For fair value hedges, changes in the fair value of the derivative contracts are generally equal to changes in the fair value of the underlying debt and have no material impact on income. (c) The reclassification from accumulated OCI into other income (expense), net completely offsets currency gains and losses arising from changes in the U.S. currency exchange rates used to record the euro-denominated notes. For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of cash flow and fair value hedge accounting on income for energy-related derivatives and interest rate derivatives were immaterial for the traditional electric operating companies and Southern Company Gas. As of September 30, 2019 and December 31, 2018, the following amounts were recorded on the balance sheets related to cumulative basis adjustments for fair value hedges: Carrying Amount of the Hedged Item Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item Balance Sheet Location of Hedged Items As of September 30, 2019 As of December 31, 2018 As of September 30, 2019 As of December 31, 2018 (in millions) (in millions) Southern Company Securities due within one year $ (500 ) $ (498 ) $ — $ 2 Long-term debt (2,093 ) (2,052 ) (2 ) 41 Georgia Power Securities due within one year $ (500 ) $ (498 ) $ — $ 2 For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of energy-related derivatives not designated as hedging instruments on the statements of income of Southern Company and Southern Company Gas were as follows: Gain (Loss) Three Months Ended September 30, Nine Months Ended September 30, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2019 2018 2019 2018 (in millions) (in millions) Energy-related derivatives: Natural gas revenues (*) $ (2 ) $ (36 ) $ 81 $ (79 ) Cost of natural gas 2 2 5 5 Total derivatives in non-designated hedging relationships $ — $ (34 ) $ 86 $ (74 ) (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented. For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of energy-related derivatives and interest rate derivatives not designated as hedging instruments were immaterial for the traditional electric operating companies and Southern Power. Contingent Features Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas do not have any credit arrangements that would require material changes in payment schedules or terminations as a result of a credit rating downgrade. There are certain derivatives that could require collateral, but not accelerated payment, in the event of various credit rating changes of certain Southern Company subsidiaries. At September 30, 2019 , the registrants had no collateral posted with derivative counterparties to satisfy these arrangements. For the registrants with interest rate derivatives at September 30, 2019 , the fair value of interest rate derivative liabilities with contingent features and the maximum potential collateral requirements arising from the credit-risk-related contingent features, at a rating below BBB- and/or Baa3, was immaterial. At September 30, 2019 , the fair value of energy-related derivative liabilities with contingent features and the maximum potential collateral requirements arising from the credit-risk-related contingent features, at a rating below BBB- and/or Baa3, were immaterial for all registrants. The maximum potential collateral requirements arising from the credit-risk-related contingent features for the traditional electric operating companies and Southern Power include certain agreements that could require collateral in the event that one or more Southern Company power pool participants has a credit rating change to below investment grade. Following the sale of Gulf Power to NextEra Energy, Gulf Power is continuing to participate in the Southern Company power pool for a defined transition period that, subject to certain potential adjustments, is scheduled to end on January 1, 2024. Generally, collateral may be provided by a Southern Company guaranty, letter of credit, or cash. If collateral is required, fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral are not offset against fair value amounts recognized for derivatives executed with the same counterparty. Alabama Power and Southern Power maintain accounts with certain regional transmission organizations to facilitate financial derivative transactions. Based on the value of the positions in these accounts and the associated margin requirements, Alabama Power and Southern Power may be required to post collateral. At September 30, 2019 , cash collateral posted in these accounts was immaterial. Southern Company Gas maintains accounts with brokers or the clearing houses of certain exchanges to facilitate financial derivative transactions. Based on the value of the positions in these accounts and the associated margin requirements, Southern Company Gas may be required to deposit cash into these accounts. At September 30, 2019 , cash collateral held on deposit in broker margin accounts was $166 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 Inc. ratings, commercially available credit reports, and audited financial statements. Southern Company Gas may require counterparties to pledge additional collateral when deemed necessary. In addition, Southern Company Gas conducts credit evaluations and obtains appropriate internal approvals for the counterparty's line of credit before any transaction with the counterparty is executed. In most cases, the counterparty must have an investment grade rating, which includes a minimum long-term debt rating of Baa3 from Moody's and BBB- from S&P. Generally, Southern Company Gas requires credit enhancements by way of a guaranty, cash deposit, or letter of credit for transaction counterparties that do not have investment grade ratings. Southern Company Gas also utilizes master netting agreements whenever possible to mitigate exposure to counterparty credit risk. When Southern Company Gas is engaged in more than one outstanding derivative transaction with the same counterparty and it also has a legally enforceable netting agreement with that counterparty, the "net" mark-to-market exposure represents the netting of the positive and negative exposures with that counterparty and a reasonable measure of Southern Company Gas' credit risk. Southern Company Gas also uses other netting agreements with certain counterparties with whom it conducts significant transactions. Master netting agreements enable Southern Company Gas to net certain assets and liabilities by counterparty. Southern Company Gas also nets across product lines and against cash collateral provided the master netting and cash collateral agreements include such provisions. Southern Company Gas may require counterparties to pledge additional collateral when deemed necessary. The registrants do not anticipate a material adverse effect on their respective financial statements as a result of counterparty nonperformance.

Acquisitions and Dispositions

Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2019
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. Southern Company On January 1, 2019, Southern Company completed the sale of all of the capital stock of Gulf Power to 700 Universe, LLC, a wholly-owned subsidiary of NextEra Energy, for an aggregate cash purchase price of approximately $5.8 billion (less $1.3 billion of indebtedness assumed), subject to customary working capital adjustments. The preliminary gain associated with the sale of Gulf Power totaled $2.5 billion pre-tax ( $1.3 billion after tax). The assets and liabilities of Gulf Power were classified as assets held for sale and liabilities held for sale on Southern Company's balance sheet as of December 31, 2018. On July 22, 2019, PowerSecure completed the sale of its utility infrastructure services business for approximately $71 million , subject to customary working capital adjustments. In contemplation of this sale, a goodwill impairment charge of $32 million was recorded in the second quarter 2019. In September 2019, PowerSecure reached an agreement to sell its lighting business for approximately $8 million , subject to customary working capital adjustments. In contemplation of this sale, an impairment charge of $18 million was recorded in the third quarter 2019 related to goodwill, identifiable intangibles, and other assets. The related assets and liabilities were classified as held for sale on Southern Company's balance sheet as of September 30, 2019. The sale is expected to close during the fourth quarter 2019. Southern Company is negotiating an agreement to sell one of its leveraged lease investments for approximately $20 million . The net investment in the leveraged lease of approximately $6 million was classified as held for sale on Southern Company's balance sheet as of September 30, 2019. The sale is expected to close during the fourth quarter 2019. The ultimate outcome of these matters cannot be determined at this time. See " Assets Held for Sale " herein for additional information. Alabama Power On September 6, 2019, Alabama Power entered into the Autauga Combined Cycle Acquisition, a purchase and sale agreement to acquire all of the equity interests in Tenaska Alabama II Partners, L.P. Tenaska Alabama II Partners, L.P. owns and operates an approximately 885 -MW combined cycle generation facility in Autauga County, Alabama. The transaction is expected to close by September 1, 2020. As part of the Autauga Combined Cycle Acquisition, Alabama Power will assume an existing power sales agreement under which the full output of the generating facility remains committed to another third party for its remaining term of approximately three years . The estimated revenues from the power sales agreement are expected to offset the associated costs of operation during the remaining term. The completion of the Autauga Combined Cycle Acquisition is subject to the satisfaction or waiver of certain conditions, including, among other customary conditions, approval by the Alabama PSC, as well as (i) the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and (ii) approval by the FERC. All regulatory approvals are expected to be obtained by the end of the third quarter 2020. The ultimate outcome of this matter cannot be determined at this time. Southern Power Acquisitions During the third quarter 2019 , Southern Power acquired a controlling interest in the fuel cell generation facility listed below. Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller Approximate Nameplate Capacity (MW) Location Southern Power Percentage Ownership COD PPA Remaining Period DSGP (a) Fuel Cell Bloom Energy 28 Delaware 100% of Class B N/A (b) 15 years (a) During the second and third quarters 2019, Southern Power made a total investment of approximately $166 million in DSGP and now holds a controlling interest and consolidates 100% of DSGP's operating results. Southern Power records net income attributable to noncontrolling interests for approximately 10 MWs of the facility. (b) Approximately 18 MWs of the 28 -MW facility was repowered between June and August 2019. Construction Projects During the nine months ended September 30, 2019 , Southern Power completed construction of and placed in service the 385 -MW Plant Mankato expansion and continued construction of the Wildhorse Mountain and Reading facilities. Total aggregate construction costs, excluding acquisition costs, are expected to be between $405 million and $450 million for the two facilities under construction. At September 30, 2019 , total costs of construction incurred for these projects were $337 million and are included in CWIP . The ultimate outcome of these matters cannot be determined at this time. Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Nine Months Ended September 30, 2019 Mankato expansion (a) Natural Gas 385 Mankato, MN May 2019 20 years Projects Under Construction as of September 30, 2019 Wildhorse Mountain (b) Wind 100 Pushmataha County, OK Fourth quarter 2019 20 years Reading (c) Wind 200 Osage and Lyon Counties, KS Second quarter 2020 12 years (a) Southern Power has an agreement with a subsidiary of Xcel to sell all of its equity interests in Plant Mankato, including the expansion. The transaction is subject to FERC approval and is expected to close by January 20, 2020. The expansion unit started providing energy under a PPA with Northern States Power on June 1, 2019. See " Sales of Natural Gas and Biomass Plants " below. (b) In May 2018, Southern Power purchased 100% of the Wildhorse Mountain facility. Southern Power entered into a tax equity partnership in June 2019 with funding of tax equity amounts expected to occur upon commercial operation. (c) In August 2018, Southern Power purchased 100% of the membership interests of the Reading facility from the joint development arrangement with Renewable Energy Systems Americas, Inc. Southern Power may enter into a tax equity partnership, in which case it would then own 100% of the class B membership interests. Development Projects Southern Power continues to evaluate and refine the deployment of wind turbine equipment purchased in 2016 and 2017 to potential joint development and construction projects as well as the amount of MW capacity to be constructed. During 2019, certain wind turbine equipment was sold, resulting in gains totaling approximately $17 million . Sales of Natural Gas and Biomass Plants On June 13, 2019, Southern Power completed the sale of its equity interests in Nacogdoches Power, LLC, the owner of an approximately 115 -MW biomass facility located in Nacogdoches County, Texas, to Austin Energy, for a cash purchase price of approximately $461 million . This sale resulted in an $88 million after-tax gain. In November 2018, Southern Power entered into an agreement with Northern States Power (a subsidiary of Xcel) to sell all of its equity interests in Plant Mankato for an aggregate purchase price of approximately $650 million , subject to certain state commission approvals. On September 27, 2019, the Minnesota Public Utilities Commission denied approval of the transaction. A newly-formed subsidiary of Xcel has agreed to purchase all of the equity interests in Plant Mankato subject to FERC approval and other customary conditions to closing. The transaction is expected to close by January 20, 2020. If the transaction does not close by this date, either party may terminate the transaction, which would result in the payment of a termination fee to Southern Power of up to $25 million . The ultimate outcome of this matter cannot be determined at this time. The assets and liabilities of Plant Mankato are classified as assets held for sale and liabilities held for sale on Southern Company's and Southern Power's balance sheets as of September 30, 2019 and December 31, 2018. See " Assets Held for Sale " herein for additional information. Assets Subject to Lien Under the terms of the PPAs for Plant Mankato, approximately $545 million of assets, primarily related to property, plant, and equipment, are subject to lien at September 30, 2019 . Assets Held for Sale As discussed above, Southern Company and Southern Power each have assets and liabilities held for sale on their balance sheets at September 30, 2019 and December 31, 2018. Assets and liabilities held for sale have been classified separately on each company's balance sheet at the lower of carrying value or fair value less costs to sell at the time the criteria for held-for-sale classification were met. For assets and liabilities held for sale recorded at fair value on a nonrecurring basis, the fair value of assets held for sale is based primarily on unobservable inputs (Level 3), which includes the agreed upon sales prices in executed sales agreements. Upon classification as held for sale in November 2018 and April 2019 for Plant Mankato and Plant Nacogdoches, respectively, Southern Power ceased recognizing depreciation and amortization on the long-lived assets to be sold. The following table provides Southern Company's and Southern Power's major classes of assets and liabilities classified as held for sale at September 30, 2019 and December 31, 2018 : Southern Company Southern Power (in millions) At September 30, 2019 Assets Held for Sale: Current assets $ 17 $ 12 Total property, plant, and equipment 551 546 Goodwill and other intangible assets 40 40 Other non-current assets 40 14 Total Assets Held for Sale $ 648 $ 612 Liabilities Held for Sale: Current liabilities $ 6 $ 3 Other non-current liabilities 20 — Total Liabilities Held for Sale $ 26 $ 3 At December 31, 2018 Assets Held for Sale: Current assets $ 393 $ 8 Total property, plant, and equipment 4,583 536 Other intangible assets 40 40 Other non-current assets 727 — Total Assets Held for Sale $ 5,743 $ 584 Liabilities Held for Sale: Current liabilities $ 425 $ 15 Long-term debt 1,286 — Accumulated deferred income taxes 618 — Other non-current liabilities 932 — Total Liabilities Held for Sale $ 3,261 $ 15 Southern Company and Southern Power each concluded that the sale of their assets, both individually and combined, did not represent a strategic shift in operations that has, or is expected to have, a major effect on its operations and financial results; therefore, none of the assets related to the sales have been classified as discontinued operations for any of the periods presented. Gulf Power and Southern Power's equity interests in Plant Oleander and Plant Stanton Unit A (together, the Florida Plants) and Plant Nacogdoches represented individually significant components of Southern Company and Southern Power, respectively; therefore, pre-tax profit for these components for the three and nine months ended September 30, 2019 and 2018 is presented below: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) Earnings before income taxes: Gulf Power $ — $ 59 $ — $ 146 Southern Power's Florida Plants $ — $ 18 $ — $ 40 Southern Power's Plant Nacogdoches (*) $ — $ 7 $ 16 $ 20 (*) Earnings before income taxes for Plant Nacogdoches for the nine months ended September 30, 2019 represents January 1, 2019 through June 13, 2019 (the divestiture date).

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
LEASES	LEASES On January 1, 2019, the registrants adopted the provisions of FASB ASC Topic 842 (as amended), Leases (ASC 842), which require lessees to recognize leases with a term of greater than 12 months on the balance sheet as lease obligations, representing the discounted future fixed payments due, along with right-of-use (ROU) assets that will be amortized over the term of each lease. The registrants elected the transition methodology provided by ASC 842, whereby the applicable requirements are applied on a prospective basis as of the adoption date of January 1, 2019, without restating prior periods. The registrants also elected the package of practical expedients provided by ASC 842 that allows prior determinations of whether existing contracts are, or contain, leases and the classification of existing leases to continue without reassessment. Additionally, the registrants applied the use-of-hindsight practical expedient in determining lease terms as of the date of adoption and elected the practical expedient that allows existing land easements not previously accounted for as leases not to be reassessed. Lessee As lessee, the registrants lease certain electric generating units (including renewable energy facilities), real estate/land, communication towers, railcars, and other equipment and vehicles. The major categories of lease obligations are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Electric generating units $ 988 $ 125 $ 1,488 $ — $ — $ — Real estate/land 785 4 57 2 395 77 Communication towers 150 2 3 — — 13 Railcars 51 23 25 3 — — Other 89 9 14 2 — 1 Total $ 2,063 $ 163 $ 1,587 $ 7 $ 395 $ 91 Real estate/land leases primarily consist of commercial real estate leases at Southern Company, Georgia Power, and Southern Company Gas and various land leases primarily associated with renewable energy facilities at Southern Power. The commercial real estate leases have remaining terms of up to 25 years while the land leases have remaining terms of up to 47 years, including renewal periods. Communication towers are leased for the installation of equipment to provide cellular phone service to customers and to support the automated meter infrastructure programs at the traditional electric operating companies. Communication tower leases have terms of up to 10 years with options to renew for periods up to 20 years. While renewal options exist in many of the leases, other than for land leases associated with renewable energy facilities, the expected term used in calculating the lease obligation generally reflects only the noncancelable period of the lease as it is not considered reasonably certain that the lease will be extended. The expected term of land leases associated with renewable energy facilities includes renewal periods reasonably certain of exercise resulting in an expected lease term at least equal to the expected life of the renewable energy facilities. Contracts that Contain a Lease While not specifically structured as a lease, some of the PPAs at Alabama Power and Georgia Power are deemed to represent a lease of the underlying electric generating units when the terms of the PPA convey the right to control the use of the underlying assets. Amounts recorded for leases of electric generating units are generally based on the amount of scheduled capacity payments due over the remaining term of the affiliate PPA, which varies between three and 18 years. Georgia Power has several PPAs with Southern Power that Georgia Power accounts for as leases with a lease obligation of approximately $625 million at September 30, 2019 . The amount paid for energy under these affiliate PPAs reflects a price that would be paid in an arm's-length transaction as those amounts have been reviewed and approved by the Georgia PSC. During the third quarter 2019 , Alabama Power entered into additional long-term PPAs totaling approximately 640 MWs of additional generating capacity consisting of combined cycle generation expected to commence in 2020 and solar generation coupled with battery energy storage systems expected to commence in 2022 through 2024. Both the combined cycle PPA and the battery storage system portion of the solar generation PPAs are deemed operating leases. The estimated minimum lease payments for these agreements total $95 million . See Note (B) under " Alabama Power " for additional information. Short-term Leases Leases with an initial term of 12 months or less are not recorded on the balance sheet; the registrants generally recognize lease expense for these leases on a straight-line basis over the lease term. Residual Value Guarantees Residual value guarantees exist primarily in railcar leases at Alabama Power and Georgia Power and the amounts probable of being paid under those guarantees are included in the lease payments. All such amounts are immaterial as of September 30, 2019 . Lease and Nonlease Components For all asset categories, with the exception of electric generating units, gas pipelines, and real estate leases, the registrants combine lease payments and any nonlease components, such as asset maintenance, for purposes of calculating the lease obligation and the right-of-use asset. Balance sheet amounts recorded for operating and finance leases are as follows: As of September 30, 2019 Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating Leases Operating lease ROU assets, net $ 1,823 $ 143 $ 1,461 $ 7 $ 368 $ 92 Operating lease obligations - current $ 229 $ 49 $ 143 $ 2 $ 22 $ 14 Operating lease obligations - non current 1,606 109 1,287 5 373 77 Total operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance Leases Finance lease ROU assets, net $ 220 $ 4 $ 134 $ — $ — $ — Finance lease obligations - current $ 21 $ 1 $ 12 $ — $ — $ — Finance lease obligations - noncurrent 207 4 145 — — — Total finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — (*) Includes operating lease ROU assets, net and operating lease obligations classified as held for sale. Lease costs for the three and nine months ended September 30, 2019 , which includes both amounts recognized as operations and maintenance expense and amounts capitalized as part of the cost of another asset, are as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease cost Operating lease cost $ 94 $ 29 $ 53 $ 1 $ 7 $ 5 Finance lease cost: Amortization of ROU assets 7 — 4 — — — Interest on lease obligations 3 — 4 — — — Total finance lease cost 10 — 8 — — — Short-term lease costs 9 4 5 — — — Variable lease cost 33 4 26 — 1 — Total lease cost $ 146 $ 37 $ 92 $ 1 $ 8 $ 5 For the Nine Months Ended September 30, 2019 Lease cost Operating lease cost $ 243 $ 49 $ 154 $ 2 $ 21 $ 14 Finance lease cost: Amortization of ROU assets 21 1 11 — — — Interest on lease obligations 9 — 14 — — — Total finance lease cost 30 1 25 — — — Short-term lease costs 39 15 17 — — — Variable lease cost 81 6 67 — 3 — Sublease income (1 ) (1 ) — — — — Total lease cost $ 392 $ 70 $ 263 $ 2 $ 24 $ 14 Georgia Power has variable lease payments that are based on the amount of energy produced by certain renewable generating facilities subject to PPAs. Other information with respect to cash and noncash activities related to leases, as well as weighted-average lease terms and discount rates, is as follows: For the Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Other information Cash paid for amounts included in the measurements of lease obligations: Operating cash flows from operating leases $ 211 $ 50 $ 130 $ 2 $ 18 $ 13 Operating cash flows from finance leases 3 1 17 — — — Financing cash flows from finance leases 24 — 4 — — — ROU assets obtained in exchange for new operating lease obligations 76 7 18 — — 14 ROU assets obtained in exchange for new finance lease obligations 31 1 24 — — — As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas Weighted-average remaining lease term in years: Operating leases 14.4 3.4 10.4 6.8 33.2 9.6 Finance leases 18.9 12.4 10.8 N/A N/A N/A Weighted-average discount rate: Operating leases 4.56 % 3.33 % 4.46 % 3.98 % 5.68 % 3.73 % Finance leases 5.07 % 3.65 % 10.74 % N/A N/A N/A Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — Payments made under PPAs at Georgia Power for energy generated from certain renewable energy facilities accounted for as operating and finance leases are considered variable lease costs and are therefore not reflected in the above maturity analysis. As of September 30, 2019 , Alabama Power and Southern Power have additional operating leases that have not yet commenced, as detailed in the following table: Southern Company Alabama Power Southern Power Operating lease type PPAs and land PPAs Land Expected commencement date 2019-2024 2020-2024 2019-2022 Longest lease term expiration 28-31 years 28 years 31 years Estimated total obligations (in millions) $159 $95 $64 For additional information on each registrant's operating lease obligations at December 31, 2018, see Note 9 to the financial statements in Item 8 of the Form 10-K. Lessor With the exception of Southern Company Gas, the registrants are each considered lessors in various arrangements that have been determined to contain a lease due to the customer's ability to control the use of the underlying asset owned by the applicable registrant. For the traditional electric operating companies, these arrangements consist of outdoor lighting contracts accounted for as operating leases with initial terms of up to seven years , after which the contracts renew on a month-to-month basis at the customer's option. For Mississippi Power, these arrangements also include tolling arrangements related to electric generating units accounted for as sales-type leases with terms of up to 20 years. For Southern Power, these arrangements consist of PPAs related to electric generating units, including renewable energy facilities, accounted for as operating leases with terms of up to 28 years. For Southern Company, these arrangements also include PPAs related to fuel cells accounted for as operating leases with terms of up to 15 years. Southern Company Gas is the lessor in operating leases related to gas pipelines with remaining terms of up to 24 years. Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26 No profit or loss was recognized by Mississippi Power upon commencement of a sales-type lease during the first quarter 2019. 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. Scheduled payments to be received under outdoor lighting contracts, tolling arrangements, and PPAs accounted for as leases are presented in the following maturity analyses. The undiscounted cash flows to be received under tolling arrangements accounted for as sales-type leases are as follows: As of September 30, 2019 Southern Company Mississippi Power (in millions) 2019 (remaining) $ 4 $ 4 2020 17 17 2021 15 15 2022 15 15 2023 14 14 Thereafter 152 152 Total undiscounted cash flows $ 217 $ 217 Lease receivable 119 119 Difference between undiscounted cash flows and discounted cash flows $ 98 $ 98 The undiscounted cash flows to be received under operating leases and contracts accounted for as operating leases (adjusted for intercompany eliminations) are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Southern Power Southern Company Gas (in millions) 2019 (remaining) $ 39 $ 6 $ 7 $ 8 $ 9 2020 155 26 26 65 35 2021 140 22 18 66 35 2022 121 13 8 68 34 2023 109 5 2 69 34 Thereafter 1,166 22 — 350 497 Total $ 1,730 $ 94 $ 61 $ 626 $ 644 Southern Power receives payments for renewable energy under PPAs accounted for as operating leases that are considered contingent rents and are therefore not reflected in the table above. Southern Power allocates revenue to the nonlease components of PPAs based on the stand-alone selling price of capacity and energy. The undiscounted cash flows to be received under outdoor lighting contracts accounted for as operating leases at Mississippi Power are immaterial.
LEASES	LEASES On January 1, 2019, the registrants adopted the provisions of FASB ASC Topic 842 (as amended), Leases (ASC 842), which require lessees to recognize leases with a term of greater than 12 months on the balance sheet as lease obligations, representing the discounted future fixed payments due, along with right-of-use (ROU) assets that will be amortized over the term of each lease. The registrants elected the transition methodology provided by ASC 842, whereby the applicable requirements are applied on a prospective basis as of the adoption date of January 1, 2019, without restating prior periods. The registrants also elected the package of practical expedients provided by ASC 842 that allows prior determinations of whether existing contracts are, or contain, leases and the classification of existing leases to continue without reassessment. Additionally, the registrants applied the use-of-hindsight practical expedient in determining lease terms as of the date of adoption and elected the practical expedient that allows existing land easements not previously accounted for as leases not to be reassessed. Lessee As lessee, the registrants lease certain electric generating units (including renewable energy facilities), real estate/land, communication towers, railcars, and other equipment and vehicles. The major categories of lease obligations are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Electric generating units $ 988 $ 125 $ 1,488 $ — $ — $ — Real estate/land 785 4 57 2 395 77 Communication towers 150 2 3 — — 13 Railcars 51 23 25 3 — — Other 89 9 14 2 — 1 Total $ 2,063 $ 163 $ 1,587 $ 7 $ 395 $ 91 Real estate/land leases primarily consist of commercial real estate leases at Southern Company, Georgia Power, and Southern Company Gas and various land leases primarily associated with renewable energy facilities at Southern Power. The commercial real estate leases have remaining terms of up to 25 years while the land leases have remaining terms of up to 47 years, including renewal periods. Communication towers are leased for the installation of equipment to provide cellular phone service to customers and to support the automated meter infrastructure programs at the traditional electric operating companies. Communication tower leases have terms of up to 10 years with options to renew for periods up to 20 years. While renewal options exist in many of the leases, other than for land leases associated with renewable energy facilities, the expected term used in calculating the lease obligation generally reflects only the noncancelable period of the lease as it is not considered reasonably certain that the lease will be extended. The expected term of land leases associated with renewable energy facilities includes renewal periods reasonably certain of exercise resulting in an expected lease term at least equal to the expected life of the renewable energy facilities. Contracts that Contain a Lease While not specifically structured as a lease, some of the PPAs at Alabama Power and Georgia Power are deemed to represent a lease of the underlying electric generating units when the terms of the PPA convey the right to control the use of the underlying assets. Amounts recorded for leases of electric generating units are generally based on the amount of scheduled capacity payments due over the remaining term of the affiliate PPA, which varies between three and 18 years. Georgia Power has several PPAs with Southern Power that Georgia Power accounts for as leases with a lease obligation of approximately $625 million at September 30, 2019 . The amount paid for energy under these affiliate PPAs reflects a price that would be paid in an arm's-length transaction as those amounts have been reviewed and approved by the Georgia PSC. During the third quarter 2019 , Alabama Power entered into additional long-term PPAs totaling approximately 640 MWs of additional generating capacity consisting of combined cycle generation expected to commence in 2020 and solar generation coupled with battery energy storage systems expected to commence in 2022 through 2024. Both the combined cycle PPA and the battery storage system portion of the solar generation PPAs are deemed operating leases. The estimated minimum lease payments for these agreements total $95 million . See Note (B) under " Alabama Power " for additional information. Short-term Leases Leases with an initial term of 12 months or less are not recorded on the balance sheet; the registrants generally recognize lease expense for these leases on a straight-line basis over the lease term. Residual Value Guarantees Residual value guarantees exist primarily in railcar leases at Alabama Power and Georgia Power and the amounts probable of being paid under those guarantees are included in the lease payments. All such amounts are immaterial as of September 30, 2019 . Lease and Nonlease Components For all asset categories, with the exception of electric generating units, gas pipelines, and real estate leases, the registrants combine lease payments and any nonlease components, such as asset maintenance, for purposes of calculating the lease obligation and the right-of-use asset. Balance sheet amounts recorded for operating and finance leases are as follows: As of September 30, 2019 Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating Leases Operating lease ROU assets, net $ 1,823 $ 143 $ 1,461 $ 7 $ 368 $ 92 Operating lease obligations - current $ 229 $ 49 $ 143 $ 2 $ 22 $ 14 Operating lease obligations - non current 1,606 109 1,287 5 373 77 Total operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance Leases Finance lease ROU assets, net $ 220 $ 4 $ 134 $ — $ — $ — Finance lease obligations - current $ 21 $ 1 $ 12 $ — $ — $ — Finance lease obligations - noncurrent 207 4 145 — — — Total finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — (*) Includes operating lease ROU assets, net and operating lease obligations classified as held for sale. Lease costs for the three and nine months ended September 30, 2019 , which includes both amounts recognized as operations and maintenance expense and amounts capitalized as part of the cost of another asset, are as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease cost Operating lease cost $ 94 $ 29 $ 53 $ 1 $ 7 $ 5 Finance lease cost: Amortization of ROU assets 7 — 4 — — — Interest on lease obligations 3 — 4 — — — Total finance lease cost 10 — 8 — — — Short-term lease costs 9 4 5 — — — Variable lease cost 33 4 26 — 1 — Total lease cost $ 146 $ 37 $ 92 $ 1 $ 8 $ 5 For the Nine Months Ended September 30, 2019 Lease cost Operating lease cost $ 243 $ 49 $ 154 $ 2 $ 21 $ 14 Finance lease cost: Amortization of ROU assets 21 1 11 — — — Interest on lease obligations 9 — 14 — — — Total finance lease cost 30 1 25 — — — Short-term lease costs 39 15 17 — — — Variable lease cost 81 6 67 — 3 — Sublease income (1 ) (1 ) — — — — Total lease cost $ 392 $ 70 $ 263 $ 2 $ 24 $ 14 Georgia Power has variable lease payments that are based on the amount of energy produced by certain renewable generating facilities subject to PPAs. Other information with respect to cash and noncash activities related to leases, as well as weighted-average lease terms and discount rates, is as follows: For the Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Other information Cash paid for amounts included in the measurements of lease obligations: Operating cash flows from operating leases $ 211 $ 50 $ 130 $ 2 $ 18 $ 13 Operating cash flows from finance leases 3 1 17 — — — Financing cash flows from finance leases 24 — 4 — — — ROU assets obtained in exchange for new operating lease obligations 76 7 18 — — 14 ROU assets obtained in exchange for new finance lease obligations 31 1 24 — — — As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas Weighted-average remaining lease term in years: Operating leases 14.4 3.4 10.4 6.8 33.2 9.6 Finance leases 18.9 12.4 10.8 N/A N/A N/A Weighted-average discount rate: Operating leases 4.56 % 3.33 % 4.46 % 3.98 % 5.68 % 3.73 % Finance leases 5.07 % 3.65 % 10.74 % N/A N/A N/A Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — Payments made under PPAs at Georgia Power for energy generated from certain renewable energy facilities accounted for as operating and finance leases are considered variable lease costs and are therefore not reflected in the above maturity analysis. As of September 30, 2019 , Alabama Power and Southern Power have additional operating leases that have not yet commenced, as detailed in the following table: Southern Company Alabama Power Southern Power Operating lease type PPAs and land PPAs Land Expected commencement date 2019-2024 2020-2024 2019-2022 Longest lease term expiration 28-31 years 28 years 31 years Estimated total obligations (in millions) $159 $95 $64 For additional information on each registrant's operating lease obligations at December 31, 2018, see Note 9 to the financial statements in Item 8 of the Form 10-K. Lessor With the exception of Southern Company Gas, the registrants are each considered lessors in various arrangements that have been determined to contain a lease due to the customer's ability to control the use of the underlying asset owned by the applicable registrant. For the traditional electric operating companies, these arrangements consist of outdoor lighting contracts accounted for as operating leases with initial terms of up to seven years , after which the contracts renew on a month-to-month basis at the customer's option. For Mississippi Power, these arrangements also include tolling arrangements related to electric generating units accounted for as sales-type leases with terms of up to 20 years. For Southern Power, these arrangements consist of PPAs related to electric generating units, including renewable energy facilities, accounted for as operating leases with terms of up to 28 years. For Southern Company, these arrangements also include PPAs related to fuel cells accounted for as operating leases with terms of up to 15 years. Southern Company Gas is the lessor in operating leases related to gas pipelines with remaining terms of up to 24 years. Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26 No profit or loss was recognized by Mississippi Power upon commencement of a sales-type lease during the first quarter 2019. 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. Scheduled payments to be received under outdoor lighting contracts, tolling arrangements, and PPAs accounted for as leases are presented in the following maturity analyses. The undiscounted cash flows to be received under tolling arrangements accounted for as sales-type leases are as follows: As of September 30, 2019 Southern Company Mississippi Power (in millions) 2019 (remaining) $ 4 $ 4 2020 17 17 2021 15 15 2022 15 15 2023 14 14 Thereafter 152 152 Total undiscounted cash flows $ 217 $ 217 Lease receivable 119 119 Difference between undiscounted cash flows and discounted cash flows $ 98 $ 98 The undiscounted cash flows to be received under operating leases and contracts accounted for as operating leases (adjusted for intercompany eliminations) are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Southern Power Southern Company Gas (in millions) 2019 (remaining) $ 39 $ 6 $ 7 $ 8 $ 9 2020 155 26 26 65 35 2021 140 22 18 66 35 2022 121 13 8 68 34 2023 109 5 2 69 34 Thereafter 1,166 22 — 350 497 Total $ 1,730 $ 94 $ 61 $ 626 $ 644 Southern Power receives payments for renewable energy under PPAs accounted for as operating leases that are considered contingent rents and are therefore not reflected in the table above. Southern Power allocates revenue to the nonlease components of PPAs based on the stand-alone selling price of capacity and energy. The undiscounted cash flows to be received under outdoor lighting contracts accounted for as operating leases at Mississippi Power are immaterial.
LEASES	LEASES On January 1, 2019, the registrants adopted the provisions of FASB ASC Topic 842 (as amended), Leases (ASC 842), which require lessees to recognize leases with a term of greater than 12 months on the balance sheet as lease obligations, representing the discounted future fixed payments due, along with right-of-use (ROU) assets that will be amortized over the term of each lease. The registrants elected the transition methodology provided by ASC 842, whereby the applicable requirements are applied on a prospective basis as of the adoption date of January 1, 2019, without restating prior periods. The registrants also elected the package of practical expedients provided by ASC 842 that allows prior determinations of whether existing contracts are, or contain, leases and the classification of existing leases to continue without reassessment. Additionally, the registrants applied the use-of-hindsight practical expedient in determining lease terms as of the date of adoption and elected the practical expedient that allows existing land easements not previously accounted for as leases not to be reassessed. Lessee As lessee, the registrants lease certain electric generating units (including renewable energy facilities), real estate/land, communication towers, railcars, and other equipment and vehicles. The major categories of lease obligations are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Electric generating units $ 988 $ 125 $ 1,488 $ — $ — $ — Real estate/land 785 4 57 2 395 77 Communication towers 150 2 3 — — 13 Railcars 51 23 25 3 — — Other 89 9 14 2 — 1 Total $ 2,063 $ 163 $ 1,587 $ 7 $ 395 $ 91 Real estate/land leases primarily consist of commercial real estate leases at Southern Company, Georgia Power, and Southern Company Gas and various land leases primarily associated with renewable energy facilities at Southern Power. The commercial real estate leases have remaining terms of up to 25 years while the land leases have remaining terms of up to 47 years, including renewal periods. Communication towers are leased for the installation of equipment to provide cellular phone service to customers and to support the automated meter infrastructure programs at the traditional electric operating companies. Communication tower leases have terms of up to 10 years with options to renew for periods up to 20 years. While renewal options exist in many of the leases, other than for land leases associated with renewable energy facilities, the expected term used in calculating the lease obligation generally reflects only the noncancelable period of the lease as it is not considered reasonably certain that the lease will be extended. The expected term of land leases associated with renewable energy facilities includes renewal periods reasonably certain of exercise resulting in an expected lease term at least equal to the expected life of the renewable energy facilities. Contracts that Contain a Lease While not specifically structured as a lease, some of the PPAs at Alabama Power and Georgia Power are deemed to represent a lease of the underlying electric generating units when the terms of the PPA convey the right to control the use of the underlying assets. Amounts recorded for leases of electric generating units are generally based on the amount of scheduled capacity payments due over the remaining term of the affiliate PPA, which varies between three and 18 years. Georgia Power has several PPAs with Southern Power that Georgia Power accounts for as leases with a lease obligation of approximately $625 million at September 30, 2019 . The amount paid for energy under these affiliate PPAs reflects a price that would be paid in an arm's-length transaction as those amounts have been reviewed and approved by the Georgia PSC. During the third quarter 2019 , Alabama Power entered into additional long-term PPAs totaling approximately 640 MWs of additional generating capacity consisting of combined cycle generation expected to commence in 2020 and solar generation coupled with battery energy storage systems expected to commence in 2022 through 2024. Both the combined cycle PPA and the battery storage system portion of the solar generation PPAs are deemed operating leases. The estimated minimum lease payments for these agreements total $95 million . See Note (B) under " Alabama Power " for additional information. Short-term Leases Leases with an initial term of 12 months or less are not recorded on the balance sheet; the registrants generally recognize lease expense for these leases on a straight-line basis over the lease term. Residual Value Guarantees Residual value guarantees exist primarily in railcar leases at Alabama Power and Georgia Power and the amounts probable of being paid under those guarantees are included in the lease payments. All such amounts are immaterial as of September 30, 2019 . Lease and Nonlease Components For all asset categories, with the exception of electric generating units, gas pipelines, and real estate leases, the registrants combine lease payments and any nonlease components, such as asset maintenance, for purposes of calculating the lease obligation and the right-of-use asset. Balance sheet amounts recorded for operating and finance leases are as follows: As of September 30, 2019 Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating Leases Operating lease ROU assets, net $ 1,823 $ 143 $ 1,461 $ 7 $ 368 $ 92 Operating lease obligations - current $ 229 $ 49 $ 143 $ 2 $ 22 $ 14 Operating lease obligations - non current 1,606 109 1,287 5 373 77 Total operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance Leases Finance lease ROU assets, net $ 220 $ 4 $ 134 $ — $ — $ — Finance lease obligations - current $ 21 $ 1 $ 12 $ — $ — $ — Finance lease obligations - noncurrent 207 4 145 — — — Total finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — (*) Includes operating lease ROU assets, net and operating lease obligations classified as held for sale. Lease costs for the three and nine months ended September 30, 2019 , which includes both amounts recognized as operations and maintenance expense and amounts capitalized as part of the cost of another asset, are as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease cost Operating lease cost $ 94 $ 29 $ 53 $ 1 $ 7 $ 5 Finance lease cost: Amortization of ROU assets 7 — 4 — — — Interest on lease obligations 3 — 4 — — — Total finance lease cost 10 — 8 — — — Short-term lease costs 9 4 5 — — — Variable lease cost 33 4 26 — 1 — Total lease cost $ 146 $ 37 $ 92 $ 1 $ 8 $ 5 For the Nine Months Ended September 30, 2019 Lease cost Operating lease cost $ 243 $ 49 $ 154 $ 2 $ 21 $ 14 Finance lease cost: Amortization of ROU assets 21 1 11 — — — Interest on lease obligations 9 — 14 — — — Total finance lease cost 30 1 25 — — — Short-term lease costs 39 15 17 — — — Variable lease cost 81 6 67 — 3 — Sublease income (1 ) (1 ) — — — — Total lease cost $ 392 $ 70 $ 263 $ 2 $ 24 $ 14 Georgia Power has variable lease payments that are based on the amount of energy produced by certain renewable generating facilities subject to PPAs. Other information with respect to cash and noncash activities related to leases, as well as weighted-average lease terms and discount rates, is as follows: For the Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Other information Cash paid for amounts included in the measurements of lease obligations: Operating cash flows from operating leases $ 211 $ 50 $ 130 $ 2 $ 18 $ 13 Operating cash flows from finance leases 3 1 17 — — — Financing cash flows from finance leases 24 — 4 — — — ROU assets obtained in exchange for new operating lease obligations 76 7 18 — — 14 ROU assets obtained in exchange for new finance lease obligations 31 1 24 — — — As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas Weighted-average remaining lease term in years: Operating leases 14.4 3.4 10.4 6.8 33.2 9.6 Finance leases 18.9 12.4 10.8 N/A N/A N/A Weighted-average discount rate: Operating leases 4.56 % 3.33 % 4.46 % 3.98 % 5.68 % 3.73 % Finance leases 5.07 % 3.65 % 10.74 % N/A N/A N/A Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — Payments made under PPAs at Georgia Power for energy generated from certain renewable energy facilities accounted for as operating and finance leases are considered variable lease costs and are therefore not reflected in the above maturity analysis. As of September 30, 2019 , Alabama Power and Southern Power have additional operating leases that have not yet commenced, as detailed in the following table: Southern Company Alabama Power Southern Power Operating lease type PPAs and land PPAs Land Expected commencement date 2019-2024 2020-2024 2019-2022 Longest lease term expiration 28-31 years 28 years 31 years Estimated total obligations (in millions) $159 $95 $64 For additional information on each registrant's operating lease obligations at December 31, 2018, see Note 9 to the financial statements in Item 8 of the Form 10-K. Lessor With the exception of Southern Company Gas, the registrants are each considered lessors in various arrangements that have been determined to contain a lease due to the customer's ability to control the use of the underlying asset owned by the applicable registrant. For the traditional electric operating companies, these arrangements consist of outdoor lighting contracts accounted for as operating leases with initial terms of up to seven years , after which the contracts renew on a month-to-month basis at the customer's option. For Mississippi Power, these arrangements also include tolling arrangements related to electric generating units accounted for as sales-type leases with terms of up to 20 years. For Southern Power, these arrangements consist of PPAs related to electric generating units, including renewable energy facilities, accounted for as operating leases with terms of up to 28 years. For Southern Company, these arrangements also include PPAs related to fuel cells accounted for as operating leases with terms of up to 15 years. Southern Company Gas is the lessor in operating leases related to gas pipelines with remaining terms of up to 24 years. Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26 No profit or loss was recognized by Mississippi Power upon commencement of a sales-type lease during the first quarter 2019. 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. Scheduled payments to be received under outdoor lighting contracts, tolling arrangements, and PPAs accounted for as leases are presented in the following maturity analyses. The undiscounted cash flows to be received under tolling arrangements accounted for as sales-type leases are as follows: As of September 30, 2019 Southern Company Mississippi Power (in millions) 2019 (remaining) $ 4 $ 4 2020 17 17 2021 15 15 2022 15 15 2023 14 14 Thereafter 152 152 Total undiscounted cash flows $ 217 $ 217 Lease receivable 119 119 Difference between undiscounted cash flows and discounted cash flows $ 98 $ 98 The undiscounted cash flows to be received under operating leases and contracts accounted for as operating leases (adjusted for intercompany eliminations) are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Southern Power Southern Company Gas (in millions) 2019 (remaining) $ 39 $ 6 $ 7 $ 8 $ 9 2020 155 26 26 65 35 2021 140 22 18 66 35 2022 121 13 8 68 34 2023 109 5 2 69 34 Thereafter 1,166 22 — 350 497 Total $ 1,730 $ 94 $ 61 $ 626 $ 644 Southern Power receives payments for renewable energy under PPAs accounted for as operating leases that are considered contingent rents and are therefore not reflected in the table above. Southern Power allocates revenue to the nonlease components of PPAs based on the stand-alone selling price of capacity and energy. The undiscounted cash flows to be received under outdoor lighting contracts accounted for as operating leases at Mississippi Power are immaterial.
LEASES	LEASES On January 1, 2019, the registrants adopted the provisions of FASB ASC Topic 842 (as amended), Leases (ASC 842), which require lessees to recognize leases with a term of greater than 12 months on the balance sheet as lease obligations, representing the discounted future fixed payments due, along with right-of-use (ROU) assets that will be amortized over the term of each lease. The registrants elected the transition methodology provided by ASC 842, whereby the applicable requirements are applied on a prospective basis as of the adoption date of January 1, 2019, without restating prior periods. The registrants also elected the package of practical expedients provided by ASC 842 that allows prior determinations of whether existing contracts are, or contain, leases and the classification of existing leases to continue without reassessment. Additionally, the registrants applied the use-of-hindsight practical expedient in determining lease terms as of the date of adoption and elected the practical expedient that allows existing land easements not previously accounted for as leases not to be reassessed. Lessee As lessee, the registrants lease certain electric generating units (including renewable energy facilities), real estate/land, communication towers, railcars, and other equipment and vehicles. The major categories of lease obligations are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Electric generating units $ 988 $ 125 $ 1,488 $ — $ — $ — Real estate/land 785 4 57 2 395 77 Communication towers 150 2 3 — — 13 Railcars 51 23 25 3 — — Other 89 9 14 2 — 1 Total $ 2,063 $ 163 $ 1,587 $ 7 $ 395 $ 91 Real estate/land leases primarily consist of commercial real estate leases at Southern Company, Georgia Power, and Southern Company Gas and various land leases primarily associated with renewable energy facilities at Southern Power. The commercial real estate leases have remaining terms of up to 25 years while the land leases have remaining terms of up to 47 years, including renewal periods. Communication towers are leased for the installation of equipment to provide cellular phone service to customers and to support the automated meter infrastructure programs at the traditional electric operating companies. Communication tower leases have terms of up to 10 years with options to renew for periods up to 20 years. While renewal options exist in many of the leases, other than for land leases associated with renewable energy facilities, the expected term used in calculating the lease obligation generally reflects only the noncancelable period of the lease as it is not considered reasonably certain that the lease will be extended. The expected term of land leases associated with renewable energy facilities includes renewal periods reasonably certain of exercise resulting in an expected lease term at least equal to the expected life of the renewable energy facilities. Contracts that Contain a Lease While not specifically structured as a lease, some of the PPAs at Alabama Power and Georgia Power are deemed to represent a lease of the underlying electric generating units when the terms of the PPA convey the right to control the use of the underlying assets. Amounts recorded for leases of electric generating units are generally based on the amount of scheduled capacity payments due over the remaining term of the affiliate PPA, which varies between three and 18 years. Georgia Power has several PPAs with Southern Power that Georgia Power accounts for as leases with a lease obligation of approximately $625 million at September 30, 2019 . The amount paid for energy under these affiliate PPAs reflects a price that would be paid in an arm's-length transaction as those amounts have been reviewed and approved by the Georgia PSC. During the third quarter 2019 , Alabama Power entered into additional long-term PPAs totaling approximately 640 MWs of additional generating capacity consisting of combined cycle generation expected to commence in 2020 and solar generation coupled with battery energy storage systems expected to commence in 2022 through 2024. Both the combined cycle PPA and the battery storage system portion of the solar generation PPAs are deemed operating leases. The estimated minimum lease payments for these agreements total $95 million . See Note (B) under " Alabama Power " for additional information. Short-term Leases Leases with an initial term of 12 months or less are not recorded on the balance sheet; the registrants generally recognize lease expense for these leases on a straight-line basis over the lease term. Residual Value Guarantees Residual value guarantees exist primarily in railcar leases at Alabama Power and Georgia Power and the amounts probable of being paid under those guarantees are included in the lease payments. All such amounts are immaterial as of September 30, 2019 . Lease and Nonlease Components For all asset categories, with the exception of electric generating units, gas pipelines, and real estate leases, the registrants combine lease payments and any nonlease components, such as asset maintenance, for purposes of calculating the lease obligation and the right-of-use asset. Balance sheet amounts recorded for operating and finance leases are as follows: As of September 30, 2019 Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating Leases Operating lease ROU assets, net $ 1,823 $ 143 $ 1,461 $ 7 $ 368 $ 92 Operating lease obligations - current $ 229 $ 49 $ 143 $ 2 $ 22 $ 14 Operating lease obligations - non current 1,606 109 1,287 5 373 77 Total operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance Leases Finance lease ROU assets, net $ 220 $ 4 $ 134 $ — $ — $ — Finance lease obligations - current $ 21 $ 1 $ 12 $ — $ — $ — Finance lease obligations - noncurrent 207 4 145 — — — Total finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — (*) Includes operating lease ROU assets, net and operating lease obligations classified as held for sale. Lease costs for the three and nine months ended September 30, 2019 , which includes both amounts recognized as operations and maintenance expense and amounts capitalized as part of the cost of another asset, are as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease cost Operating lease cost $ 94 $ 29 $ 53 $ 1 $ 7 $ 5 Finance lease cost: Amortization of ROU assets 7 — 4 — — — Interest on lease obligations 3 — 4 — — — Total finance lease cost 10 — 8 — — — Short-term lease costs 9 4 5 — — — Variable lease cost 33 4 26 — 1 — Total lease cost $ 146 $ 37 $ 92 $ 1 $ 8 $ 5 For the Nine Months Ended September 30, 2019 Lease cost Operating lease cost $ 243 $ 49 $ 154 $ 2 $ 21 $ 14 Finance lease cost: Amortization of ROU assets 21 1 11 — — — Interest on lease obligations 9 — 14 — — — Total finance lease cost 30 1 25 — — — Short-term lease costs 39 15 17 — — — Variable lease cost 81 6 67 — 3 — Sublease income (1 ) (1 ) — — — — Total lease cost $ 392 $ 70 $ 263 $ 2 $ 24 $ 14 Georgia Power has variable lease payments that are based on the amount of energy produced by certain renewable generating facilities subject to PPAs. Other information with respect to cash and noncash activities related to leases, as well as weighted-average lease terms and discount rates, is as follows: For the Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Other information Cash paid for amounts included in the measurements of lease obligations: Operating cash flows from operating leases $ 211 $ 50 $ 130 $ 2 $ 18 $ 13 Operating cash flows from finance leases 3 1 17 — — — Financing cash flows from finance leases 24 — 4 — — — ROU assets obtained in exchange for new operating lease obligations 76 7 18 — — 14 ROU assets obtained in exchange for new finance lease obligations 31 1 24 — — — As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas Weighted-average remaining lease term in years: Operating leases 14.4 3.4 10.4 6.8 33.2 9.6 Finance leases 18.9 12.4 10.8 N/A N/A N/A Weighted-average discount rate: Operating leases 4.56 % 3.33 % 4.46 % 3.98 % 5.68 % 3.73 % Finance leases 5.07 % 3.65 % 10.74 % N/A N/A N/A Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — Payments made under PPAs at Georgia Power for energy generated from certain renewable energy facilities accounted for as operating and finance leases are considered variable lease costs and are therefore not reflected in the above maturity analysis. As of September 30, 2019 , Alabama Power and Southern Power have additional operating leases that have not yet commenced, as detailed in the following table: Southern Company Alabama Power Southern Power Operating lease type PPAs and land PPAs Land Expected commencement date 2019-2024 2020-2024 2019-2022 Longest lease term expiration 28-31 years 28 years 31 years Estimated total obligations (in millions) $159 $95 $64 For additional information on each registrant's operating lease obligations at December 31, 2018, see Note 9 to the financial statements in Item 8 of the Form 10-K. Lessor With the exception of Southern Company Gas, the registrants are each considered lessors in various arrangements that have been determined to contain a lease due to the customer's ability to control the use of the underlying asset owned by the applicable registrant. For the traditional electric operating companies, these arrangements consist of outdoor lighting contracts accounted for as operating leases with initial terms of up to seven years , after which the contracts renew on a month-to-month basis at the customer's option. For Mississippi Power, these arrangements also include tolling arrangements related to electric generating units accounted for as sales-type leases with terms of up to 20 years. For Southern Power, these arrangements consist of PPAs related to electric generating units, including renewable energy facilities, accounted for as operating leases with terms of up to 28 years. For Southern Company, these arrangements also include PPAs related to fuel cells accounted for as operating leases with terms of up to 15 years. Southern Company Gas is the lessor in operating leases related to gas pipelines with remaining terms of up to 24 years. Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26 No profit or loss was recognized by Mississippi Power upon commencement of a sales-type lease during the first quarter 2019. 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. Scheduled payments to be received under outdoor lighting contracts, tolling arrangements, and PPAs accounted for as leases are presented in the following maturity analyses. The undiscounted cash flows to be received under tolling arrangements accounted for as sales-type leases are as follows: As of September 30, 2019 Southern Company Mississippi Power (in millions) 2019 (remaining) $ 4 $ 4 2020 17 17 2021 15 15 2022 15 15 2023 14 14 Thereafter 152 152 Total undiscounted cash flows $ 217 $ 217 Lease receivable 119 119 Difference between undiscounted cash flows and discounted cash flows $ 98 $ 98 The undiscounted cash flows to be received under operating leases and contracts accounted for as operating leases (adjusted for intercompany eliminations) are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Southern Power Southern Company Gas (in millions) 2019 (remaining) $ 39 $ 6 $ 7 $ 8 $ 9 2020 155 26 26 65 35 2021 140 22 18 66 35 2022 121 13 8 68 34 2023 109 5 2 69 34 Thereafter 1,166 22 — 350 497 Total $ 1,730 $ 94 $ 61 $ 626 $ 644 Southern Power receives payments for renewable energy under PPAs accounted for as operating leases that are considered contingent rents and are therefore not reflected in the table above. Southern Power allocates revenue to the nonlease components of PPAs based on the stand-alone selling price of capacity and energy. The undiscounted cash flows to be received under outdoor lighting contracts accounted for as operating leases at Mississippi Power are immaterial.

Segment and Related Information

Segment and Related Information	9 Months Ended
	Sep. 30, 2019
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 $116 million and $320 million for the three and nine months ended September 30, 2019 , respectively, and $134 million and $326 million for the three and nine months ended September 30, 2018 , respectively. Revenues from sales of natural gas from Southern Company Gas to the traditional electric operating companies were $9 million and $13 million for the three and nine months ended September 30, 2019 , respectively, and $14 million and $22 million for the three and nine months ended September 30, 2018 , respectively. Revenues from sales of natural gas from Southern Company Gas to Southern Power were $20 million and $53 million for the three and nine months ended September 30, 2019 , respectively, and $38 million and $96 million for the three and nine months ended September 30, 2018 , respectively. 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, such as distributed energy infrastructure and energy efficiency products and services, to customers, 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 and nine months ended September 30, 2019 and 2018 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 September 30, 2019 Operating revenues $ 4,908 $ 574 $ (119 ) $ 5,363 $ 498 $ 146 $ (12 ) $ 5,995 Segment net income (loss) (a)(b)(c)(d) 1,373 86 — 1,459 (29 ) (110 ) (4 ) 1,316 Nine Months Ended September 30, 2019 Operating revenues $ 12,252 $ 1,527 $ (331 ) $ 13,448 $ 2,661 $ 514 $ (118 ) $ 16,505 Segment net income (loss) (a)(b)(c)(d)(e) 2,719 316 — 3,035 347 931 (15 ) 4,298 At September 30, 2019 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 80,493 14,397 (756 ) 94,134 21,047 3,569 (1,159 ) 117,591 Three Months Ended September 30, 2018 Operating revenues $ 5,014 $ 635 $ (140 ) $ 5,509 $ 492 $ 202 $ (44 ) $ 6,159 Segment net income (loss) (a)(b)(e)(f) 1,148 92 — 1,240 46 (119 ) (3 ) 1,164 Nine Months Ended September 30, 2018 Operating revenues $ 13,117 $ 1,699 $ (360 ) $ 14,456 $ 2,861 $ 984 $ (143 ) $ 18,158 Segment net income (loss) (a)(b)(e)(f) 1,711 235 — 1,946 294 (292 ) — 1,948 At December 31, 2018 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 298 $ — $ 5,315 Total assets 79,382 14,883 (306 ) 93,959 21,448 3,285 (1,778 ) 116,914 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes pre-tax charges for estimated losses on plants under construction of $4 million ( $3 million after tax) and $1 million ( $1 million after tax) for the three months ended September 30, 2019 and 2018 , respectively, and $10 million ( $7 million after tax) and $1.1 billion ( $0.8 billion after tax) for the nine months ended September 30, 2019 and 2018 , respectively. See Note 2 to the financial statements in Item 8 of the Form 10-K and Note (B) under "Georgia Power – Nuclear Construction" and " Mississippi Power – Kemper County Energy Facility " 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 nine months ended September 30, 2019 , of which $4 million ( $4 million after tax) was recorded in the three months ended September 30, 2019 , as well as impairment charges in contemplation of the sales of two of PowerSecure's business units totaling $18 million and $50 million for the three and nine months ended September 30, 2019 , respectively. See Note (K) under " Southern Company " for additional information. (d) Segment net income (loss) for Southern Company Gas includes a pre-tax impairment charge of $92 million ( $65 million after tax) related to a natural gas storage facility in Louisiana. See Note (C) under "Other Matters – Southern Company Gas" for additional information. (e) Segment net income (loss) for Southern Power includes a $23 million pre-tax gain ( $88 million gain after tax) on the sale of Plant Nacogdoches for the nine months ended September 30, 2019 and pre-tax impairment charges of $36 million ( $27 million after tax) and $155 million ( $116 million after tax) for the three and nine months ended September 30, 2018 , respectively. See Note (K) under " Southern Power " and Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Power – Development Projects" and " – Sale of Natural Gas Plants" for additional information. (f) Segment net income (loss) for Southern Company Gas includes a net gain on dispositions of $353 million ( $40 million gain after tax) and $317 million ( $35 million loss after tax) for the three and nine months ended September 30, 2018, respectively, related to the Southern Company Gas Dispositions and a goodwill impairment charge of $42 million for the nine months ended September 30, 2018 related to the sale of Pivotal Home Solutions. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. Products and Services Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended September 30, 2019 $ 4,512 $ 625 $ 226 $ 5,363 Three Months Ended September 30, 2018 4,605 698 206 5,509 Nine Months Ended September 30, 2019 $ 11,136 $ 1,667 $ 645 $ 13,448 Nine Months Ended September 30, 2018 11,913 1,937 606 14,456 Southern Company Gas' Revenues Gas (a) Gas (b) Other Total (in millions) Three Months Ended September 30, 2019 $ 445 $ 39 $ 14 $ 498 Three Months Ended September 30, 2018 438 44 10 492 Nine Months Ended September 30, 2019 $ 2,169 $ 326 $ 166 $ 2,661 Nine Months Ended September 30, 2018 2,276 403 182 2,861 (a) Operating revenues for the three gas distribution operations dispositions were $7 million and $245 million for the three and nine months ended September 30, 2018 , respectively. (b) Operating revenues for Pivotal Home Solutions were $55 million for the nine months ended September 30, 2018 , respectively. 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, two significant pipeline construction projects, and a 50% joint ownership interest in the Dalton Pipeline. 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. This includes Southern Company Gas' storage and fuels operations, its investment in Triton through the completion of its sale on May 29, 2019, and other subsidiaries that fall below the quantitative threshold for separate disclosure. See Note (E) under " Southern Company Gas " for additional information and related disclosures. Business segment financial data for the three and nine months ended September 30, 2019 and 2018 was as follows: Gas Distribution Operations (a) Gas Pipeline Investments Wholesale Gas Services (b) Gas Marketing Services (c)(d) Total All Other (e) Eliminations Consolidated (in millions) Three Months Ended September 30, 2019 Operating revenues $ 448 $ 8 $ (2 ) $ 39 $ 493 $ 10 $ (5 ) $ 498 Segment net income (loss) 37 6 (9 ) (4 ) 30 (59 ) — (29 ) Nine Months Ended September 30, 2019 Operating revenues $ 2,188 $ 24 $ 132 $ 326 $ 2,670 $ 34 $ (43 ) $ 2,661 Segment net income (loss) 228 63 61 54 406 (59 ) — 347 Total assets at September 30, 2019 17,798 1,743 657 1,443 21,641 10,429 (11,023 ) 21,047 Three Months Ended September 30, 2018 Operating revenues $ 441 $ 8 $ (8 ) $ 44 $ 485 $ 13 $ (6 ) $ 492 Segment net income (loss) 74 20 (18 ) (8 ) 68 (22 ) — 46 Nine Months Ended September 30, 2018 Operating revenues $ 2,297 $ 24 $ 142 $ 403 $ 2,866 $ 39 $ (44 ) $ 2,861 Segment net income (loss) 290 68 65 (71 ) 352 (58 ) — 294 Total assets at December 31, 2018 17,266 1,763 1,302 1,587 21,918 11,112 (11,582 ) 21,448 (a) Operating revenues for the three gas distribution operations dispositions were $8 million and $245 million for the three and nine months ended September 30, 2018 , respectively. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. (b) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. A reconciliation of operating revenues and intercompany revenues is shown in the following table. Third Party Gross Revenues Intercompany Revenues Total Gross Revenues Less Gross Gas Costs Operating Revenues (in millions) Three Months Ended September 30, 2019 $ 1,138 $ 72 $ 1,210 $ 1,212 $ (2 ) Three Months Ended September 30, 2018 1,573 82 1,655 1,663 (8 ) Nine Months Ended September 30, 2019 $ 4,287 $ 223 $ 4,510 $ 4,378 $ 132 Nine Months Ended September 30, 2018 4,847 352 5,199 5,057 142 (c) Operating revenues for Pivotal Home Solutions were $55 million for the nine months ended September 30, 2018 . See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information on the sale of Pivotal Home Solutions. (d) Segment net income (loss) for gas marketing services includes a loss on disposition of $34 million for the nine months ended September 30, 2018 and a goodwill impairment charge of $42 million for the nine months ended September 30, 2018 related to the sale of Pivotal Home Solutions. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. (e) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $92 million ( $65 million after tax) for the three and nine months ended September 30, 2019 related to a natural gas storage facility in Louisiana. See Note (C) under "Other Matters – Southern Company Gas" for additional information.

Introduction (Policies)

Introduction (Policies)	9 Months Ended
	Sep. 30, 2019
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, 2018 have been derived from the audited financial statements of each registrant. In the opinion of each registrant's management, the information regarding such registrant furnished herein reflects all adjustments, which, except as otherwise disclosed, are of a normal recurring nature, necessary to present fairly the results of operations for the periods ended September 30, 2019 and 2018 . 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 results of operations, financial position, or cash flows of any registrant.
Recently Adopted Accounting Standards	In 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842)
Goodwill and Other Intangible Assets	Goodwill is not amortized but is subject to an annual impairment test during the fourth quarter of each year or more frequently if impairment indicators arise.
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 recorded an adjustment of $10 million for the nine months ended September 30, 2019 and no material adjustments for the remaining periods reported.
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	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. 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. Foreign Currency Derivatives Southern Company and certain subsidiaries, including Southern Power, may enter into foreign currency derivatives to hedge exposure to changes in foreign currency exchange rates, such as that arising from the issuance of debt denominated in a currency other than U.S. dollars. Derivatives related to forecasted transactions are accounted for as cash flow hedges where the derivatives' fair value gains or losses are recorded in OCI and are reclassified into earnings at the same time and on the same income statement line as the earnings effect of the hedged transactions, including foreign currency gains or losses arising from changes in the U.S. currency exchange rates. The derivatives employed as hedging instruments are structured to minimize ineffectiveness.

Introduction (Tables)

Introduction (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Goodwill	Goodwill at September 30, 2019 and December 31, 2018 was as follows: At September 30, 2019 At December 31, 2018 (in millions) Southern Company $ 5,280 $ 5,315 Southern Company Gas: Gas distribution operations $ 4,034 $ 4,034 Gas marketing services 981 981 Southern Company Gas total $ 5,015 $ 5,015
Schedule of Other Intangible Assets, Indefinite-Lived	Other intangible assets were as follows: At September 30, 2019 At December 31, 2018 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 (a) $ 211 $ (110 ) $ 101 $ 223 $ (94 ) $ 129 Trade names (a) 64 (23 ) 41 70 (21 ) 49 Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 PPA fair value adjustments (b) 389 (64 ) 325 405 (61 ) 344 Other 12 (8 ) 4 11 (5 ) 6 Total other intangible assets subject to amortization $ 740 $ (265 ) $ 475 $ 773 $ (235 ) $ 538 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (265 ) $ 550 $ 848 $ (235 ) $ 613 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments (b) $ 389 $ (64 ) $ 325 $ 405 $ (61 ) $ 344 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (99 ) $ 57 $ 156 $ (84 ) $ 72 Trade names 26 (9 ) 17 26 (7 ) 19 Wholesale gas services Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 Total other intangible assets subject to amortization $ 246 $ (168 ) $ 78 $ 246 $ (145 ) $ 101 (a) The decrease in the gross carrying amount during the nine months ended September 30, 2019 primarily reflects the reclassification to held for sale. See Note (K) for additional information. (b) The decrease in the gross carrying amount during the nine months ended September 30, 2019 reflects the sale of Plant Nacogdoches, partially offset by additional PPA fair value adjustments related to the acquisition of DSGP. See Note (K) under "Southern Power" for additional information.
Schedule of Other Intangible Assets, Finite-Lived	Other intangible assets were as follows: At September 30, 2019 At December 31, 2018 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 (a) $ 211 $ (110 ) $ 101 $ 223 $ (94 ) $ 129 Trade names (a) 64 (23 ) 41 70 (21 ) 49 Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 PPA fair value adjustments (b) 389 (64 ) 325 405 (61 ) 344 Other 12 (8 ) 4 11 (5 ) 6 Total other intangible assets subject to amortization $ 740 $ (265 ) $ 475 $ 773 $ (235 ) $ 538 Other intangible assets not subject to amortization: Federal Communications Commission licenses 75 — 75 75 — 75 Total other intangible assets $ 815 $ (265 ) $ 550 $ 848 $ (235 ) $ 613 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments (b) $ 389 $ (64 ) $ 325 $ 405 $ (61 ) $ 344 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 156 $ (99 ) $ 57 $ 156 $ (84 ) $ 72 Trade names 26 (9 ) 17 26 (7 ) 19 Wholesale gas services Storage and transportation contracts 64 (60 ) 4 64 (54 ) 10 Total other intangible assets subject to amortization $ 246 $ (168 ) $ 78 $ 246 $ (145 ) $ 101 (a) The decrease in the gross carrying amount during the nine months ended September 30, 2019 primarily reflects the reclassification to held for sale. See Note (K) for additional information. (b) The decrease in the gross carrying amount during the nine months ended September 30, 2019 reflects the sale of Plant Nacogdoches, partially offset by additional PPA fair value adjustments related to the acquisition of DSGP. See Note (K) under "Southern Power" for additional information.
Finite-lived Intangible Assets Amortization Expense	Amortization associated with other intangible assets was as follows: Three Months Ended Nine Months Ended September 30, 2019 (in millions) Southern Company (a) $ 14 $ 45 Southern Power (b) $ 4 $ 14 Southern Company Gas Gas marketing services $ 5 $ 17 Wholesale gas services (b) 2 6 Southern Company Gas total $ 7 $ 23 (a) Includes $6 million and $20 million for the three and nine months ended September 30, 2019 , respectively, recorded as a reduction to operating revenues. (b) Recorded as a reduction to operating revenues.
Restrictions on Cash and Cash Equivalents	The following tables provide a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the registrants that had restricted cash at September 30, 2019 and/or December 31, 2018 : Southern Company Southern Company Gas (in millions) At September 30, 2019 Cash and cash equivalents $ 2,931 $ 59 Restricted cash: Other accounts and notes receivable 3 3 Total cash, cash equivalents, and restricted cash $ 2,935 (*) $ 62 (*) Total does not add due to rounding. Southern Company Georgia Power Southern Company Gas (in millions) At December 31, 2018 Cash and cash equivalents $ 1,396 $ 4 $ 64 Cash and cash equivalents held for sale 9 — — Restricted cash: Restricted cash — 108 — Other accounts and notes receivable 114 — 6 Total cash, cash equivalents, and restricted cash $ 1,519 $ 112 $ 70
Schedule of Cash and Cash Equivalents	The following tables provide a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed balance sheets that total to the amounts shown in the condensed statements of cash flows for the registrants that had restricted cash at September 30, 2019 and/or December 31, 2018 : Southern Company Southern Company Gas (in millions) At September 30, 2019 Cash and cash equivalents $ 2,931 $ 59 Restricted cash: Other accounts and notes receivable 3 3 Total cash, cash equivalents, and restricted cash $ 2,935 (*) $ 62 (*) Total does not add due to rounding. Southern Company Georgia Power Southern Company Gas (in millions) At December 31, 2018 Cash and cash equivalents $ 1,396 $ 4 $ 64 Cash and cash equivalents held for sale 9 — — Restricted cash: Restricted cash — 108 — Other accounts and notes receivable 114 — 6 Total cash, cash equivalents, and restricted cash $ 1,519 $ 112 $ 70
Details of AROs included in the balance sheets	Details of the AROs included in the condensed balance sheets of Southern Company, Alabama Power, and Mississippi Power at September 30, 2019 are shown in the following table. There were no material changes in the AROs of Georgia Power or Southern Power during the first nine months of 2019. Southern Company Alabama Power Mississippi Power (in millions) Balance at December 31, 2018 $ 9,394 $ 3,210 $ 160 Liabilities incurred 35 — 1 Liabilities settled (223 ) (76 ) (28 ) Accretion 299 107 5 Cash flow revisions 455 312 57 Balance at September 30, 2019 $ 9,960 $ 3,553 $ 195

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Cost Recovery Clauses	The recovery balances for certain of Alabama Power's, Georgia Power's, and Mississippi Power's regulatory clauses at September 30, 2019 and December 31, 2018 were as follows: Regulatory Clause Balance Sheet Line Item September 30, December 31, (in millions) Alabama Power Rate CNP Compliance Deferred under recovered regulatory clause revenues $ — $ 42 Other regulatory liabilities, deferred 55 — Rate CNP PPA Deferred under recovered regulatory clause revenues 45 25 Retail Energy Cost Recovery (*) Deferred under recovered regulatory clause revenues — 109 Other regulatory liabilities, deferred 21 — Natural Disaster Reserve Other regulatory liabilities, deferred 23 20 Georgia Power Fuel Cost Recovery Receivables – under recovered fuel clause revenues $ — $ 115 Other deferred credits and liabilities 1 — Mississippi Power Fuel Cost Recovery Over recovered regulatory clause liabilities $ 18 $ 8 (*) In accordance with an accounting order issued on February 5, 2019 by the Alabama PSC, Alabama Power utilized $75 million of the 2018 Rate RSE refund liability to reduce the Rate ECR under recovered balance. See Note 2 to the financial statements under "Alabama Power – Rate ECR" in Item 8 of the Form 10-K for additional information.
Requested Recovery of Proposed Increases	Georgia Power has requested recovery of the proposed increases through its existing base rate tariffs as follows: Tariff 2020 2021 2022 (in millions) Traditional base: Levelized $ 210 $ — $ — CCR AROs 158 139 227 Environmental Compliance Cost Recovery 163 — — Demand-Side Management 12 1 1 Municipal Franchise Fee 17 3 5 Total (*) $ 560 $ 144 $ 233 (*) Totals may not add due to rounding.
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) $ 8.0 Construction contingency estimate 0.4 Total project capital cost forecast (a)(b) 8.4 Net investment as of September 30, 2019 (b) (5.5 ) Remaining estimate to complete (a) $ 2.9 (a) Excludes financing costs expected to be capitalized through AFUDC of approximately $300 million . (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 (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables disaggregate revenue sources for the three and nine months ended September 30, 2019 and 2018 : For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Company Operating revenues Retail electric revenues (a) Residential $ 2,056 $ 2,148 $ 4,832 $ 5,266 Commercial 1,508 1,527 3,859 4,084 Industrial 916 901 2,356 2,471 Other 32 29 89 92 Natural gas distribution revenues (b) 445 433 2,169 2,299 Alternative revenue programs (c) — 5 — (23 ) Total retail electric and gas distribution revenues $ 4,957 $ 5,043 $ 13,305 $ 14,189 Wholesale energy revenues (d)(e) 477 521 1,254 1,458 Wholesale capacity revenues (e) 148 177 413 479 Other natural gas revenues (f)(g) 53 54 492 530 Other revenues (h) 360 364 1,041 1,502 Total operating revenues $ 5,995 $ 6,159 $ 16,505 $ 18,158 (a) Retail electric revenues include $8 million , $17 million , $24 million , and $54 million of revenues accounted for as leases for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and a net increase/(reduction) of $(155) million , $(98) million , $(272) million , and $4 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, from certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Natural gas distribution revenues include $3 million for each of the three months ended September 30, 2019 and 2018 and $11 million for each of the nine months ended September 30, 2019 and 2018 of revenues not accounted for under ASC 606. (c) Alternative revenue program revenues are presented net of any previously recognized program amounts billed to customers during the same accounting period. (d) Wholesale energy revenues include $28 million , $63 million , $109 million , and $217 million of revenues accounted for as derivatives for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, primarily related to physical energy sales in the wholesale electricity market. (e) Wholesale energy revenues include $141 million , $130 million , $324 million , and $318 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and wholesale capacity revenues include $15 million , $31 million , $62 million , and $92 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, related to PPAs accounted for as leases. (f) Other natural gas revenues related to Southern Company Gas' energy and risk management activities are presented net of the related costs of those activities and include gross third-party revenues of $1.1 billion , $1.6 billion , $4.3 billion , and $4.8 billion for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of which $0.7 billion , $0.9 billion , $2.7 billion , and $2.7 billion , respectively, relates to contracts that are accounted for as derivatives. See Note (M) under " Southern Company Gas " for additional information on the components of wholesale gas services operating revenues. (g) Other natural gas revenues include $10 million and $37 million for the three and nine months ended September 30, 2019 , respectively, of revenues not accounted for under ASC 606, including $8 million and $24 million , respectively, of revenues accounted for as leases. (h) Other revenues include $93 million , $92 million , $278 million , and $274 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of revenues not accounted for under ASC 606, including $33 million , $35 million , $104 million , and $106 million , respectively, accounted for as leases. Alabama Power Georgia Power Mississippi Power (in millions) For the Three Months Ended September 30, 2019 Operating revenues Retail revenues (a)(b) Residential $ 796 $ 1,174 $ 86 Commercial 493 932 83 Industrial 398 439 79 Other 7 22 3 Total retail electric revenues $ 1,694 $ 2,567 $ 251 Wholesale energy revenues (c) 48 25 114 Wholesale capacity revenues 25 14 1 Other revenues (b)(d) 74 149 4 Total operating revenues $ 1,841 $ 2,755 $ 370 For the Three Months Ended September 30, 2018 Operating revenues Retail revenues (a)(b) Residential $ 721 $ 1,142 $ 85 Commercial 464 877 82 Industrial 392 385 86 Other 7 21 1 Total retail electric revenues $ 1,584 $ 2,425 $ 254 Wholesale energy revenues (c) 62 33 97 Wholesale capacity revenues 26 14 1 Other revenues (b)(d) 68 121 6 Total operating revenues $ 1,740 $ 2,593 $ 358 (a) Retail revenues at Alabama Power, Georgia Power, and Mississippi Power include a net reduction of $(64) million , $(83) million , and $(8) million , respectively, for the three months ended September 30, 2019 and $(12) million , $(47) million , and $(3) million , respectively, for the three months ended September 30, 2018 related to certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Retail revenues and other revenues at Georgia Power include $8 million and $10 million , respectively, for the three months ended September 30, 2019 and $17 million and $34 million , respectively, for the three months ended September 30, 2018 of revenues accounted for as leases. (c) Wholesale energy revenues at Alabama Power, Georgia Power, and Mississippi Power include $3 million , $4 million , and $1 million , respectively, for the three months ended September 30, 2019 and $6 million , $8 million , and $1 million , respectively, for the three months ended September 30, 2018 accounted for as derivatives primarily related to physical energy sales in the wholesale electricity market. (d) Other revenues at Alabama Power and Georgia Power include $36 million and $26 million , respectively, for the three months ended September 30, 2019 and $27 million and $28 million , respectively, for the three months ended September 30, 2018 of revenues not accounted for under ASC 606. Alabama Power Georgia Power Mississippi Power (in millions) For the Nine Months Ended September 30, 2019 Operating revenues Retail revenues (a)(b) Residential $ 1,923 $ 2,693 $ 216 Commercial 1,266 2,372 221 Industrial 1,077 1,055 224 Other 20 61 8 Total retail electric revenues $ 4,286 $ 6,181 $ 669 Wholesale energy revenues (c) 183 66 285 Wholesale capacity revenues 77 41 2 Other revenues (b)(d) 216 418 14 Total operating revenues $ 4,762 $ 6,706 $ 970 For the Nine Months Ended September 30, 2018 Operating revenues Retail revenues (a)(b) Residential $ 1,848 $ 2,671 $ 209 Commercial 1,238 2,343 212 Industrial 1,103 1,036 233 Other 19 62 6 Total retail electric revenues $ 4,208 $ 6,112 $ 660 Wholesale energy revenues (c) 234 99 272 Wholesale capacity revenues 75 41 6 Other revenues (b)(d) 199 349 18 Total operating revenues $ 4,716 $ 6,601 $ 956 (a) Retail revenues at Alabama Power, Georgia Power, and Mississippi Power include a net increase/(reduction) of $(132) million , $(135) million , and $(5) million , respectively, for the nine months ended September 30, 2019 and $113 million , $(35) million , and $(11) million , respectively, for the nine months ended September 30, 2018 related to certain cost recovery mechanisms that are not accounted for as revenue under ASC 606. (b) Retail revenues and other revenues at Georgia Power include $24 million and $33 million , respectively, for the nine months ended September 30, 2019 and $54 million and $100 million , respectively, for the nine months ended September 30, 2018 of revenues accounted for as leases. (c) Wholesale energy revenues at Alabama Power, Georgia Power, and Mississippi Power include $8 million , $12 million , and $2 million , respectively, for the nine months ended September 30, 2019 and $14 million , $21 million , and $3 million , respectively, for the nine months ended September 30, 2018 accounted for as derivatives primarily related to physical energy sales in the wholesale electricity market. (d) Other revenues at Alabama Power and Georgia Power include $95 million and $88 million , respectively, for the nine months ended September 30, 2019 and $79 million and $80 million , respectively, for the nine months ended September 30, 2018 of revenues not accounted for under ASC 606. For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Power PPA capacity revenues (a) $ 131 $ 168 $ 384 $ 450 PPA energy revenues (a) 339 336 857 892 Non-PPA revenues (b) 101 126 276 347 Other revenues 3 5 10 10 Total operating revenues $ 574 $ 635 $ 1,527 $ 1,699 (a) PPA capacity revenues include $31 million , $47 million , $111 million , and $141 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, and PPA energy revenues include $151 million , $139 million , $349 million , and $342 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, related to PPAs accounted for as leases. (b) Non-PPA revenues include $20 million , $47 million , $87 million , and $176 million for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of revenues from short-term sales related to physical energy sales from uncovered capacity in the wholesale electricity market. For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2018 (in millions) Southern Company Gas Operating revenues Natural gas distribution revenues (a) Residential $ 162 $ 149 $ 992 $ 1,082 Commercial 42 45 277 313 Transportation 204 203 673 708 Industrial 3 4 25 28 Other 34 32 202 168 Alternative revenue programs (b) — 5 — (23 ) Total natural gas distribution revenues $ 445 $ 438 $ 2,169 $ 2,276 Gas pipeline investments (c) 8 8 24 24 Wholesale gas services (d) (4 ) (10 ) 110 121 Gas marketing services (e) 39 44 326 403 Other revenues 10 12 32 37 Total operating revenues $ 498 $ 492 $ 2,661 $ 2,861 (a) Natural gas distribution revenues include $3 million for each of the three months ended September 30, 2019 and 2018 and $11 million for each of the nine months ended September 30, 2019 and 2018 of revenues not accounted for under ASC 606. (b) Alternative revenue program revenues are presented net of any previously recognized program amounts billed to customers during the same accounting period. (c) Revenues from gas pipeline investments include $8 million and $24 million for the three and nine months ended September 30, 2019 , respectively, accounted for as leases. (d) Wholesale gas services revenues are presented net of the related costs associated with its energy trading and risk management activities. Operating revenues, as presented, include gross third-party revenues of $1.1 billion , $1.6 billion , $4.3 billion , and $4.8 billion for the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018 , respectively, of which $0.7 billion , $0.9 billion , $2.7 billion , and $2.7 billion , respectively, relates to contracts accounted for as derivatives. See Note (M) under " Southern Company Gas " for additional information on the components of wholesale gas services operating revenues. (e) Gas marketing services include $2 million for the three months ended September 30, 2019 and $13 million and $4 million for the nine months ended September 30, 2019 and 2018 , respectively, of revenues not accounted for under ASC 606.
Contract with Customer, Asset and Liability and Revenue Recognized	The following table reflects revenue from contracts with customers recognized in the three and nine months ended September 30, 2019 included in the contract liability at December 31, 2018 : Three Months Ended Nine Months Ended (in millions) Southern Company $ 4 $ 29 Southern Power — 11 The following table reflects the closing balances of receivables, contract assets, and contract liabilities related to revenues from contracts with customers as of September 30, 2019 and December 31, 2018 : Receivables Contract Assets Contract Liabilities September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 (in millions) Southern Company $ 2,523 $ 2,630 $ 132 $ 102 $ 58 $ 32 Alabama Power 713 520 2 — 12 12 Georgia Power 993 721 91 58 15 7 Mississippi Power 94 100 — — 6 — Southern Power 132 118 — — 3 11 Southern Company Gas 441 952 — — 1 2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	Registrants with revenues from contracts with customers related to these performance obligations remaining at September 30, 2019 expect the revenues to be recognized as follows: 2019 (remaining) 2020 2021 2022 2023 Thereafter (in millions) Southern Company $ 138 $ 419 $ 345 $ 326 $ 317 $ 2,256 Alabama Power 6 23 27 23 22 140 Georgia Power 15 56 47 31 32 83 Southern Power 61 309 291 290 283 2,180

Consolidated Entities and Equ_2

Consolidated Entities and Equity Method Investments (Tables)	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Equity Method Investments	The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2019 and December 31, 2018 and related income from those investments for the three - and nine -month periods ended September 30, 2019 and 2018 were as follows: Investment Balance September 30, 2019 December 31, 2018 (in millions) SNG (a) $ 1,210 $ 1,261 Atlantic Coast Pipeline (b) 109 83 PennEast Pipeline 80 71 Other (c) 88 123 Total $ 1,487 $ 1,538 (a) Decrease primarily relates to the continued amortization of deferred tax assets established upon acquisition. (b) The Atlantic Coast Pipeline has a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Southern Company Gas guarantees 5% of the outstanding borrowings under this facility; this guarantee totaled $85 million as of September 30, 2019. (c) Decrease primarily relates to the sale of Triton. Earnings from Equity Method Investments Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) SNG $ 30 $ 29 $ 104 $ 95 Atlantic Coast Pipeline 3 1 9 4 PennEast Pipeline 2 2 5 4 Other (*) — 2 (3 ) 5 Total $ 35 $ 34 $ 115 $ 108 (*) Decrease primarily relates to the sale of Triton. Selected financial information of SNG for the three and nine months ended September 30, 2019 and 2018 is as follows: Income Statement Information Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) Revenues $ 152 $ 145 $ 473 $ 451 Operating income 82 71 274 230 Net income 60 58 208 190
Schedule of Other Nonoperating Income, by Component	The carrying amounts of Southern Company Gas' equity method investments as of September 30, 2019 and December 31, 2018 and related income from those investments for the three - and nine -month periods ended September 30, 2019 and 2018 were as follows: Investment Balance September 30, 2019 December 31, 2018 (in millions) SNG (a) $ 1,210 $ 1,261 Atlantic Coast Pipeline (b) 109 83 PennEast Pipeline 80 71 Other (c) 88 123 Total $ 1,487 $ 1,538 (a) Decrease primarily relates to the continued amortization of deferred tax assets established upon acquisition. (b) The Atlantic Coast Pipeline has a $3.4 billion revolving credit facility with a stated maturity date of October 2021. Southern Company Gas guarantees 5% of the outstanding borrowings under this facility; this guarantee totaled $85 million as of September 30, 2019. (c) Decrease primarily relates to the sale of Triton. Earnings from Equity Method Investments Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) SNG $ 30 $ 29 $ 104 $ 95 Atlantic Coast Pipeline 3 1 9 4 PennEast Pipeline 2 2 5 4 Other (*) — 2 (3 ) 5 Total $ 35 $ 34 $ 115 $ 108 (*) Decrease primarily relates to the sale of Triton.

Financing (Tables)

Financing (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Credit Arrangements by Company	The following table outlines the committed credit arrangements by company as of September 30, 2019 : Expires Company 2020 2022 2024 Total Unused Due within One Year (in millions) Southern Company (a) $ — $ — $ 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 — 150 150 — Southern Power (b) — — 600 600 591 — Southern Company Gas (c) — — 1,750 1,750 1,745 — Other 30 — — 30 30 30 Southern Company Consolidated $ 33 $ 675 $ 6,900 $ 7,608 $ 7,576 $ 33 (a) Represents the Southern Company parent entity. (b) Does not include Southern Power Company's $120 million continuing letter of credit facility for standby letters of credit expiring in 2021, of which $30 million was unused at September 30, 2019 . Southern Power's subsidiaries are not parties to its bank credit arrangement. (c) 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.
Schedule of Long-term Debt Financing Activities	The following table outlines the long-term debt financing activities for Southern Company and its subsidiaries for the first nine months of 2019 : Company Senior Note Issuances Senior Note Maturities, Redemptions, and Repurchases Revenue Bond Issuances and Reofferings of Purchased Bonds Revenue Bond and Other Long-Term Debt Issuances Other Long-Term Debt Redemptions and Maturities (a) (in millions) Southern Company (b) $ — $ 2,400 $ — $ — $ 1,725 $ — Alabama Power 600 200 — — — 1 Georgia Power 750 — 584 223 835 11 Mississippi Power — — 43 — — — Southern Company Gas — 300 — — 200 50 Other — — — 25 — 14 Elimination (c) — — — — — (7 ) Southern Company Consolidated $ 1,350 $ 2,900 $ 627 $ 248 $ 2,760 $ 69 (a) Includes reductions in finance lease obligations resulting from cash payments under finance leases. (b) Represents the Southern Company parent entity. (c) Represents reductions in affiliate finance lease obligations at Georgia Power, which are eliminated in Southern Company's consolidated financial statements.
Shares Used to Compute Diluted Earnings Per Share	Shares used to compute diluted earnings per share were as follows: Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) As reported shares 1,048 1,023 1,043 1,016 Effect of stock-based compensation 9 6 8 5 Diluted shares 1,057 1,029 1,051 1,021

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Pension Plans and Postretirement Plans	Components of the net periodic benefit costs for the three and nine months ended September 30, 2019 and 2018 are presented in the following tables. Three Months Ended September 30, 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 $ 7 Interest cost 123 28 38 6 1 9 Expected return on plan assets (222 ) (51 ) (73 ) (10 ) (2 ) (15 ) Amortization: Prior service costs 1 — — — — (1 ) Regulatory asset — — — — — 3 Net (gain)/loss 30 9 11 1 — 1 Net periodic pension cost (income) $ 5 $ 3 $ (5 ) $ — $ 1 $ 4 Postretirement Benefits Service cost $ 5 $ 1 $ 2 $ 1 $ — $ — Interest cost 18 4 6 — — 2 Expected return on plan assets (16 ) (6 ) (7 ) — — (1 ) Amortization: Prior service costs — 1 — — — — Regulatory asset — — — — — 1 Net (gain)/loss (1 ) — 1 — — — Net periodic postretirement benefit cost $ 6 $ — $ 2 $ 1 $ — $ 2 Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 219 $ 51 $ 56 $ 9 $ 5 $ 19 Interest cost 369 85 116 17 4 27 Expected return on plan assets (664 ) (154 ) (219 ) (30 ) (7 ) (45 ) Amortization: Prior service costs 2 1 1 — — (2 ) Regulatory asset — — — — — 10 Net (gain)/loss 90 27 33 4 — 2 Net periodic pension cost (income) $ 16 $ 10 $ (13 ) $ — $ 2 $ 11 Postretirement Benefits Service cost $ 14 $ 3 $ 4 $ 1 $ — $ 1 Interest cost 52 12 19 2 — 7 Expected return on plan assets (49 ) (19 ) (19 ) (1 ) — (4 ) Amortization: Prior service costs 2 3 — — — — Regulatory asset — — — — — 4 Net (gain)/loss (2 ) — 1 — — (2 ) Net periodic postretirement benefit cost $ 17 $ (1 ) $ 5 $ 2 $ — $ 6 Three Months Ended September 30, 2018 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 90 $ 19 $ 22 $ 5 $ 3 $ 8 Interest cost 116 26 34 5 1 10 Expected return on plan assets (236 ) (51 ) (74 ) (11 ) (3 ) (18 ) Amortization: Prior service costs 1 — 1 — — (1 ) Regulatory asset — — — — — 4 Net (gain)/loss 53 13 18 3 — 3 Net periodic pension cost (income) $ 24 $ 7 $ 1 $ 2 $ 1 $ 6 Postretirement Benefits Service cost $ 6 $ 1 $ 2 $ — $ 1 $ — Interest cost 19 5 7 — — 2 Expected return on plan assets (17 ) (7 ) (6 ) — — (1 ) Amortization: Prior service costs 2 1 — — — — Regulatory asset — — — — — 2 Net (gain)/loss 3 — 2 — — — Net periodic postretirement benefit cost $ 13 $ — $ 5 $ — $ 1 $ 3 Nine Months Ended September 30, 2018 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Pension Plans Service cost $ 269 $ 58 $ 65 $ 13 $ 7 $ 24 Interest cost 348 76 104 15 4 29 Expected return on plan assets (707 ) (155 ) (222 ) (31 ) (8 ) (53 ) Amortization: Prior service costs 3 1 2 — — (2 ) Regulatory asset — — — — — 11 Net (gain)/loss 160 40 52 8 1 9 Net periodic pension cost (income) $ 73 $ 20 $ 1 $ 5 $ 4 $ 18 Postretirement Benefits Service cost $ 18 $ 4 $ 5 $ 1 $ 1 $ 1 Interest cost 56 13 21 2 — 7 Expected return on plan assets (51 ) (20 ) (19 ) (1 ) — (5 ) Amortization: Prior service costs 5 3 1 — — — Regulatory asset — — — — — 5 Net (gain)/loss 10 1 6 — — — Net periodic postretirement benefit cost $ 38 $ 1 $ 14 $ 2 $ 1 $ 8

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	As of September 30, 2019 , assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows: Fair Value Measurements Using: As of September 30, 2019: 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) $ 297 $ 156 $ 34 $ — $ 487 Interest rate derivatives — 2 — — 2 Investments in trusts: (b)(c) Domestic equity 713 126 — — 839 Foreign equity 61 204 — — 265 U.S. Treasury and government agency securities — 301 — — 301 Municipal bonds — 86 — — 86 Pooled funds – fixed income — 16 — — 16 Corporate bonds 24 306 — — 330 Mortgage and asset backed securities — 82 — — 82 Private equity — — — 53 53 Cash and cash equivalents 1 — — — 1 Other 17 6 — — 23 Cash equivalents 2,078 7 — — 2,085 Other investments 9 15 — — 24 Total $ 3,200 $ 1,307 $ 34 $ 53 $ 4,594 Liabilities: Energy-related derivatives (a) $ 412 $ 227 $ 28 $ — $ 667 Interest rate derivatives — 72 — — 72 Foreign currency derivatives — 32 — — 32 Contingent consideration — — 21 — 21 Total $ 412 $ 331 $ 49 $ — $ 792 Fair Value Measurements Using: As of September 30, 2019: 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 464 114 — — 578 Foreign equity 61 60 — — 121 U.S. Treasury and government agency securities — 23 — — 23 Municipal bonds — 1 — — 1 Corporate bonds 24 142 — — 166 Mortgage and asset backed securities — 26 — — 26 Private equity — — — 53 53 Other 5 — — — 5 Cash equivalents 1,136 7 — — 1,143 Other investments 15 — — 15 Total $ 1,690 $ 393 $ — $ 53 $ 2,136 Liabilities: Energy-related derivatives $ — $ 22 $ — $ — $ 22 Georgia Power Assets: Energy-related derivatives $ — $ 3 $ — $ — $ 3 Nuclear decommissioning trusts: (b)(c) Domestic equity 248 1 — — 249 Foreign equity — 140 — — 140 U.S. Treasury and government agency securities — 277 — — 277 Municipal bonds — 86 — — 86 Corporate bonds — 164 — — 164 Mortgage and asset backed securities — 55 — — 55 Other 12 6 — — 18 Cash equivalents 392 — — — 392 Total $ 652 $ 732 $ — $ — $ 1,384 Liabilities: Energy-related derivatives $ — $ 49 $ — $ — $ 49 Interest rate derivatives — 60 — — 60 Total $ — $ 109 $ — $ — $ 109 Fair Value Measurements Using: As of September 30, 2019: 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 $ — $ 2 $ — $ — $ 2 Cash equivalents 234 — — — 234 Total $ 234 $ 2 $ — $ — $ 236 Liabilities: Energy-related derivatives $ — $ 24 $ — $ — $ 24 Southern Power Assets: Cash equivalents $ 23 $ — $ — $ — $ 23 Liabilities: Energy-related derivatives $ — $ 4 $ — $ — $ 4 Foreign currency derivatives — 32 — — 32 Contingent consideration — — 21 — 21 Total $ — $ 36 $ 21 $ — $ 57 Southern Company Gas Assets: Energy-related derivatives (a) $ 297 $ 146 $ 34 $ — $ 477 Non-qualified deferred compensation trusts: Domestic equity — 11 — — 11 Foreign equity — 4 — — 4 Pooled funds – fixed income — 16 — — 16 Cash equivalents 1 — — — 1 Total $ 298 $ 177 $ 34 $ — $ 509 Liabilities: Energy-related derivatives (a) $ 412 $ 128 $ 28 $ — $ 568 Interest rate derivatives — 5 — — 5 Total $ 412 $ 133 $ 28 $ — $ 573 (a) Energy-related derivatives exclude cash collateral of $166 million . (b) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information. (c) Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of September 30, 2019 , approximately $50 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan to creditors under the funds' managers' securities lending program. See Note 6 to the financial statements in Item 8 of the Form 10-K for additional information.
Schedule of Increase (Decrease) In Fair Value Of Funds	The fair value of the funds, including reinvested interest and dividends and excluding the funds' expenses, increased (decreased) by the amounts shown in the table below for the three and nine months ended September 30, 2019 and 2018. The changes were recorded as a change to the regulatory assets and liabilities related to AROs for Georgia Power and Alabama Power, respectively. Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in millions) Southern Company $ 27 $ 58 $ 255 $ 68 Alabama Power 15 39 140 49 Georgia Power 12 19 115 19
Financial Instruments for Which Carrying Amount Did Not Equal Fair Value	As of September 30, 2019 , 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 $ 45,182 $ 8,516 $ 11,787 $ 1,616 $ 4,960 $ 5,755 Fair value 49,424 9,646 13,001 1,717 5,290 6,489 (*) The long-term debt of Southern Company Gas is recorded at amortized cost, including the fair value adjustments at the effective date of the 2016 merger with Southern Company. Southern Company Gas amortizes the fair value adjustments over the lives of the respective bonds.
Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component	The following table includes transfers to Level 3, which represent the fair value of Southern Company Gas' commodity derivative contracts that include a significant unobservable component for the first time during the period. Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 (in millions) Beginning balance $ (10 ) $ — Transfers to Level 3 — (33 ) Transfers from Level 3 3 3 Instruments realized or otherwise settled during period (2 ) (2 ) Changes in fair value 14 37 Ending balance $ 5 $ 5

Derivatives (Tables)

Derivatives (Tables)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Energy-Related Derivatives	At September 30, 2019 , 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 (*) 475 2023 2029 Alabama Power 89 2022 — Georgia Power 184 2023 — Mississippi Power 99 2023 — Southern Power 9 2020 — Southern Company Gas (*) 94 2022 2029 (*) 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 4.1 billion mmBtu and short natural gas positions of 4.1 billion mmBtu as of September 30, 2019 , which is also included in Southern Company's total volume.
Schedule of Interest Rate Derivatives	At September 30, 2019 , 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 September 30, 2019 (in millions) (in millions) Cash Flow Hedges of Forecasted Debt Georgia Power $ 250 3-month LIBOR 2.23% March 2025 $ (9 ) Georgia Power 250 3-month LIBOR 2.40% March 2030 (20 ) Georgia Power 250 3-month LIBOR 2.48% February 2044 (30 ) Southern Company Gas 200 3-month LIBOR 1.81% September 2030 (5 ) Fair Value Hedges of Existing Debt Southern Company (*) 300 2.75% 3-month LIBOR+0.92% June 2020 (1 ) Southern Company (*) 1,500 2.35% 1-month LIBOR+0.87% July 2021 (5 ) Georgia Power 200 4.25% 3-month LIBOR+2.46% December 2019 (1 ) Southern Company Consolidated $ 2,950 $ (71 ) (*) Represents the Southern Company parent entity.
Schedule of Foreign Currency Derivatives	At September 30, 2019 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value Gain (Loss) at September 30, 2019 (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ (21 ) Southern Power 564 3.78% 500 1.85% June 2026 (11 ) Total $ 1,241 € 1,100 $ (32 )
Fair Value of Energy-Related Derivatives and Interest Rate Derivatives	The fair value of energy-related derivatives, interest rate derivatives, and foreign currency derivatives was reflected in the balance sheets as follows: As of September 30, 2019 As of December 31, 2018 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 $ 5 $ 61 $ 8 $ 23 Other deferred charges and assets/Other deferred credits and liabilities 6 44 9 26 Assets held for sale, current/Liabilities held for sale, current — 6 Total derivatives designated as hedging instruments for regulatory purposes $ 11 $ 105 $ 17 $ 55 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ — $ 8 $ 3 $ 7 Other deferred charges and assets/Other deferred credits and liabilities — 1 1 2 Interest rate derivatives: Other current assets/Other current liabilities — 72 — 19 Other deferred charges and assets/Other deferred credits and liabilities 2 — — 30 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 23 Other deferred charges and assets/Other deferred credits and liabilities — 8 75 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 2 $ 113 $ 79 $ 81 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 311 $ 342 $ 561 $ 575 Other deferred charges and assets/Other deferred credits and liabilities 165 211 180 325 Total derivatives not designated as hedging instruments $ 476 $ 553 $ 741 $ 900 Gross amounts recognized $ 489 $ 771 $ 837 $ 1,036 Gross amounts offset (a) $ (348 ) $ (514 ) $ (524 ) $ (801 ) Net amounts recognized in the Balance Sheets (b) $ 141 $ 257 $ 313 $ 235 As of September 30, 2019 As of December 31, 2018 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 $ 12 $ 3 $ 4 Other deferred charges and assets/Other deferred credits and liabilities 2 10 3 6 Total derivatives designated as hedging instruments for regulatory purposes $ 5 $ 22 $ 6 $ 10 Gross amounts recognized $ 5 $ 22 $ 6 $ 10 Gross amounts offset $ (2 ) $ (2 ) $ (4 ) $ (4 ) Net amounts recognized in the Balance Sheets $ 3 $ 20 $ 2 $ 6 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 27 $ 2 $ 8 Other deferred charges and assets/Other deferred credits and liabilities 2 22 4 13 Total derivatives designated as hedging instruments for regulatory purposes $ 3 $ 49 $ 6 $ 21 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ — $ 60 $ — $ 2 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 60 $ — $ 2 Gross amounts recognized $ 3 $ 109 $ 6 $ 23 Gross amounts offset $ (3 ) $ (3 ) $ (6 ) $ (6 ) Net amounts recognized in the Balance Sheets $ — $ 106 $ — $ 17 As of September 30, 2019 As of December 31, 2018 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 $ — $ 12 $ 1 $ 3 Other deferred charges and assets/Other deferred credits and liabilities 2 12 2 6 Total derivatives designated as hedging instruments for regulatory purposes $ 2 $ 24 $ 3 $ 9 Gross amounts recognized $ 2 $ 24 $ 3 $ 9 Gross amounts offset $ (2 ) $ (2 ) $ (2 ) $ (2 ) Net amounts recognized in the Balance Sheets $ — $ 22 $ 1 $ 7 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ — $ 4 $ 3 $ 6 Other deferred charges and assets/Other deferred credits and liabilities — — 1 2 Foreign currency derivatives: Other current assets/Other current liabilities — 24 — 23 Other deferred charges and assets/Other deferred credits and liabilities — 8 75 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 36 $ 79 $ 31 Gross amounts recognized $ — $ 36 $ 79 $ 31 Gross amounts offset $ — $ — $ (3 ) $ (3 ) Net amounts recognized in the Balance Sheets $ — $ 36 $ 76 $ 28 As of September 30, 2019 As of December 31, 2018 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 $ 1 $ 10 $ 2 $ 8 Other deferred charges and assets/Other deferred credits and liabilities — — — 1 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 10 $ 2 $ 9 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ — $ 4 $ — $ 1 Other deferred charges and assets/Other deferred credits and liabilities — 1 — — Interest rate derivatives: Assets from risk management activities/Liabilities from risk management activities-current — 5 — — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ — $ 10 $ — $ 1 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 311 $ 342 $ 559 $ 574 Other deferred charges and assets/Other deferred credits and liabilities 165 211 180 325 Total derivatives not designated as hedging instruments $ 476 $ 553 $ 739 $ 899 Gross amounts of recognized $ 477 $ 573 $ 741 $ 909 Gross amounts offset (a) $ (341 ) $ (507 ) $ (508 ) $ (785 ) Net amounts recognized in the Balance Sheets (b) $ 136 $ 66 $ 233 $ 124 (a) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $166 million and $277 million as of September 30, 2019 and December 31, 2018 , respectively. (b) Net amounts of derivative instruments outstanding exclude premium and intrinsic value associated with weather derivatives of $8 million as of December 31, 2018 .
Pre-tax Effects of Unrealized Derivative Gains (Losses) Arising from Energy-Related Derivative Instruments	At September 30, 2019 and December 31, 2018 , 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 September 30, 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 $ (55 ) $ (11 ) $ (27 ) $ (12 ) $ (5 ) Other regulatory assets, deferred (37 ) (8 ) (19 ) (10 ) — Other regulatory liabilities, current 6 3 — — 3 Total energy-related derivative gains (losses) $ (86 ) $ (16 ) $ (46 ) $ (22 ) $ (2 ) (*) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $8 million at September 30, 2019 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2018 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 $ (19 ) $ (3 ) $ (6 ) $ (2 ) $ (8 ) Other regulatory assets, deferred (16 ) (3 ) (9 ) (4 ) — Assets held for sale, current (6 ) — — — — Other regulatory liabilities, current 1 — — — 1 Total energy-related derivative gains (losses) $ (40 ) $ (6 ) $ (15 ) $ (6 ) $ (7 )
Pre-tax Effects of Interest Rate Derivatives, Designated as Cash Flow Hedging Instruments	For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of cash flow hedge accounting on accumulated OCI were as follows: Gain (Loss) Recognized in OCI on Derivative For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) (in millions) Southern Company Energy-related derivatives $ (5 ) $ (5 ) $ (11 ) $ 7 Interest rate derivatives (52 ) — (88 ) (2 ) Foreign currency derivatives (68 ) (10 ) (107 ) (31 ) Total $ (125 ) $ (15 ) $ (206 ) $ (26 ) Georgia Power Interest rate derivatives $ (47 ) $ — $ (83 ) $ — Total $ (47 ) $ — $ (83 ) $ — Southern Power Energy-related derivatives $ (3 ) $ (5 ) $ (5 ) $ 5 Foreign currency derivatives (68 ) (10 ) (107 ) (31 ) Total $ (71 ) $ (15 ) $ (112 ) $ (26 )
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location	For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of cash flow and fair value hedge accounting on income were as follows: Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) (in millions) Southern Company Total depreciation and amortization $ 760 $ 787 $ 2,267 $ 2,338 Gain (loss) on energy-related cash flow hedges (a) (1 ) — (5 ) 2 Total interest expense, net of amounts capitalized (434 ) (458 ) (1,294 ) (1,386 ) Gain (loss) on interest rate cash flow hedges (a) (5 ) (5 ) (14 ) (16 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) (18 ) (18 ) Gain (loss) on interest rate fair value hedges (b) 10 (4 ) 43 (35 ) Total other income (expense), net 61 57 239 195 Gain (loss) on foreign currency cash flow hedges (a)(c) (54 ) (9 ) (62 ) (46 ) Southern Power Total depreciation and amortization $ 120 $ 130 $ 357 $ 370 Gain (loss) on energy-related cash flow hedges (a) (1 ) — (5 ) 2 Total interest expense, net of amounts capitalized (43 ) (45 ) (127 ) (138 ) Gain (loss) on foreign currency cash flow hedges (a) (6 ) (6 ) (18 ) (18 ) Total other income (expense), net 6 17 48 22 Gain (loss) on foreign currency cash flow hedges (a)(c) (54 ) (9 ) (62 ) (46 ) (a) Reclassified from accumulated OCI into earnings. (b) For fair value hedges, changes in the fair value of the derivative contracts are generally equal to changes in the fair value of the underlying debt and have no material impact on income. (c) The reclassification from accumulated OCI into other income (expense), net completely offsets currency gains and losses arising from changes in the U.S. currency exchange rates used to record the euro-denominated notes.
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location	As of September 30, 2019 and December 31, 2018, the following amounts were recorded on the balance sheets related to cumulative basis adjustments for fair value hedges: Carrying Amount of the Hedged Item Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item Balance Sheet Location of Hedged Items As of September 30, 2019 As of December 31, 2018 As of September 30, 2019 As of December 31, 2018 (in millions) (in millions) Southern Company Securities due within one year $ (500 ) $ (498 ) $ — $ 2 Long-term debt (2,093 ) (2,052 ) (2 ) 41 Georgia Power Securities due within one year $ (500 ) $ (498 ) $ — $ 2
Pre-tax Effect of Interest Rate and Energy Related Derivatives	For the three and nine months ended September 30, 2019 and 2018 , the pre-tax effects of energy-related derivatives not designated as hedging instruments on the statements of income of Southern Company and Southern Company Gas were as follows: Gain (Loss) Three Months Ended September 30, Nine Months Ended September 30, Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2019 2018 2019 2018 (in millions) (in millions) Energy-related derivatives: Natural gas revenues (*) $ (2 ) $ (36 ) $ 81 $ (79 ) Cost of natural gas 2 2 5 5 Total derivatives in non-designated hedging relationships $ — $ (34 ) $ 86 $ (74 ) (*) Excludes immaterial gains (losses) recorded in natural gas revenues associated with weather derivatives for all periods presented.

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	During the third quarter 2019 , Southern Power acquired a controlling interest in the fuel cell generation facility listed below. Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller Approximate Nameplate Capacity (MW) Location Southern Power Percentage Ownership COD PPA Remaining Period DSGP (a) Fuel Cell Bloom Energy 28 Delaware 100% of Class B N/A (b) 15 years (a) During the second and third quarters 2019, Southern Power made a total investment of approximately $166 million in DSGP and now holds a controlling interest and consolidates 100% of DSGP's operating results. Southern Power records net income attributable to noncontrolling interests for approximately 10 MWs of the facility. (b) Approximately 18 MWs of the 28 -MW facility was repowered between June and August 2019.
Schedule of Construction Projects	Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Nine Months Ended September 30, 2019 Mankato expansion (a) Natural Gas 385 Mankato, MN May 2019 20 years Projects Under Construction as of September 30, 2019 Wildhorse Mountain (b) Wind 100 Pushmataha County, OK Fourth quarter 2019 20 years Reading (c) Wind 200 Osage and Lyon Counties, KS Second quarter 2020 12 years (a) Southern Power has an agreement with a subsidiary of Xcel to sell all of its equity interests in Plant Mankato, including the expansion. The transaction is subject to FERC approval and is expected to close by January 20, 2020. The expansion unit started providing energy under a PPA with Northern States Power on June 1, 2019. See " Sales of Natural Gas and Biomass Plants " below. (b) In May 2018, Southern Power purchased 100% of the Wildhorse Mountain facility. Southern Power entered into a tax equity partnership in June 2019 with funding of tax equity amounts expected to occur upon commercial operation. (c) In August 2018, Southern Power purchased 100% of the membership interests of the Reading facility from the joint development arrangement with Renewable Energy Systems Americas, Inc. Southern Power may enter into a tax equity partnership, in which case it would then own 100% of the class B membership interests.
Disposal Groups, Including Discontinued Operations	Gulf Power and Southern Power's equity interests in Plant Oleander and Plant Stanton Unit A (together, the Florida Plants) and Plant Nacogdoches represented individually significant components of Southern Company and Southern Power, respectively; therefore, pre-tax profit for these components for the three and nine months ended September 30, 2019 and 2018 is presented below: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (in millions) Earnings before income taxes: Gulf Power $ — $ 59 $ — $ 146 Southern Power's Florida Plants $ — $ 18 $ — $ 40 Southern Power's Plant Nacogdoches (*) $ — $ 7 $ 16 $ 20 (*) Earnings before income taxes for Plant Nacogdoches for the nine months ended September 30, 2019 represents January 1, 2019 through June 13, 2019 (the divestiture date). The following table provides Southern Company's and Southern Power's major classes of assets and liabilities classified as held for sale at September 30, 2019 and December 31, 2018 : Southern Company Southern Power (in millions) At September 30, 2019 Assets Held for Sale: Current assets $ 17 $ 12 Total property, plant, and equipment 551 546 Goodwill and other intangible assets 40 40 Other non-current assets 40 14 Total Assets Held for Sale $ 648 $ 612 Liabilities Held for Sale: Current liabilities $ 6 $ 3 Other non-current liabilities 20 — Total Liabilities Held for Sale $ 26 $ 3 At December 31, 2018 Assets Held for Sale: Current assets $ 393 $ 8 Total property, plant, and equipment 4,583 536 Other intangible assets 40 40 Other non-current assets 727 — Total Assets Held for Sale $ 5,743 $ 584 Liabilities Held for Sale: Current liabilities $ 425 $ 15 Long-term debt 1,286 — Accumulated deferred income taxes 618 — Other non-current liabilities 932 — Total Liabilities Held for Sale $ 3,261 $ 15

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Major Categories of Lease Obligations	The major categories of lease obligations are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Electric generating units $ 988 $ 125 $ 1,488 $ — $ — $ — Real estate/land 785 4 57 2 395 77 Communication towers 150 2 3 — — 13 Railcars 51 23 25 3 — — Other 89 9 14 2 — 1 Total $ 2,063 $ 163 $ 1,587 $ 7 $ 395 $ 91
Balance Sheet Amounts Recorded for Operating and Financing Leases	Balance sheet amounts recorded for operating and finance leases are as follows: As of September 30, 2019 Southern Company (*) Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Operating Leases Operating lease ROU assets, net $ 1,823 $ 143 $ 1,461 $ 7 $ 368 $ 92 Operating lease obligations - current $ 229 $ 49 $ 143 $ 2 $ 22 $ 14 Operating lease obligations - non current 1,606 109 1,287 5 373 77 Total operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance Leases Finance lease ROU assets, net $ 220 $ 4 $ 134 $ — $ — $ — Finance lease obligations - current $ 21 $ 1 $ 12 $ — $ — $ — Finance lease obligations - noncurrent 207 4 145 — — — Total finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ — (*) Includes operating lease ROU assets, net and operating lease obligations classified as held for sale.
Lease Costs and Other Information	Lease costs for the three and nine months ended September 30, 2019 , which includes both amounts recognized as operations and maintenance expense and amounts capitalized as part of the cost of another asset, are as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease cost Operating lease cost $ 94 $ 29 $ 53 $ 1 $ 7 $ 5 Finance lease cost: Amortization of ROU assets 7 — 4 — — — Interest on lease obligations 3 — 4 — — — Total finance lease cost 10 — 8 — — — Short-term lease costs 9 4 5 — — — Variable lease cost 33 4 26 — 1 — Total lease cost $ 146 $ 37 $ 92 $ 1 $ 8 $ 5 For the Nine Months Ended September 30, 2019 Lease cost Operating lease cost $ 243 $ 49 $ 154 $ 2 $ 21 $ 14 Finance lease cost: Amortization of ROU assets 21 1 11 — — — Interest on lease obligations 9 — 14 — — — Total finance lease cost 30 1 25 — — — Short-term lease costs 39 15 17 — — — Variable lease cost 81 6 67 — 3 — Sublease income (1 ) (1 ) — — — — Total lease cost $ 392 $ 70 $ 263 $ 2 $ 24 $ 14 Georgia Power has variable lease payments that are based on the amount of energy produced by certain renewable generating facilities subject to PPAs. Other information with respect to cash and noncash activities related to leases, as well as weighted-average lease terms and discount rates, is as follows: For the Nine Months Ended September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Other information Cash paid for amounts included in the measurements of lease obligations: Operating cash flows from operating leases $ 211 $ 50 $ 130 $ 2 $ 18 $ 13 Operating cash flows from finance leases 3 1 17 — — — Financing cash flows from finance leases 24 — 4 — — — ROU assets obtained in exchange for new operating lease obligations 76 7 18 — — 14 ROU assets obtained in exchange for new finance lease obligations 31 1 24 — — — As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas Weighted-average remaining lease term in years: Operating leases 14.4 3.4 10.4 6.8 33.2 9.6 Finance leases 18.9 12.4 10.8 N/A N/A N/A Weighted-average discount rate: Operating leases 4.56 % 3.33 % 4.46 % 3.98 % 5.68 % 3.73 % Finance leases 5.07 % 3.65 % 10.74 % N/A N/A N/A
Maturities of Operating Lease Liabilities	Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ —
Maturities of Finance Lease Liabilities	Maturities of lease liabilities are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) Maturity Analysis Operating leases: 2019 (remaining) $ 45 $ 4 $ 23 $ 1 $ 8 $ 4 2020 284 54 205 2 22 17 2021 269 53 198 1 23 17 2022 259 52 196 1 23 13 2023 202 4 197 1 24 11 Thereafter 1,662 2 991 2 847 49 Total 2,721 169 1,810 8 947 111 Less: Present value discount 886 11 380 1 552 20 Operating lease obligations $ 1,835 $ 158 $ 1,430 $ 7 $ 395 $ 91 Finance leases: 2019 (remaining) $ 9 $ — $ 4 $ — $ — $ — 2020 31 1 28 — — — 2021 24 1 24 — — — 2022 21 1 24 — — — 2023 17 1 25 — — — Thereafter 259 1 161 — — — Total 361 5 266 — — — Less: Present value discount 133 — 109 — Finance lease obligations $ 228 $ 5 $ 157 $ — $ — $ —
Leases Not Yet Commenced	As of September 30, 2019 , Alabama Power and Southern Power have additional operating leases that have not yet commenced, as detailed in the following table: Southern Company Alabama Power Southern Power Operating lease type PPAs and land PPAs Land Expected commencement date 2019-2024 2020-2024 2019-2022 Longest lease term expiration 28-31 years 28 years 31 years Estimated total obligations (in millions) $159 $95 $64
Lease Income, Sales-type Leases	Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26
Lease Income, Operating Leases	Lease income for the three and nine months ended September 30, 2019 is as follows: Southern Company Alabama Power Georgia Power Mississippi Power Southern Power Southern Company Gas (in millions) For the Three Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 2 $ — $ — $ 2 $ — $ — Lease income - operating leases 64 6 18 — 31 9 Variable lease income 141 — — — 151 — Total lease income $ 207 $ 6 $ 18 $ 2 $ 182 $ 9 For the Nine Months Ended September 30, 2019 Lease income - interest income on sales-type leases $ 7 $ — $ — $ 7 $ — $ — Lease income - operating leases 216 19 57 — 111 26 Variable lease income 324 — — — 349 — Total lease income $ 547 $ 19 $ 57 $ 7 $ 460 $ 26
Undiscounted Cash Flows to be Received Under Tolling Arrangements Accounted for as Sales-type Leases	The undiscounted cash flows to be received under tolling arrangements accounted for as sales-type leases are as follows: As of September 30, 2019 Southern Company Mississippi Power (in millions) 2019 (remaining) $ 4 $ 4 2020 17 17 2021 15 15 2022 15 15 2023 14 14 Thereafter 152 152 Total undiscounted cash flows $ 217 $ 217 Lease receivable 119 119 Difference between undiscounted cash flows and discounted cash flows $ 98 $ 98
Undiscounted Cash Flows to be Received Under PPAs Accounted for as Operating Leases	The undiscounted cash flows to be received under operating leases and contracts accounted for as operating leases (adjusted for intercompany eliminations) are as follows: As of September 30, 2019 Southern Company Alabama Power Georgia Power Southern Power Southern Company Gas (in millions) 2019 (remaining) $ 39 $ 6 $ 7 $ 8 $ 9 2020 155 26 26 65 35 2021 140 22 18 66 35 2022 121 13 8 68 34 2023 109 5 2 69 34 Thereafter 1,166 22 — 350 497 Total $ 1,730 $ 94 $ 61 $ 626 $ 644

Segment and Related Informati_2

Segment and Related Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Financial Data for Business Segments	Financial data for business segments and products and services for the three and nine months ended September 30, 2019 and 2018 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 September 30, 2019 Operating revenues $ 4,908 $ 574 $ (119 ) $ 5,363 $ 498 $ 146 $ (12 ) $ 5,995 Segment net income (loss) (a)(b)(c)(d) 1,373 86 — 1,459 (29 ) (110 ) (4 ) 1,316 Nine Months Ended September 30, 2019 Operating revenues $ 12,252 $ 1,527 $ (331 ) $ 13,448 $ 2,661 $ 514 $ (118 ) $ 16,505 Segment net income (loss) (a)(b)(c)(d)(e) 2,719 316 — 3,035 347 931 (15 ) 4,298 At September 30, 2019 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 263 $ — $ 5,280 Total assets 80,493 14,397 (756 ) 94,134 21,047 3,569 (1,159 ) 117,591 Three Months Ended September 30, 2018 Operating revenues $ 5,014 $ 635 $ (140 ) $ 5,509 $ 492 $ 202 $ (44 ) $ 6,159 Segment net income (loss) (a)(b)(e)(f) 1,148 92 — 1,240 46 (119 ) (3 ) 1,164 Nine Months Ended September 30, 2018 Operating revenues $ 13,117 $ 1,699 $ (360 ) $ 14,456 $ 2,861 $ 984 $ (143 ) $ 18,158 Segment net income (loss) (a)(b)(e)(f) 1,711 235 — 1,946 294 (292 ) — 1,948 At December 31, 2018 Goodwill $ — $ 2 $ — $ 2 $ 5,015 $ 298 $ — $ 5,315 Total assets 79,382 14,883 (306 ) 93,959 21,448 3,285 (1,778 ) 116,914 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes pre-tax charges for estimated losses on plants under construction of $4 million ( $3 million after tax) and $1 million ( $1 million after tax) for the three months ended September 30, 2019 and 2018 , respectively, and $10 million ( $7 million after tax) and $1.1 billion ( $0.8 billion after tax) for the nine months ended September 30, 2019 and 2018 , respectively. See Note 2 to the financial statements in Item 8 of the Form 10-K and Note (B) under "Georgia Power – Nuclear Construction" and " Mississippi Power – Kemper County Energy Facility " 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 nine months ended September 30, 2019 , of which $4 million ( $4 million after tax) was recorded in the three months ended September 30, 2019 , as well as impairment charges in contemplation of the sales of two of PowerSecure's business units totaling $18 million and $50 million for the three and nine months ended September 30, 2019 , respectively. See Note (K) under " Southern Company " for additional information. (d) Segment net income (loss) for Southern Company Gas includes a pre-tax impairment charge of $92 million ( $65 million after tax) related to a natural gas storage facility in Louisiana. See Note (C) under "Other Matters – Southern Company Gas" for additional information. (e) Segment net income (loss) for Southern Power includes a $23 million pre-tax gain ( $88 million gain after tax) on the sale of Plant Nacogdoches for the nine months ended September 30, 2019 and pre-tax impairment charges of $36 million ( $27 million after tax) and $155 million ( $116 million after tax) for the three and nine months ended September 30, 2018 , respectively. See Note (K) under " Southern Power " and Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Power – Development Projects" and " – Sale of Natural Gas Plants" for additional information. (f) Segment net income (loss) for Southern Company Gas includes a net gain on dispositions of $353 million ( $40 million gain after tax) and $317 million ( $35 million loss after tax) for the three and nine months ended September 30, 2018, respectively, related to the Southern Company Gas Dispositions and a goodwill impairment charge of $42 million for the nine months ended September 30, 2018 related to the sale of Pivotal Home Solutions. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. Business segment financial data for the three and nine months ended September 30, 2019 and 2018 was as follows: Gas Distribution Operations (a) Gas Pipeline Investments Wholesale Gas Services (b) Gas Marketing Services (c)(d) Total All Other (e) Eliminations Consolidated (in millions) Three Months Ended September 30, 2019 Operating revenues $ 448 $ 8 $ (2 ) $ 39 $ 493 $ 10 $ (5 ) $ 498 Segment net income (loss) 37 6 (9 ) (4 ) 30 (59 ) — (29 ) Nine Months Ended September 30, 2019 Operating revenues $ 2,188 $ 24 $ 132 $ 326 $ 2,670 $ 34 $ (43 ) $ 2,661 Segment net income (loss) 228 63 61 54 406 (59 ) — 347 Total assets at September 30, 2019 17,798 1,743 657 1,443 21,641 10,429 (11,023 ) 21,047 Three Months Ended September 30, 2018 Operating revenues $ 441 $ 8 $ (8 ) $ 44 $ 485 $ 13 $ (6 ) $ 492 Segment net income (loss) 74 20 (18 ) (8 ) 68 (22 ) — 46 Nine Months Ended September 30, 2018 Operating revenues $ 2,297 $ 24 $ 142 $ 403 $ 2,866 $ 39 $ (44 ) $ 2,861 Segment net income (loss) 290 68 65 (71 ) 352 (58 ) — 294 Total assets at December 31, 2018 17,266 1,763 1,302 1,587 21,918 11,112 (11,582 ) 21,448 (a) Operating revenues for the three gas distribution operations dispositions were $8 million and $245 million for the three and nine months ended September 30, 2018 , respectively. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. (b) The revenues for wholesale gas services are netted with costs associated with its energy and risk management activities. A reconciliation of operating revenues and intercompany revenues is shown in the following table. Third Party Gross Revenues Intercompany Revenues Total Gross Revenues Less Gross Gas Costs Operating Revenues (in millions) Three Months Ended September 30, 2019 $ 1,138 $ 72 $ 1,210 $ 1,212 $ (2 ) Three Months Ended September 30, 2018 1,573 82 1,655 1,663 (8 ) Nine Months Ended September 30, 2019 $ 4,287 $ 223 $ 4,510 $ 4,378 $ 132 Nine Months Ended September 30, 2018 4,847 352 5,199 5,057 142 (c) Operating revenues for Pivotal Home Solutions were $55 million for the nine months ended September 30, 2018 . See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information on the sale of Pivotal Home Solutions. (d) Segment net income (loss) for gas marketing services includes a loss on disposition of $34 million for the nine months ended September 30, 2018 and a goodwill impairment charge of $42 million for the nine months ended September 30, 2018 related to the sale of Pivotal Home Solutions. See Note 15 to the financial statements in Item 8 of the Form 10-K under "Southern Company Gas" for additional information. (e) Segment net income (loss) for the "All Other" column includes a pre-tax impairment charge of $92 million ( $65 million after tax) for the three and nine months ended September 30, 2019 related to a natural gas storage facility in Louisiana. See Note (C) under "Other Matters – Southern Company Gas" for additional information.
Financial Data for Products and Services	Products and Services Electric Utilities' Revenues Retail Wholesale Other Total (in millions) Three Months Ended September 30, 2019 $ 4,512 $ 625 $ 226 $ 5,363 Three Months Ended September 30, 2018 4,605 698 206 5,509 Nine Months Ended September 30, 2019 $ 11,136 $ 1,667 $ 645 $ 13,448 Nine Months Ended September 30, 2018 11,913 1,937 606 14,456 Southern Company Gas' Revenues Gas (a) Gas (b) Other Total (in millions) Three Months Ended September 30, 2019 $ 445 $ 39 $ 14 $ 498 Three Months Ended September 30, 2018 438 44 10 492 Nine Months Ended September 30, 2019 $ 2,169 $ 326 $ 166 $ 2,661 Nine Months Ended September 30, 2018 2,276 403 182 2,861 (a) Operating revenues for the three gas distribution operations dispositions were $7 million and $245 million for the three and nine months ended September 30, 2018 , respectively. (b) Operating revenues for Pivotal Home Solutions were $55 million for the nine months ended September 30, 2018 , respectively.

Introduction - Narrative (Detai

Introduction - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment charges	$ 18,000,000			$ 50,000,000
SOUTHERN Co GAS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Inventory decrement	0		$ 0	10,000,000	$ 0
Nicor Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Inventory decrement				0
ALABAMA POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ARO				$ 312,000,000
MISSISSIPPI POWER CO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ARO		$ 58,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure International, Inc.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment charges		$ 32,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure International, Inc. Lighting Business
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment charges	2,000,000
Intangible asset impairment	$ 3,000,000

Introduction - Goodwill (Detail

Introduction - Goodwill (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 5,280	$ 5,315
SOUTHERN Co GAS
Goodwill [Line Items]
Goodwill	5,015	5,015
SOUTHERN Co GAS | Gas Distribution Operations
Goodwill [Line Items]
Goodwill	4,034	4,034
SOUTHERN Co GAS | Gas Marketing Services
Goodwill [Line Items]
Goodwill	$ 981	$ 981

Introduction - Other Intangible

Introduction - Other Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other intangible assets subject to amortization:
Gross Carrying Amount	$ 740	$ 773
Accumulated Amortization	(265)	(235)
Other Intangible Assets, Net	475	538
Other intangible assets not subject to amortization:
Federal Communications Commission licenses	75	75
Total other intangible assets
Gross Carrying Amount	815	848
Other Intangible Assets, Net	550	613
Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	211	223
Accumulated Amortization	(110)	(94)
Other Intangible Assets, Net	101	129
Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	64	70
Accumulated Amortization	(23)	(21)
Other Intangible Assets, Net	41	49
Other
Other intangible assets subject to amortization:
Gross Carrying Amount	12	11
Accumulated Amortization	(8)	(5)
Other Intangible Assets, Net	4	6
SOUTHERN POWER CO
Other intangible assets subject to amortization:
Accumulated Amortization	(64)	(61)
SOUTHERN POWER CO | PPA fair value adjustments
Other intangible assets subject to amortization:
Gross Carrying Amount	389	405
Accumulated Amortization	(64)	(61)
Other Intangible Assets, Net	325	344
SOUTHERN Co GAS
Other intangible assets subject to amortization:
Gross Carrying Amount	246	246
Accumulated Amortization	(168)	(145)
Other Intangible Assets, Net	78	101
Total other intangible assets
Other Intangible Assets, Net	78	101
SOUTHERN Co GAS | Customer relationships
Other intangible assets subject to amortization:
Gross Carrying Amount	156	156
Accumulated Amortization	(99)	(84)
Other Intangible Assets, Net	57	72
SOUTHERN Co GAS | Trade names
Other intangible assets subject to amortization:
Gross Carrying Amount	26	26
Accumulated Amortization	(9)	(7)
Other Intangible Assets, Net	17	19
SOUTHERN Co GAS | Storage and transportation contracts
Other intangible assets subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(60)	(54)
Other Intangible Assets, Net	$ 4	$ 10

Introduction - Intangibles, Amo

Introduction - Intangibles, Amortization (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 14	$ 45
Decrease in operating revenues	6	20
SOUTHERN POWER CO
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	4	14
SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	7	23
Gas Marketing Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5	17
Wholesale Gas Services | SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 2	$ 6

Introduction - Restricted Cash

Introduction - Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 2,931	$ 1,396
Cash and cash equivalents held for sale		9
Restricted cash:
Total cash, cash equivalents, and restricted cash	2,935	1,519	$ 1,891	$ 2,147
Restricted cash
Restricted cash:
Restricted cash		0
Other accounts and notes receivable
Restricted cash:
Restricted cash	3	114
GEORGIA POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	449	4
Cash and cash equivalents held for sale		0
Restricted cash:
Total cash, cash equivalents, and restricted cash	449	112	380	852
GEORGIA POWER CO | Restricted cash
Restricted cash:
Restricted cash		108
GEORGIA POWER CO | Other accounts and notes receivable
Restricted cash:
Restricted cash		0
SOUTHERN Co GAS
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	59	64
Cash and cash equivalents held for sale		0
Restricted cash:
Total cash, cash equivalents, and restricted cash	62	70	$ 62	$ 78
SOUTHERN Co GAS | Restricted cash
Restricted cash:
Restricted cash		0
SOUTHERN Co GAS | Other accounts and notes receivable
Restricted cash:
Restricted cash	$ 3	$ 6

Introduction - Asset Retirement

Introduction - Asset Retirement Obligations (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2018	$ 9,394
Liabilities incurred	35
Liabilities settled	(223)
Accretion	299
Cash flow revisions	455
Balance at September 30, 2019	9,960
ALABAMA POWER CO
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2018	3,210
Liabilities incurred	0
Liabilities settled	(76)
Accretion	107
Cash flow revisions	312
Balance at September 30, 2019	3,553
MISSISSIPPI POWER CO
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at December 31, 2018	160
Liabilities incurred	1
Liabilities settled	(28)
Accretion	5
Cash flow revisions	57
Balance at September 30, 2019	$ 195

Regulatory Matters - Cost Recov

Regulatory Matters - Cost Recovery Clauses (Details) - USD ($) $ in Millions	Sep. 30, 2019	Feb. 05, 2019	Dec. 31, 2018
ALABAMA POWER CO
Loss Contingencies [Line Items]
Rate RSE Refund Liability		$ 75
ALABAMA POWER CO | Deferred under recovered regulatory clause revenues
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 0		$ 42
Rate CNP PPA	45		25
Retail Energy Cost Recovery	0		109
ALABAMA POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	55		0
Retail Energy Cost Recovery	21		0
Natural Disaster Reserve	23		20
GEORGIA POWER CO | Receivables – under recovered fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	0		115
GEORGIA POWER CO | Other deferred credits and liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	(1)		0
MISSISSIPPI POWER CO | Over recovered regulatory clause liabilities
Loss Contingencies [Line Items]
Fuel Cost Recovery	$ (18)		$ (8)

Regulatory Matters - Alabama Po

Regulatory Matters - Alabama Power (Details) - ALABAMA POWER CO $ in Millions	Oct. 01, 2019	Sep. 30, 2019USD ($)MW	Sep. 06, 2019MW	May 08, 2019MW	Apr. 15, 2019USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional generating capacity (in MWs)			200
Winter reserve capacity (in MWs)			2,400
Capital investment, amount | $		$ 1,100
PPA, additional generating capacity (in MWs)		640
Plant Barry Unit 8
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Approximate nameplate capacity (MW)				720
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Capitalized asset retirement costs, net | $					$ 700
Remaining amounts of regulatory assets for which no return on investment during recovery period is provided | $					700
Restatement Adjustment | Plant Gorgas Units 8, 9, and 10
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net investment costs | $					654
Remaining amounts of regulatory assets for which no return on investment during recovery period is provided | $					$ 654
Subsequent Event
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Regulatory asset, amortization period	5 years
Subsequent Event | Plant Barry Unit 8
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Costs incurred, percentage of estimated in-service costs	5.00%
2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
PPA, additional generating capacity (in MWs)		240
2022 through 2024
Error Corrections and Prior Period Adjustments Restatement [Line Items]
PPA, additional generating capacity (in MWs)		400

Regulatory Matters - Georgia Po

Regulatory Matters - Georgia Power (Details) - GEORGIA POWER CO $ in Millions	Sep. 24, 2019	Jul. 29, 2019MW	Jul. 16, 2019MW	Jun. 28, 2019	Sep. 30, 2019USD ($)MW	Dec. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2019USD ($)
Public Utilities, General Disclosures [Line Items]
Alternate Rate Plan period				3 years
Requested increases effective January 1, 2020					$ 560
Requested increases effective January 1, 2021					144
Requested increases effective January 1, 2022					233
Proposed retail ROE	10.90%
Proposed equity ratio	56.00%
Percentage of earnings above the top of allowed ROE range shared with customers				66.67%
Percentage of earnings above the top of allowed ROE range not shared with customers				33.33%
Cost recovery, new nuclear									$ 99
Cost recovery, estimate, nuclear fuel					50
Under recovered CCR compliance cost					$ 157
Rejected proposed capacity of units for certification | MW			25
Requested recovery of under recovered CCR compliance costs, period					3 years
Approved capacity of units for solar generation resources (mw) | MW					2,210
Approved capacity of units for investment portfolio (mw) | MW					80
Minimum
Public Utilities, General Disclosures [Line Items]
Allowed retail ROE				10.00%
Maximum
Public Utilities, General Disclosures [Line Items]
Allowed retail ROE				12.00%
Plant Hammond Units 1 Through 4
Public Utilities, General Disclosures [Line Items]
Capacity of units included in request for decertification of units (mw) | MW		840
Net book value of planned units retirements					$ 500
Plant McIntosh Unit 1
Public Utilities, General Disclosures [Line Items]
Capacity of units included in request for decertification of units (mw) | MW		142.5
Net book value of planned units retirements					40
Plant Hammond and Plant McIntosh Units
Public Utilities, General Disclosures [Line Items]
Net book value of planned units retirements					295
Plant Mitchell Unit 3
Public Utilities, General Disclosures [Line Items]
Net book value of planned units retirements					$ 8
Remaining Net Book Value Of Retired Assets | Maximum
Public Utilities, General Disclosures [Line Items]
Regulatory asset, amortization period					3 years
Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Recovery of estimated under recovered CCR rule costs						$ 655	$ 395	$ 277

Regulatory Matters - Requested

Regulatory Matters - Requested Recovery of Proposed Increases (Details) - GEORGIA POWER CO $ in Millions	Sep. 30, 2019USD ($)
Public Utilities, General Disclosures [Line Items]
2020	$ 560
2021	144
2022	233
Levelized
Public Utilities, General Disclosures [Line Items]
2020	210
2021	0
2022	0
CCR ARO
Public Utilities, General Disclosures [Line Items]
2020	158
2021	139
2022	227
Environmental Compliance Cost Recovery
Public Utilities, General Disclosures [Line Items]
2020	163
2021	0
2022	0
Demand-Side Management
Public Utilities, General Disclosures [Line Items]
2020	12
2021	1
2022	1
Municipal Franchise Fee
Public Utilities, General Disclosures [Line Items]
2020	17
2021	3
2022	$ 5

Regulatory Matters - Nuclear Co

Regulatory Matters - Nuclear Construction (Details) - GEORGIA POWER CO $ in Millions

Jan. 01, 2021

Jan. 01, 2020

Nov. 01, 2019USD ($)

Aug. 30, 2019USD ($)

Feb. 19, 2019USD ($)

Jan. 11, 2018USD ($)

Jan. 01, 2016

Mar. 31, 2019USD ($)

Dec. 31, 2018USD ($)appeal

Sep. 30, 2019USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2012utilityMW

Dec. 31, 2009USD ($)

Dec. 31, 2022USD ($)

Aug. 31, 2018

Dec. 31, 2014

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

$ 2,100

Increase (decrease) in NCCR tariff

$ 88

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

Requested capital construction costs

$ 1,200

$ 5,400

Deferred approval of expenditures related to administrative claim

21.5

$ 51.6

Refund of construction capital costs

$ 30.1

Scenario, Forecast

Loss Contingencies [Line Items]

Increase (decrease) in NCCR tariff

$ (65)

FFB Loan

Loss Contingencies [Line Items]

Long-term line of credit

$ 3,460

Eligible project costs to be reimbursed

$ 5,130

Plant Vogtle Units 3 And 4

Loss Contingencies [Line Items]

Proportionate ownership share

45.70%

Construction contingency estimate, subject to rate recovery evaluation

$ 30

Construction financing costs

2,100

Base project capital cost forecast, monthly

50

Monthly AFUDC

11

Percentage of ownership interest required for voting for continuing construction

90.00%

90.00%

Cost settlement agreement revised forecast, net of payments

$ 7,300

Public utilities, approved return on equity percentage

10.00%

Public utilities, approved return on equity, monthly percentage decrease

0.10%

Return on equity reduction, negative impact on earnings

$ 100

Guarantor obligations

$ 1,700

Customer refund

$ 188

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%

8.30%

Return on equity reduction, negative impact on earnings

$ 70

$ 650

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

Regulatory Matters - Nuclear _2

Regulatory Matters - Nuclear Construction Cost and Schedule (Details) - GEORGIA POWER CO - Plant Vogtle Units 3 And 4 $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Loss Contingencies [Line Items]
Base project capital cost forecast	$ 8,000
Construction contingency estimate	400
Total project capital cost forecast	8,400
Net investment as of September 30, 2019	(5,500)
Remaining estimate to complete	2,900
Expected capitalized costs	300
Guarantor obligations	1,700
Customer refund	$ 188

Regulatory Matters - Mississipp

Regulatory Matters - Mississippi Power (Details) - USD ($) $ in Millions	Jan. 01, 2019	Oct. 24, 2019
MISSISSIPPI POWER CO | MRA Revenue
Loss Contingencies [Line Items]
Decrease in base rate under cost based electric tariff	$ 3.7
Subsequent Event | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Proportionate ownership share		50.00%
Total estimated cost		$ 66
Subsequent Event | MISSISSIPPI POWER CO | Ash Pond Closure
Loss Contingencies [Line Items]
Total estimated cost		17
Subsequent Event | Mississippi Power And Gulf Power
Loss Contingencies [Line Items]
Total estimated cost		$ 125

Regulatory Matters - Kemper Cou

Regulatory Matters - Kemper County Energy Facility (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended	48 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2023
Loss Contingencies [Line Items]
Liabilities incurred				$ 35
MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Liabilities incurred				1
MISSISSIPPI POWER CO | Kemper IGCC
Loss Contingencies [Line Items]
Pre-tax charge to income			$ 4	10
Asset retirement obligation, liabilities incurred, net of tax			3	7
Asset retirement obligation, expected cost			$ 10	$ 10
Government grants received	$ 387
MISSISSIPPI POWER CO | Kemper IGCC | Scenario, Forecast
Loss Contingencies [Line Items]
Liabilities incurred		$ 3
MISSISSIPPI POWER CO | Kemper IGCC | Minimum | Scenario, Forecast
Loss Contingencies [Line Items]
Liabilities incurred					$ 2
MISSISSIPPI POWER CO | Kemper IGCC | Maximum | Scenario, Forecast
Loss Contingencies [Line Items]
Liabilities incurred					$ 7

Regulatory Matters - Southern C

Regulatory Matters - Southern Company Gas (Details) $ in Millions	Oct. 08, 2019USD ($)	Oct. 02, 2019	Sep. 25, 2019USD ($)	Jun. 03, 2019USD ($)	Apr. 16, 2019USD ($)intervenor	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Nov. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2017
Nicor Gas
Loss Contingencies [Line Items]
Approved increase (decrease) in fuel rates amount								$ 230
Public utilities, approved return on equity percentage					9.86%			10.60%
Regulatory equity ratio					54.00%			54.00%		52.00%
Number of intervenors | intervenor					2
Requested increase in rate amounts					$ 180
Atlanta Gas Light
Loss Contingencies [Line Items]
Public utilities, approved return on equity percentage				10.75%
Regulatory equity ratio				55.00%
Requested increase in rate amounts				$ 96
Requested increase in rate amounts, amended									$ 93
Virginia Natural Gas
Loss Contingencies [Line Items]
Approved increase (decrease) in fuel rates amount							$ (14)
Bill credits						$ 14
Virginia Natural Gas | SAVE
Loss Contingencies [Line Items]
Approved investment amount			$ 365
Infrastructure replacement program, approved investment variance amount			$ 5
Infrastructure replacement program, approved investment term			6 years
Virginia Natural Gas | SAVE | 2018
Loss Contingencies [Line Items]
Approved investment amount			$ 35
Virginia Natural Gas | SAVE | 2019
Loss Contingencies [Line Items]
Approved investment amount			40
Virginia Natural Gas | SAVE | 2020
Loss Contingencies [Line Items]
Approved investment amount			50
Virginia Natural Gas | SAVE | 2021
Loss Contingencies [Line Items]
Approved investment amount			60
Virginia Natural Gas | SAVE | 2022
Loss Contingencies [Line Items]
Approved investment amount			70
Virginia Natural Gas | SAVE | 2023
Loss Contingencies [Line Items]
Approved investment amount			70
Infrastructure replacement program, approved investment variance amount			10
Virginia Natural Gas | SAVE | 2024
Loss Contingencies [Line Items]
Approved investment amount			70
Infrastructure replacement program, approved investment variance amount			$ 10
Minimum | Atlanta Gas Light
Loss Contingencies [Line Items]
Public utilities, approved return on equity percentage				10.55%
Maximum | Atlanta Gas Light
Loss Contingencies [Line Items]
Public utilities, approved return on equity percentage				10.95%
Subsequent Event | Nicor Gas
Loss Contingencies [Line Items]
Approved increase (decrease) in fuel rates amount	$ 168
Public utilities, approved rate increase, recovery of investment, amount	$ 65
Public utilities, approved return on equity percentage	9.73%
Regulatory equity ratio	54.20%
Rehearing request period		30 days

Regulatory Matters - FERC Matte

Regulatory Matters - FERC Matters (Details) - Open Access Transmission Tariff - SCS	May 10, 2018
Loss Contingencies [Line Items]
Public utilities, approved return on equity percentage	10.60%
Moratorium period	5 years

Contingencies - General Litigat

Contingencies - General Litigation Matters (Details) $ in Millions	Sep. 27, 2019USD ($)	Mar. 14, 2019plaintiff	Nov. 30, 2018USD ($)defendantplaintiff	May 31, 2018USD ($)agreement	Apr. 30, 2018	Jun. 30, 2019USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2017claim
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff			10
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	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
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
SOUTHERN POWER CO
Loss Contingencies [Line Items]
Withholding of construction contract payments							$ 26
Gain on funds received in excess of initial replacement costs, after tax						$ 12
SOUTHERN POWER CO | RE Roserock, LLC | RE Roserock, LLC
Loss Contingencies [Line Items]
Ownership percentage by parent							51.00%

Contingencies - Environmental R

Contingencies - Environmental Remediation (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
GEORGIA POWER CO
Loss Contingencies [Line Items]
Environmental remediation liability, current and former sites	$ 16	$ 23
SOUTHERN Co GAS
Loss Contingencies [Line Items]
Environmental remediation liability, current and former sites	278	$ 294
SOUTHERN Co GAS | Location One
Loss Contingencies [Line Items]
Environmental remediation liability, current and former sites	$ 2

Contingencies - Other Matters (

Contingencies - Other Matters (Details)	Oct. 16, 2019USD ($)	Sep. 30, 2019USD ($)Facility	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)Facility	Sep. 30, 2018USD ($)	Jan. 15, 2024USD ($)	May 17, 2019USD ($)
Loss Contingencies [Line Items]
Impairment charges		$ 110,000,000	$ 36,000,000	$ 142,000,000	$ 197,000,000
ALABAMA POWER CO | Damage from Unpermitted Discharge of Fluids and/or Pollutants | Plant Gadsden
Loss Contingencies [Line Items]
Possible environmental penalty							$ 250,000
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%
MISSISSIPPI POWER CO | Scenario, Forecast | Plant Daniel Units 1 And 2
Loss Contingencies [Line Items]
Payments to acquire business						$ 1
Option to purchase, period						120 days
SOUTHERN Co GAS
Loss Contingencies [Line Items]
Impairment charges		92,000,000	$ 0	92,000,000	$ 42,000,000
SOUTHERN Co GAS | Natural Gas Storage Facility
Loss Contingencies [Line Items]
Impairment charges				92,000,000
Impairment charge, net of tax				65,000,000
Combined net book value		$ 328,000,000		$ 328,000,000
SOUTHERN Co GAS | Natural Gas Storage Facility | California
Loss Contingencies [Line Items]
Number of facilities | Facility		2		2
Subsequent Event | ALABAMA POWER CO
Loss Contingencies [Line Items]
Civil penalties	$ 50,000
Fish restocking costs	$ 172,000

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Disaggregate Revenue Sources (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 5,995	$ 6,159	$ 16,505	$ 18,158
Revenue from leases	207		547
Total retail electric and gas distribution revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	4,957	5,043	13,305	14,189
Total retail electric revenues
Disaggregation of Revenue [Line Items]
Revenue from leases	8	17	24	54
Increase (decrease) in revenue from cost recovery mechanisms	(155)	(98)	(272)	4
Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	2,056	2,148	4,832	5,266
Commercial
Disaggregation of Revenue [Line Items]
Total operating revenues	1,508	1,527	3,859	4,084
Industrial
Disaggregation of Revenue [Line Items]
Total operating revenues	916	901	2,356	2,471
Other
Disaggregation of Revenue [Line Items]
Total operating revenues	32	29	89	92
Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	445	433	2,169	2,299
Revenues not accounted for under ASC 606	3	3	11	11
Alternative revenue programs
Disaggregation of Revenue [Line Items]
Total operating revenues	0	5	0	(23)
Wholesale energy revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	477	521	1,254	1,458
Revenue from leases	141	130	324	318
Revenue from transactions accounted for as derivatives	28	63	109	217
Wholesale capacity revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	148	177	413	479
Revenue from leases	15	31	62	92
Other natural gas revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	53	54	492	530
Revenue from leases	8		24
Revenues not accounted for under ASC 606	10		37
Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	360	364	1,041	1,502
Revenue from leases	33	35	104	106
Revenues not accounted for under ASC 606	93	92	278	274
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Total operating revenues	1,841	1,740	4,762	4,716
Revenue from leases	6		19
ALABAMA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	1,694	1,584	4,286	4,208
Increase (decrease) in revenue from cost recovery mechanisms	(64)	(12)	(132)	113
ALABAMA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	796	721	1,923	1,848
ALABAMA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Total operating revenues	493	464	1,266	1,238
ALABAMA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Total operating revenues	398	392	1,077	1,103
ALABAMA POWER CO | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	7	7	20	19
ALABAMA POWER CO | Wholesale energy revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	48	62	183	234
Revenue from transactions accounted for as derivatives	3	6	8	14
ALABAMA POWER CO | Wholesale capacity revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	25	26	77	75
ALABAMA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	74	68	216	199
Revenues not accounted for under ASC 606	36	27	95	79
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Total operating revenues	2,755	2,593	6,706	6,601
Revenue from leases	18		57
GEORGIA POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	2,567	2,425	6,181	6,112
Revenue from leases	8	17	24	54
Increase (decrease) in revenue from cost recovery mechanisms	(83)	(47)	(135)	(35)
GEORGIA POWER CO | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	1,174	1,142	2,693	2,671
GEORGIA POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Total operating revenues	932	877	2,372	2,343
GEORGIA POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Total operating revenues	439	385	1,055	1,036
GEORGIA POWER CO | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	22	21	61	62
GEORGIA POWER CO | Wholesale energy revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	25	33	66	99
Revenue from transactions accounted for as derivatives	4	8	12	21
GEORGIA POWER CO | Wholesale capacity revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	14	14	41	41
GEORGIA POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	149	121	418	349
Revenue from leases	10	34	33	100
Revenues not accounted for under ASC 606	26	28	88	80
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Total operating revenues	370	358	970	956
Revenue from leases	2		7
MISSISSIPPI POWER CO | Total retail electric revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	251	254	669	660
Increase (decrease) in revenue from cost recovery mechanisms	(8)	(3)	(5)	(11)
MISSISSIPPI POWER CO | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	86	85	216	209
MISSISSIPPI POWER CO | Commercial
Disaggregation of Revenue [Line Items]
Total operating revenues	83	82	221	212
MISSISSIPPI POWER CO | Industrial
Disaggregation of Revenue [Line Items]
Total operating revenues	79	86	224	233
MISSISSIPPI POWER CO | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	3	1	8	6
MISSISSIPPI POWER CO | Wholesale energy revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	114	97	285	272
Revenue from transactions accounted for as derivatives	1	1	2	3
MISSISSIPPI POWER CO | Wholesale capacity revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	1	1	2	6
MISSISSIPPI POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	4	6	14	18
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Total operating revenues	574	635	1,527	1,699
Revenue from leases	182		460
SOUTHERN POWER CO | Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	3	5	10	10
SOUTHERN POWER CO | PPA capacity revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	131	168	384	450
Revenue from leases	31	47	111	141
SOUTHERN POWER CO | PPA energy revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	339	336	857	892
Revenue from leases	151	139	349	342
SOUTHERN POWER CO | Non-PPA revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	101	126	276	347
Revenue from transactions accounted for as derivatives	20	47	87	176
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Total operating revenues	498	492	2,661	2,861
Revenue from leases	9		26
SOUTHERN Co GAS | Wholesale Gas Services | Third Party Gross Revenues
Disaggregation of Revenue [Line Items]
Revenue from transactions accounted for as derivatives	700	900	2,700	2,700
SOUTHERN Co GAS | Natural gas distribution revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	445	438	2,169	2,276
Revenues not accounted for under ASC 606	3	3	11	11
SOUTHERN Co GAS | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	162	149	992	1,082
SOUTHERN Co GAS | Commercial
Disaggregation of Revenue [Line Items]
Total operating revenues	42	45	277	313
SOUTHERN Co GAS | Transportation
Disaggregation of Revenue [Line Items]
Total operating revenues	204	203	673	708
SOUTHERN Co GAS | Industrial
Disaggregation of Revenue [Line Items]
Total operating revenues	3	4	25	28
SOUTHERN Co GAS | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	34	32	202	168
SOUTHERN Co GAS | Alternative revenue programs
Disaggregation of Revenue [Line Items]
Total operating revenues	0	5	0	(23)
SOUTHERN Co GAS | Other natural gas revenues | Wholesale Gas Services | Third Party Gross Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	1,100	1,600	4,300	4,800
SOUTHERN Co GAS | Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	10	12	32	37
SOUTHERN Co GAS | Wholesale Gas Services
Disaggregation of Revenue [Line Items]
Total operating revenues	(4)	(10)	110	121
SOUTHERN Co GAS | Gas pipeline investments
Disaggregation of Revenue [Line Items]
Total operating revenues	8	8	24	24
Revenue from leases	8		24
SOUTHERN Co GAS | Gas marketing services
Disaggregation of Revenue [Line Items]
Total operating revenues	39	$ 44	326	403
Revenues not accounted for under ASC 606	$ 2		$ 13	$ 4

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Receivables	$ 2,523	$ 2,630
Contract Assets	132	102
Contract Liabilities	58	32
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	713	520
Contract Assets	2	0
Contract Liabilities	12	12
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Receivables	993	721
Contract Assets	91	58
Contract Liabilities	15	7
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Receivables	94	100
Contract Assets	0	0
Contract Liabilities	6	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Receivables	132	118
Contract Assets	0	0
Contract Liabilities	3	11
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Receivables	441	952
Contract Assets	0	0
Contract Liabilities	$ 1	$ 2

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Contract assets	$ 132	$ 132	$ 102
Contract liabilities	58	58	32
Revenue from contracts with customers recognized	4	29
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract assets	31	31	39
Contract liabilities	23	23	11
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract assets	2	2	0
Contract liabilities	12	12	12
Revenue from contracts with customers recognized	0	0
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract assets	91	91	58
Contract liabilities	15	15	7
Revenue from contracts with customers recognized	0	0
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract assets	0	0	0
Contract liabilities	1	1	2
Revenue from contracts with customers recognized	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract assets	0	0	0
Contract liabilities	6	6	$ 0
Revenue, remaining performance obligation	$ 0	$ 0

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers recognized	$ 4	$ 29
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers recognized	$ 0	$ 11

Revenue from Contracts with C_7

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Sep. 30, 2019USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 138
Performance obligation, expected timing of satisfaction	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 419
Performance obligation, expected timing of satisfaction	1 year
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	$ 345
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	$ 326
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	$ 317
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	$ 2,256
Performance obligation, expected timing of satisfaction
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 6
Performance obligation, expected timing of satisfaction	3 months
ALABAMA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 23
Performance obligation, expected timing of satisfaction	1 year
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	$ 27
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	$ 23
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	$ 22
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	$ 140
Performance obligation, expected timing of satisfaction
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 15
Performance obligation, expected timing of satisfaction	3 months
GEORGIA POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 56
Performance obligation, expected timing of satisfaction	1 year
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	$ 47
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	$ 31
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	$ 32
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	$ 83
Performance obligation, expected timing of satisfaction
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 61
Performance obligation, expected timing of satisfaction	3 months
SOUTHERN POWER CO | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 309
Performance obligation, expected timing of satisfaction	1 year
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	$ 291
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	$ 290
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	$ 283
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	$ 2,180
Performance obligation, expected timing of satisfaction

Consolidated Entities and Equ_3

Consolidated Entities and Equity Method Investments - Narrative (Details) $ in Millions	May 29, 2019USD ($)	Sep. 30, 2019USD ($)investor	Oct. 04, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2014miBcf
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%
SP Solar Holdings I, LP | Variable Interest Entity, Primary Beneficiary | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets		$ 6,500
Liabilities		383
Noncontrolling interests related to other partners' interests		$ 1,200
SP Wind | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage		60.00%
Number of financial investors | investor		3
SP Wind | Financial Investors
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage		40.00%
SP Wind | Variable Interest Entity, Primary Beneficiary | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets		$ 2,500
Liabilities		132
Noncontrolling interests related to other partners' interests		46
Triton | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Pre tax loss on disposition of investment	$ 6
After-tax gain on disposition of investment	7
Income tax benefit on disposition of investment	$ 13
Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Ownership percentage, equity method investment					5.00%
Pipeline infrastructure | mi					605
PennEast Pipeline | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Ownership percentage, equity method investment					20.00%
Pipeline infrastructure | mi					118
Minimum | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate				$ 7,000
Minimum | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Natural gas pipeline capacity (volume) | Bcf					1.5
Construction contingency estimate				350
Minimum | PennEast Pipeline | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Natural gas pipeline capacity (volume) | Bcf					1
Maximum | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate				7,800
Maximum | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate				$ 390
Subsequent Event | Minimum | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate			$ 7,300
Subsequent Event | Minimum | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate			365
Subsequent Event | Maximum | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate			7,800
Subsequent Event | Maximum | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Construction contingency estimate			$ 390
Revolving Credit Facility | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Borrowing capacity		3,400
Financial Guarantee | Atlantic Coast Pipeline(b) | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Guarantor obligations		$ 85

Consolidated Entities and Equ_4

Consolidated Entities and Equity Method Investments - Balance Sheet Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,540	$ 1,580
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,487	1,538
SOUTHERN Co GAS | SNG(a)
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,210	1,261
SOUTHERN Co GAS | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Investment Balance	109	83
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Investment Balance	80	71
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 88	$ 123

Consolidated Entities and Equ_5

Consolidated Entities and Equity Method Investments - Income Statement Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 39	$ 36	$ 120	$ 108
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	35	34	115	108
SOUTHERN Co GAS | SNG(a)
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	30	29	104	95
SOUTHERN Co GAS | Atlantic Coast Pipeline(b)
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	3	1	9	4
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	2	2	5	4
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Earnings from Equity Method Investments	$ 0	$ 2	$ (3)	$ 5

Consolidated Entities and Equ_6

Consolidated Entities and Equity Method Investments - Investment in SNG (Details) - SNG(a) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement Information
Revenues	$ 152	$ 145	$ 473	$ 451
Operating income	82	71	274	230
Net income	$ 60	$ 58	$ 208	$ 190

Financing - Narrative (Details)

Financing - Narrative (Details)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Jun. 30, 2019USD ($)loan

May 31, 2019USD ($)

Mar. 31, 2019USD ($)loan

Jan. 31, 2019USD ($)

Sep. 30, 2019USD ($)shares

Sep. 30, 2018shares

Sep. 30, 2019USD ($)shares

Sep. 30, 2018USD ($)shares

Dec. 31, 2014

Oct. 30, 2019USD ($)

Sep. 29, 2019USD ($)

Aug. 31, 2019USD ($)

Apr. 30, 2019USD ($)

Aug. 31, 2018

Debt Instrument [Line Items]

Variable rate pollution control revenue bonds outstanding

$ 1,400,000,000

$ 1,400,000,000

Borrowing capacity

$ 7,608,000,000

7,608,000,000

Repayments of short-term debt

$ 1,850,000,000

$ 1,800,000,000

Stock-based compensation awards not included in the diluted earnings per share calculation because they were anti-dilutive (in shares) | shares

0

0

0

0

Senior Notes

Debt Instrument [Line Items]

Repayments of debt

$ 1,200,000,000

Senior Notes | 1.85% Notes

Debt Instrument [Line Items]

Interest rate

1.85%

Repurchase amount

$ 522,000,000

Debt face amount

$ 1,000,000,000

Senior Notes | Series 2014B Notes

Debt Instrument [Line Items]

Interest rate

2.15%

Repurchase amount

$ 180,000,000

Debt face amount

350,000,000

Senior Notes | Series 2018A Notes

Debt Instrument [Line Items]

Repurchase amount

504,000,000

Debt face amount

750,000,000

Senior Notes | Series 2017A Notes

Debt Instrument [Line Items]

Redeemed aggregate principal amount

$ 300,000,000

$ 300,000,000

Junior Subordinated Debt | Series 2019A Remarketable Junior Subordinated Notes

Debt Instrument [Line Items]

Debt face amount

$ 1,725,000,000

Notes Payable to Banks | Uncommitted Bank Credit Arrangement

Debt Instrument [Line Items]

Repayments of short-term debt

250,000,000

Notes Payable to Banks | Floating Rate Bank Term Loan Agreement

Debt Instrument [Line Items]

Repayments of short-term debt

1,500,000,000

ALABAMA POWER CO

Debt Instrument [Line Items]

Variable rate pollution control revenue bonds outstanding

854,000,000

854,000,000

Fixed rate pollution control revenue bonds outstanding

87,000,000

87,000,000

Borrowing capacity

1,328,000,000

1,328,000,000

ALABAMA POWER CO | Multi-year Credit Arrangement

Debt Instrument [Line Items]

Borrowing capacity

$ 525,000,000

$ 525,000,000

$ 500,000,000

ALABAMA POWER CO | Senior Notes | Series 2019A 3.45% Notes

Debt Instrument [Line Items]

Interest rate

3.45%

3.45%

Debt face amount

$ 600,000,000

$ 600,000,000

GEORGIA POWER CO

Debt Instrument [Line Items]

Variable rate pollution control revenue bonds outstanding

550,000,000

550,000,000

Borrowing capacity

$ 1,750,000,000

1,750,000,000

Repayments of short-term debt

$ 0

$ 150,000,000

GEORGIA POWER CO | Senior Notes | Series 2019A 2.20% Notes

Debt Instrument [Line Items]

Interest rate

2.20%

2.20%

Debt face amount

$ 400,000,000

$ 400,000,000

GEORGIA POWER CO | Senior Notes | Series 2019B

Debt Instrument [Line Items]

Interest rate

2.65%

2.65%

Debt face amount

$ 350,000,000

$ 350,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project) First Series 1992

Debt Instrument [Line Items]

Redeemed aggregate principal amount

13,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Eighth Series 1994

Debt Instrument [Line Items]

Redeemed aggregate principal amount

20,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1995

Debt Instrument [Line Items]

Redeemed aggregate principal amount

$ 75,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009

Debt Instrument [Line Items]

Debt face amount

$ 173,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013

Debt Instrument [Line Items]

Debt face amount

105,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008

Debt Instrument [Line Items]

Debt face amount

$ 65,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994

Debt Instrument [Line Items]

Debt face amount

$ 55,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995

Debt Instrument [Line Items]

Debt face amount

30,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994

Debt Instrument [Line Items]

Debt face amount

20,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994

Debt Instrument [Line Items]

Debt face amount

10,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1994

Debt Instrument [Line Items]

Debt face amount

$ 55,000,000

GEORGIA POWER CO | Municipal bonds | Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2013

Debt Instrument [Line Items]

Debt face amount

72,000,000

GEORGIA POWER CO | Plant Vogtle Units 3 And 4

Debt Instrument [Line Items]

Undivided ownership interest

45.70%

GEORGIA POWER CO | Notes Payable to Banks

Debt Instrument [Line Items]

Number of short-term loans | loan

2

GEORGIA POWER CO | Notes Payable to Banks | First Short-Term Floating Rate Bank Loan

Debt Instrument [Line Items]

Debt face amount

$ 125,000,000

GEORGIA POWER CO | Notes Payable to Banks | Second Short-Term Floating Rate Bank Loan

Debt Instrument [Line Items]

Debt face amount

125,000,000

125,000,000

GEORGIA POWER CO | Term Loan

Debt Instrument [Line Items]

Number of term loan facilities | loan

2

GEORGIA POWER CO | 2014 FFB Credit Facility

Debt Instrument [Line Items]

Eligible project costs to be reimbursed

$ 5,130,000,000

Eligible project costs to be reimbursed, percentage (may not exceed)

70.00%

Borrowings made

$ 835,000,000

Interest rate

3.213%

Borrowings outstanding

3,460,000,000

3,460,000,000

Amortization period for line of credit facility

5 years

GEORGIA POWER CO | 2014 FFB Credit Facility | U.S. Treasury Rate

Debt Instrument [Line Items]

Basis spread

0.375%

GEORGIA POWER CO | Additional FFB Credit Facility

Debt Instrument [Line Items]

Eligible project costs to be reimbursed, percentage (may not exceed)

70.00%

Amounts received under Guarantee Settlement Agreement, less Customer Refunds

$ 1,492,000,000

MISSISSIPPI POWER CO

Debt Instrument [Line Items]

Variable rate pollution control revenue bonds outstanding

40,000,000

40,000,000

Borrowing capacity

150,000,000

150,000,000

Repayments of short-term debt

0

300,000,000

MISSISSIPPI POWER CO | Municipal bonds | Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002

Debt Instrument [Line Items]

Debt face amount

$ 43,000,000

MISSISSIPPI POWER CO | Credit Arrangement

Debt Instrument [Line Items]

Borrowing capacity

50,000,000

50,000,000

SOUTHERN Co GAS

Debt Instrument [Line Items]

Borrowing capacity

1,750,000,000

1,750,000,000

SOUTHERN POWER CO

Debt Instrument [Line Items]

Borrowing capacity

$ 600,000,000

600,000,000

600,000,000

750,000,000

Repayments of short-term debt

100,000,000

$ 0

SOUTHERN POWER CO | Notes Payable to Banks

Debt Instrument [Line Items]

Repayments of short-term debt

100,000,000

Southern Company Gas Capital

Debt Instrument [Line Items]

Borrowing capacity

$ 1,750,000,000

1,250,000,000

1,250,000,000

$ 1,900,000,000

Nicor Gas

Debt Instrument [Line Items]

Borrowing capacity

$ 500,000,000

$ 500,000,000

Nicor Gas | First Mortgage Bonds

Debt Instrument [Line Items]

Debt face amount

$ 200,000,000

Plant Vogtle Units 3 And 4 | GEORGIA POWER CO

Debt Instrument [Line Items]

Undivided ownership interest

45.70%

45.70%

Failure to vote, percentage of ownership interests

90.00%

90.00%

Scenario, Forecast | Nicor Gas | First Mortgage Bonds

Debt Instrument [Line Items]

Debt face amount

$ 100,000,000

Financing - Schedule of Credit

Financing - Schedule of Credit Arrangements (Details) - USD ($)	Sep. 30, 2019	Sep. 29, 2019	May 31, 2019	Apr. 30, 2019
Line of Credit Facility [Line Items]
Expires, 2020	$ 33,000,000
Expires, 2022	675,000,000
Expires, 2024	6,900,000,000
Total	7,608,000,000
Unused	7,576,000,000
Due within One Year	33,000,000
Southern Company
Line of Credit Facility [Line Items]
Expires, 2020	0
Expires, 2022	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, 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, 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, 2024	0
Total	150,000,000
Unused	150,000,000
Due within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
Expires, 2020	0
Expires, 2022	0
Expires, 2024	600,000,000
Total	600,000,000		$ 600,000,000	$ 750,000,000
Unused	591,000,000
Due within One Year	0
SOUTHERN POWER CO | Standby Letters of Credit
Line of Credit Facility [Line Items]
Total	120,000,000
Unused	30,000,000
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
Expires, 2020	0
Expires, 2022	0
Expires, 2024	1,750,000,000
Total	1,750,000,000
Unused	1,745,000,000
Due within One Year	0
Other
Line of Credit Facility [Line Items]
Expires, 2020	30,000,000
Expires, 2022	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		$ 1,750,000,000	$ 1,900,000,000
Nicor Gas
Line of Credit Facility [Line Items]
Total	500,000,000
Multi-year Credit Arrangement | ALABAMA POWER CO
Line of Credit Facility [Line Items]
Total	$ 525,000,000	$ 500,000,000

Financing - Schedule of Long-Te

Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 1,350
Senior Note Maturities, Redemptions, and Repurchases	2,900
Revenue Bond Issuances and Reofferings of Purchased Bonds	627
Revenue Bond Maturities, Redemptions, and Repurchases	248
Other Long-Term Debt Issuances	2,760
Other Long-Term Debt Redemptions and Maturities	69
Parent Company | Southern Company
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities, Redemptions, and Repurchases	2,400
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	1,725
Other Long-Term Debt Redemptions and Maturities	0
Subsidiaries | ALABAMA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	600
Senior Note Maturities, Redemptions, and Repurchases	200
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	1
Subsidiaries | GEORGIA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	750
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	584
Revenue Bond Maturities, Redemptions, and Repurchases	223
Other Long-Term Debt Issuances	835
Other Long-Term Debt Redemptions and Maturities	11
Subsidiaries | MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	43
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
Subsidiaries | SOUTHERN Co GAS
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities, Redemptions, and Repurchases	300
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	200
Other Long-Term Debt Redemptions and Maturities	50
Subsidiaries | Other
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	25
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	14
Eliminations | Subsidiaries
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities, Redemptions, and Repurchases	0
Revenue Bond Issuances and Reofferings of Purchased Bonds	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	$ (7)

Financing - Equity Units (Detai

Financing - Equity Units (Details) - USD ($)	1 Months Ended
	Aug. 31, 2019	Sep. 30, 2019
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Number of shares indexed (in shares)	34,500,000
Equity units, per unit issuance price (in dollars per share)	$ 50
Proceeds from issuance of mandatory redeemable capital securities	$ 1,682,000,000
Maximum number of shares (in shares)	30,200,000
Junior Subordinated Debt
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Contract adjustment payments, accretion period	3 years
Series 2019A Remarketable Junior Subordinated Notes | Junior Subordinated Debt
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Debt face amount	$ 1,725,000,000
Equity units, percentage interest in attached debt instrument	0.0025%
Series 2019B Remarketable Junior Subordinated Notes | Junior Subordinated Debt
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, percentage interest in attached debt instrument	0.0025%
Series 2019A And Series 2019B Remarketable Junior Subordinated Notes | Junior Subordinated Debt
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Distribution rate, percentage	6.75%
Interest rate	2.70%
Contract adjustment rate, percentage	4.05%
Purchase contract adjustment liability		$ 198,000,000
Purchase contract adjustment liability, current		$ 63,000,000
Anti-Dilution Scenario One
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, coversion ratio (in shares)	0.7284
Anti-Dilution Scenario One | Minimum
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, stock price upper threshold (in dollars per share)	$ 68.64
Anti-Dilution Scenario Two
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, per unit issuance price (in dollars per share)	50
Anti-Dilution Scenario Two | Minimum
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, stock price lower threshold (in dollars per share)	57.20
Anti-Dilution Scenario Two | Maximum
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, stock price upper threshold (in dollars per share)	$ 68.64
Anti-Dilution Scenario Three
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, coversion ratio (in shares)	0.8741
Anti-Dilution Scenario Three | Maximum
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Equity units, stock price lower threshold (in dollars per share)	$ 57.20

Financing - Shares Used to Comp

Financing - Shares Used to Compute Diluted Earnings Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Disclosure [Abstract]
Stock-based compensation awards not included in the diluted earnings per share calculation because they were anti-dilutive (in shares)	0	0	0	0
As reported shares	1,048,000,000	1,023,000,000	1,043,000,000	1,016,000,000
Effect of stock-based compensation	9,000,000	6,000,000	8,000,000	5,000,000
Diluted shares	1,057,000,000	1,029,000,000	1,051,000,000	1,021,000,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Billions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	30.20%	22.70%
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	22.60%	25.50%
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	16.30%	20.80%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	(13.60%)	(220.30%)
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	15.00%	61.80%
Investment Tax Credit Carryforward
Income Tax Contingency [Line Items]
Federal ITC/PTC carryforward	$ 1.8		$ 2.4

Retirement Benefits (Details)

Retirement Benefits (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Amortization:
Net (gain)/loss
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year	$ 0		$ 0
Pension Plans and Postretirement Plans
Service cost	73,000,000	90,000,000	219,000,000	$ 269,000,000
Interest cost	123,000,000	116,000,000	369,000,000	348,000,000
Expected return on plan assets	(222,000,000)	(236,000,000)	(664,000,000)	(707,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	2,000,000	3,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	30,000,000	53,000,000	90,000,000	160,000,000
Net periodic pension cost (income)	5,000,000	24,000,000	16,000,000	73,000,000
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	17,000,000	19,000,000	51,000,000	58,000,000
Interest cost	28,000,000	26,000,000	85,000,000	76,000,000
Expected return on plan assets	(51,000,000)	(51,000,000)	(154,000,000)	(155,000,000)
Amortization:
Prior service costs	0	0	1,000,000	1,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	9,000,000	13,000,000	27,000,000	40,000,000
Net periodic pension cost (income)	3,000,000	7,000,000	10,000,000	20,000,000
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	19,000,000	22,000,000	56,000,000	65,000,000
Interest cost	38,000,000	34,000,000	116,000,000	104,000,000
Expected return on plan assets	(73,000,000)	(74,000,000)	(219,000,000)	(222,000,000)
Amortization:
Prior service costs	0	1,000,000	1,000,000	2,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	11,000,000	18,000,000	33,000,000	52,000,000
Net periodic pension cost (income)	(5,000,000)	1,000,000	(13,000,000)	1,000,000
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	5,000,000	9,000,000	13,000,000
Interest cost	6,000,000	5,000,000	17,000,000	15,000,000
Expected return on plan assets	(10,000,000)	(11,000,000)	(30,000,000)	(31,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	1,000,000	3,000,000	4,000,000	8,000,000
Net periodic pension cost (income)	0	2,000,000	0	5,000,000
Pension Plans | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	3,000,000	5,000,000	7,000,000
Interest cost	1,000,000	1,000,000	4,000,000	4,000,000
Expected return on plan assets	(2,000,000)	(3,000,000)	(7,000,000)	(8,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	1,000,000
Net periodic pension cost (income)	1,000,000	1,000,000	2,000,000	4,000,000
Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	7,000,000	8,000,000	19,000,000	24,000,000
Interest cost	9,000,000	10,000,000	27,000,000	29,000,000
Expected return on plan assets	(15,000,000)	(18,000,000)	(45,000,000)	(53,000,000)
Amortization:
Prior service costs	(1,000,000)	(1,000,000)	(2,000,000)	(2,000,000)
Regulatory asset	3,000,000	4,000,000	10,000,000	11,000,000
Net (gain)/loss	1,000,000	3,000,000	2,000,000	9,000,000
Net periodic pension cost (income)	4,000,000	6,000,000	11,000,000	18,000,000
Postretirement Benefits
Pension Plans and Postretirement Plans
Service cost	5,000,000	6,000,000	14,000,000	18,000,000
Interest cost	18,000,000	19,000,000	52,000,000	56,000,000
Expected return on plan assets	(16,000,000)	(17,000,000)	(49,000,000)	(51,000,000)
Amortization:
Prior service costs	0	2,000,000	2,000,000	5,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	(1,000,000)	3,000,000	(2,000,000)	10,000,000
Net periodic pension cost (income)	6,000,000	13,000,000	17,000,000	38,000,000
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	3,000,000	4,000,000
Interest cost	4,000,000	5,000,000	12,000,000	13,000,000
Expected return on plan assets	(6,000,000)	(7,000,000)	(19,000,000)	(20,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	3,000,000	3,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	1,000,000
Net periodic pension cost (income)	0	0	(1,000,000)	1,000,000
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	4,000,000	5,000,000
Interest cost	6,000,000	7,000,000	19,000,000	21,000,000
Expected return on plan assets	(7,000,000)	(6,000,000)	(19,000,000)	(19,000,000)
Amortization:
Prior service costs	0	0	0	1,000,000
Regulatory asset	0	0	0	0
Net (gain)/loss	1,000,000	2,000,000	1,000,000	6,000,000
Net periodic pension cost (income)	2,000,000	5,000,000	5,000,000	14,000,000
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	0	1,000,000	1,000,000
Interest cost	0	0	2,000,000	2,000,000
Expected return on plan assets	0	0	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	1,000,000	0	2,000,000	2,000,000
Postretirement Benefits | SOUTHERN POWER CO
Pension Plans and Postretirement Plans
Service cost	0	1,000,000	0	1,000,000
Interest cost	0	0	0	0
Expected return on plan assets	0	0	0	0
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	0	1,000,000	0	1,000,000
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0	0	1,000,000	1,000,000
Interest cost	2,000,000	2,000,000	7,000,000	7,000,000
Expected return on plan assets	(1,000,000)	(1,000,000)	(4,000,000)	(5,000,000)
Amortization:
Prior service costs	0	0	0	0
Regulatory asset	1,000,000	2,000,000	4,000,000	5,000,000
Net (gain)/loss	0	0	(2,000,000)	0
Net periodic pension cost (income)	$ 2,000,000	$ 3,000,000	$ 6,000,000	$ 8,000,000

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets:
Derivatives	$ 141	$ 313
Liabilities:
Derivatives	257	235
Collateral already posted, aggregate fair value	166
ALABAMA POWER CO
Assets:
Derivatives	3	2
Liabilities:
Derivatives	20	6
GEORGIA POWER CO
Assets:
Derivatives	0	0
Investments in trusts	50
Liabilities:
Derivatives	106	17
MISSISSIPPI POWER CO
Assets:
Derivatives	0	1
Liabilities:
Derivatives	22	7
SOUTHERN POWER CO
Assets:
Derivatives	0	76
Liabilities:
Derivatives	36	28
SOUTHERN Co GAS
Assets:
Derivatives	136	233
Liabilities:
Derivatives	66	124
Total
Collateral already posted, aggregate fair value	166	$ 277
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	2,085
Other investments	24
Total	4,594
Liabilities:
Contingent consideration	21
Total	792
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	2,078
Other investments	9
Total	3,200
Liabilities:
Contingent consideration	0
Total	412
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	7
Other investments	15
Total	1,307
Liabilities:
Contingent consideration	0
Total	331
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Other investments	0
Total	34
Liabilities:
Contingent consideration	21
Total	49
Fair Value, Measurements, Recurring | Net Asset Value as a Practical Expedient (NAV)
Assets:
Total	53
Fair Value, Measurements, Recurring | Energy-related derivatives
Assets:
Derivatives	487
Liabilities:
Derivatives	667
Fair Value, Measurements, Recurring | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	297
Liabilities:
Derivatives	412
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	156
Liabilities:
Derivatives	227
Fair Value, Measurements, Recurring | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	34
Liabilities:
Derivatives	28
Fair Value, Measurements, Recurring | Interest rate derivatives
Assets:
Derivatives	2
Liabilities:
Derivatives	72
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	2
Liabilities:
Derivatives	72
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	32
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	32
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	839
Fair Value, Measurements, Recurring | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	713
Fair Value, Measurements, Recurring | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	126
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	265
Fair Value, Measurements, Recurring | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	61
Fair Value, Measurements, Recurring | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	204
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	301
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	301
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	86
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	86
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	330
Fair Value, Measurements, Recurring | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	24
Fair Value, Measurements, Recurring | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	306
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	82
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	82
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	53
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	53
Fair Value, Measurements, Recurring | Cash and cash equivalents
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	1
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | Other
Assets:
Investments in trusts	23
Fair Value, Measurements, Recurring | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	17
Fair Value, Measurements, Recurring | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | Other | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | ALABAMA POWER CO
Assets:
Cash equivalents	1,143
Other investments	15
Total	2,136
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	1,136
Other investments
Total	1,690
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	7
Other investments	15
Total	393
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	53
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Energy-related derivatives
Assets:
Derivatives	5
Liabilities:
Derivatives	22
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	22
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	578
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	464
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Domestic equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	114
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	121
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	61
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Foreign equity | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	60
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	23
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	23
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	166
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	24
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	142
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	26
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	26
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	53
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	53
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other
Assets:
Investments in trusts	5
Fair Value, Measurements, Recurring | ALABAMA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	5
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	392
Total	1,384
Liabilities:
Total	109
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	392
Total	652
Liabilities:
Total	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	732
Liabilities:
Total	109
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	0
Liabilities:
Total	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Energy-related derivatives
Assets:
Derivatives	3
Liabilities:
Derivatives	49
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	3
Liabilities:
Derivatives	49
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 | Interest rate derivatives
Liabilities:
Derivatives	60
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Interest rate derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Interest rate derivatives | Significant Other Observable Inputs (Level 2)
Liabilities:
Derivatives	60
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Interest rate derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity
Assets:
Investments in trusts	249
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Domestic equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	248
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	140
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	140
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	277
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	277
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	86
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	86
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	164
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	164
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	55
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	55
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	18
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Investments in trusts	12
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Significant Other Observable Inputs (Level 2)
Assets:
Investments in trusts	6
Fair Value, Measurements, Recurring | GEORGIA POWER CO | Other | Significant Unobservable Inputs (Level 3)
Assets:
Investments in trusts	0
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO
Assets:
Cash equivalents	234
Total	236
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	234
Total	234
Fair Value, Measurements, Recurring | MISSISSIPPI POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	2
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	2
Liabilities:
Derivatives	24
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	2
Liabilities:
Derivatives	24
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	23
Liabilities:
Contingent consideration	21
Total	57
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	23
Liabilities:
Contingent consideration	0
Total	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Liabilities:
Contingent consideration	0
Total	36
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Liabilities:
Contingent consideration	21
Total	21
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives
Liabilities:
Derivatives	4
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Liabilities:
Derivatives	4
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivatives	0
Fair Value, Measurements, Recurring | SOUTHERN POWER CO | Foreign currency derivatives
Liabilities:
Derivatives	32
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	32
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:
Total	509
Liabilities:
Total	573
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total	298
Liabilities:
Total	412
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Other Observable Inputs (Level 2)
Assets:
Total	177
Liabilities:
Total	133
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Significant Unobservable Inputs (Level 3)
Assets:
Total	34
Liabilities:
Total	28
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives
Assets:
Derivatives	477
Liabilities:
Derivatives	568
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivatives	297
Liabilities:
Derivatives	412
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivatives	146
Liabilities:
Derivatives	128
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Energy-related derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivatives	34
Liabilities:
Derivatives	28
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Interest rate derivatives
Liabilities:
Derivatives	5
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	5
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	11
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	11
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	4
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	4
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, Recurring | SOUTHERN Co GAS | Cash and cash equivalents
Assets:
Non-qualified deferred compensation trusts	1
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	1
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash and cash equivalents | Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	0
Fair Value, Measurements, Recurring | SOUTHERN Co GAS | Cash and cash equivalents | Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Increase (Decrease) In Fair Value Of Funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 27	$ 58	$ 255	$ 68
ALABAMA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	15	39	140	49
GEORGIA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 12	$ 19	$ 115	$ 19

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) $ in Millions	Sep. 30, 2019USD ($)$ / MMBTU
ALABAMA POWER CO | Private equity
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair value	$ 53
Unfunded commitments	54
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	$ 5
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	(0.05)
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	0.74

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions	Sep. 30, 2019USD ($)
Long-term debt, including securities due within one year:
Carrying amount	$ 45,182
Fair value	49,424
ALABAMA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	8,516
Fair value	9,646
GEORGIA POWER CO
Long-term debt, including securities due within one year:
Carrying amount	11,787
Fair value	13,001
MISSISSIPPI POWER CO
Long-term debt, including securities due within one year:
Carrying amount	1,616
Fair value	1,717
SOUTHERN POWER CO
Long-term debt, including securities due within one year:
Carrying amount	4,960
Fair value	5,290
SOUTHERN Co GAS
Long-term debt, including securities due within one year:
Carrying amount	5,755
Fair value	$ 6,489

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component (Details) - SOUTHERN Co GAS - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (10)	$ 0
Transfers to Level 3	0	(33)
Transfers from Level 3	3	3
Instruments realized or otherwise settled during period	(2)	(2)
Changes in fair value	14	37
Ending balance	$ 5	$ 5

Derivatives - Energy-Related an

Derivatives - Energy-Related and Interest Rate Derivatives (Details) MMBTU in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)MMBTU
Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	475
Interest rate derivatives
Interest rate derivatives
Notional Amount	$ 2,950
Fair Value Gain (Loss) at September 30, 2019	$ (71)
ALABAMA POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	89
GEORGIA POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	184
GEORGIA POWER CO | Interest rate derivatives | March 2025 | Cash Flow Hedges of Forecasted Debt
Interest rate derivatives
Notional Amount	$ 250
Weighted Average Interest Rate Paid	2.23%
Fair Value Gain (Loss) at September 30, 2019	$ (9)
GEORGIA POWER CO | Interest rate derivatives | March 2030 | Cash Flow Hedges of Forecasted Debt
Interest rate derivatives
Notional Amount	$ 250
Weighted Average Interest Rate Paid	2.40%
Fair Value Gain (Loss) at September 30, 2019	$ (20)
GEORGIA POWER CO | Interest rate derivatives | February 2044 | Cash Flow Hedges of Forecasted Debt
Interest rate derivatives
Notional Amount	$ 250
Weighted Average Interest Rate Paid	2.48%
Fair Value Gain (Loss) at September 30, 2019	$ (30)
GEORGIA POWER CO | Interest rate derivatives | December 2019 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 200
Interest Rate Received	4.25%
Fair Value Gain (Loss) at September 30, 2019	$ (1)
GEORGIA POWER CO | LIBOR | Interest rate derivatives | December 2019 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	2.46%
MISSISSIPPI POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	99
SOUTHERN POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	9
SOUTHERN Co GAS | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | MMBTU	94
SOUTHERN Co GAS | Energy-related, Natural Gas | Derivatives not designated as hedging instruments | Long
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume | MMBTU	4,100
SOUTHERN Co GAS | Energy-related, Natural Gas | Derivatives not designated as hedging instruments | Short
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume | MMBTU	4,100
SOUTHERN Co GAS | Interest rate derivatives | September 2030 | Cash Flow Hedges of Forecasted Debt
Interest rate derivatives
Notional Amount	$ 200
Weighted Average Interest Rate Paid	1.81%
Fair Value Gain (Loss) at September 30, 2019	$ (5)
Southern Company | Interest rate derivatives | June 2020 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 300
Interest Rate Received	2.75%
Fair Value Gain (Loss) at September 30, 2019	$ (1)
Southern Company | Interest rate derivatives | July 2021 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 1,500
Interest Rate Received	2.35%
Fair Value Gain (Loss) at September 30, 2019	$ (5)
Southern Company | LIBOR | Interest rate derivatives | June 2020 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.92%
Southern Company | LIBOR | Interest rate derivatives | July 2021 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.87%

Derivatives - Narrative (Detail

Derivatives - Narrative (Details) MMBTU in Millions	9 Months Ended
	Sep. 30, 2019USD ($)MMBTU	Dec. 31, 2018USD ($)
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	25
Cash flow hedge gain (loss) to be reclassified within twelve months	$ (21,000,000)
Collateral already posted, aggregate fair value	$ 166,000,000
ALABAMA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	4
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 0
GEORGIA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	8
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 0
MISSISSIPPI POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	4
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 0
SOUTHERN POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	9
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 0
SOUTHERN Co GAS
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months	0
Collateral already posted, aggregate fair value	166,000,000	$ 277,000,000
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)
Registrants | Derivative Counterparties
Derivative [Line Items]
Collateral already posted, aggregate fair value	$ 0

Derivatives - Foreign Currency

Derivatives - Foreign Currency Derivatives (Details) - 9 months ended Sep. 30, 2019 - Cash Flow Hedges of Forecasted Debt - Foreign currency derivatives € in Millions, $ in Millions	USD ($)	EUR (€)
Derivative [Line Items]
Pay Notional	$ 1,241
Receive Notional | €		€ 1,100
Fair Value Gain (Loss) at September 30, 2019	(32)
SOUTHERN POWER CO | June 2022
Derivative [Line Items]
Pay Notional	$ 677
Pay Rate	2.95%
Receive Notional | €		600
Receive Rate	1.00%
Fair Value Gain (Loss) at September 30, 2019	$ (21)
SOUTHERN POWER CO | June 2026
Derivative [Line Items]
Pay Notional	$ 564
Pay Rate	3.78%
Receive Notional | €		€ 500
Receive Rate	1.85%
Fair Value Gain (Loss) at September 30, 2019	$ (11)

Derivatives - Derivative Financ

Derivatives - Derivative Financial Statement Presentation and Amounts With Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivatives, assets	$ 489	$ 837
Derivatives, liabilities	771	1,036
Derivative asset, Gross amounts offset	(348)	(524)
Derivative liability, Gross amounts offset	(514)	(801)
Derivative asset	141	313
Derivative liability	257	235
Collateral already posted, aggregate fair value	166
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	476	741
Derivatives, liabilities	553	900
Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	311	561
Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	342	575
Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	165	180
Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	211	325
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes
Derivatives, Fair Value [Line Items]
Derivatives, assets	11	17
Derivatives, liabilities	105	55
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	8
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	61	23
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	6	9
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	44	26
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Assets held for sale, current
Derivatives, Fair Value [Line Items]
Derivatives, assets		0
Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Liabilities held for sale, current
Derivatives, Fair Value [Line Items]
Derivatives, liabilities		6
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	79
Derivatives, liabilities	113	81
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	3
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	8	7
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	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 assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	72	19
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	2	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	30
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	23
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	75
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	8	0
ALABAMA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	6
Derivatives, liabilities	22	10
Derivative asset, Gross amounts offset	(2)	(4)
Derivative liability, Gross amounts offset	(2)	(4)
Derivative asset	3	2
Derivative liability	20	6
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	6
Derivatives, liabilities	22	10
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	3	3
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	12	4
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	3
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	10	6
GEORGIA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	3	6
Derivatives, liabilities	109	23
Derivative asset, Gross amounts offset	(3)	(6)
Derivative liability, Gross amounts offset	(3)	(6)
Derivative asset	0	0
Derivative liability	106	17
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	3	6
Derivatives, liabilities	49	21
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	27	8
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	4
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	22	13
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	60	2
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	60	2
MISSISSIPPI POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	3
Derivatives, liabilities	24	9
Derivative asset, Gross amounts offset	(2)	(2)
Derivative liability, Gross amounts offset	(2)	(2)
Derivative asset	0	1
Derivative liability	22	7
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	2	3
Derivatives, liabilities	24	9
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	12	3
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	2
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	12	6
SOUTHERN POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	79
Derivatives, liabilities	36	31
Derivative asset, Gross amounts offset	0	(3)
Derivative liability, Gross amounts offset	0	(3)
Derivative asset	0	76
Derivative liability	36	28
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	0	79
Derivatives, liabilities	36	31
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	3
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	6
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	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	23
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	75
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	8	0
SOUTHERN Co GAS
Derivatives, Fair Value [Line Items]
Derivatives, assets	477	741
Derivatives, liabilities	573	909
Derivative asset, Gross amounts offset	(341)	(508)
Derivative liability, Gross amounts offset	(507)	(785)
Derivative asset	136	233
Derivative liability	66	124
Collateral already posted, aggregate fair value	166	277
Weather derivative premium		8
SOUTHERN Co GAS | Gain (loss) on energy-related cash flow hedges
Derivatives, Fair Value [Line Items]
Collateral already posted, aggregate fair value	8
SOUTHERN Co GAS | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	476	739
Derivatives, liabilities	553	899
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	165	180
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	211	325
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	311	559
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Gain (loss) on energy-related cash flow hedges | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	342	574
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	2
Derivatives, liabilities	10	9
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | 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 | Gain (loss) on energy-related cash flow hedges | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	10	8
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	0	0
Derivatives, liabilities	10	1
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	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 | Gain (loss) on energy-related cash flow hedges | Assets from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Derivatives designated as hedging instruments for regulatory purposes | Gain (loss) on energy-related cash flow hedges | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	1
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	0
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	$ 5	$ 0

Derivatives - Pre-tax Effects o

Derivatives - Pre-tax Effects of Derivatives Designated as Cash Flow Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	$ 166		$ 166
Gain (Loss) Recognized in OCI on Derivative	(125)	$ (15)	(206)	$ (26)
SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(71)	(15)	(112)	(26)
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	166		166		$ 277
Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(86)		(86)		(40)
Gain (Loss) Recognized in OCI on Derivative	(5)	(5)	(11)	7
Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(55)		(55)		(19)
Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(37)		(37)		(16)
Energy-related derivatives | Assets held for sale, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					(6)
Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	6		6		1
Energy-related derivatives | ALABAMA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(16)		(16)		(6)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(11)		(11)		(3)
Energy-related derivatives | ALABAMA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(8)		(8)		(3)
Energy-related derivatives | ALABAMA POWER CO | Assets held for sale, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					0
Energy-related derivatives | ALABAMA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	3		3		0
Energy-related derivatives | GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(46)		(46)		(15)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(27)		(27)		(6)
Energy-related derivatives | GEORGIA POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(19)		(19)		(9)
Energy-related derivatives | GEORGIA POWER CO | Assets held for sale, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					0
Energy-related derivatives | GEORGIA POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		0
Energy-related derivatives | MISSISSIPPI POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(22)		(22)		(6)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(12)		(12)		(2)
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(10)		(10)		(4)
Energy-related derivatives | MISSISSIPPI POWER CO | Assets held for sale, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					0
Energy-related derivatives | MISSISSIPPI POWER CO | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		0
Energy-related derivatives | SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(3)	(5)	(5)	5
Energy-related derivatives | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(2)		(2)		(7)
Collateral already posted, aggregate fair value	8		8
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(5)		(5)		(8)
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0		0		0
Energy-related derivatives | SOUTHERN Co GAS | Assets held for sale, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)					0
Energy-related derivatives | SOUTHERN Co GAS | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	3		3		$ 1
Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(52)	0	(88)	(2)
Interest rate derivatives | GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(47)	0	(83)	0
Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	(68)	(10)	(107)	(31)
Foreign currency derivatives | SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	$ (68)	$ (10)	$ (107)	$ (31)

Derivatives - Location and Amou

Derivatives - Location and Amount of Gain (Loss) Recognized in Income on Cash Flow and Fair Value Hedging Relationships (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Depreciation and amortization	$ 760	$ 787	$ 2,267	$ 2,338
Total interest expense, net of amounts capitalized	(434)	(458)	(1,294)	(1,386)
Total other income (expense), net	61	57	239	195
Cash Flow Hedging | Gain (loss) on energy-related cash flow hedges | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	0	(5)	2
Cash Flow Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(5)	(5)	(14)	(16)
Cash Flow Hedging | Foreign currency derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(6)	(18)	(18)
Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	(54)	(9)	(62)	(46)
Fair Value Hedging | Interest rate derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	10	(4)	43	(35)
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	120	130	357	370
Total interest expense, net of amounts capitalized	(43)	(45)	(127)	(138)
Total other income (expense), net	6	17	48	22
SOUTHERN POWER CO | Cash Flow Hedging | Gain (loss) on energy-related cash flow hedges | Total depreciation and amortization
Derivative [Line Items]
Gain (loss) on hedge	(1)	0	(5)	2
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Total interest expense, net of amounts capitalized
Derivative [Line Items]
Gain (loss) on hedge	(6)	(6)	(18)	(18)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Total other income (expense), net
Derivative [Line Items]
Gain (loss) on hedge	$ (54)	$ (9)	$ (62)	$ (46)

Derivatives - Cumulative Basis

Derivatives - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Fair Value Hedging - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Securities due within one year
Derivative [Line Items]
Carrying Amount of the Hedged Item	$ (500)	$ (498)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	0	2
Securities due within one year | GEORGIA POWER CO
Derivative [Line Items]
Carrying Amount of the Hedged Item	(500)	(498)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	0	2
Long-term debt
Derivative [Line Items]
Carrying Amount of the Hedged Item	(2,093)	(2,052)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	$ (2)	$ 41

Derivatives - Pre-tax Effects_2

Derivatives - Pre-tax Effects of Derivatives Not Designated as Hedging (Details) - Derivatives not designated as hedging instruments - Energy-related derivatives - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 0	$ (34)	$ 86	$ (74)
Natural gas revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(2)	(36)	81	(79)
Cost of natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 2	$ 2	$ 5	$ 5

Acquisitions and Dispositions -

Acquisitions and Dispositions - Southern Company Narrative (Details) - USD ($) $ in Millions	Jan. 01, 2019	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Jul. 22, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preliminary gain				$ 2,517	$ 324
Impairment charges		$ 18		50
Leveraged leases		799		799				$ 798
Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses, net of cash divested	$ 5,800
Amount of indebtedness assumed at closing	$ 1,300
Disposal Group, Disposed of by Sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale price							$ 71
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charges			$ 32
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure International, Inc. Lighting Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charges		2
Goodwill, intangibles, and other assets impairment charge		18
Disposal Group, Held-for-sale, Not Discontinued Operations | Leverage Lease Investment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Leveraged leases		$ 6		$ 6
Scenario, Forecast | Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preliminary gain						$ 2,500
Preliminary gain, net of tax						1,300
Scenario, Forecast | Disposal Group, Disposed of by Sale, Not Discontinued Operations | PowerSecure International, Inc. Lighting Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale price						8
Scenario, Forecast | Disposal Group, Held-for-sale, Not Discontinued Operations | Leverage Lease Investment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale price						$ 20

Acquisitions and Dispositions_2

Acquisitions and Dispositions - Alabama Power Narrative (Details) - ALABAMA POWER CO - Autauga Combined Cycle Acquisition - MW	Sep. 06, 2019	Sep. 01, 2020
Business Acquisition [Line Items]
Power sales agreement, remaining term	3 years
Scenario, Forecast
Business Acquisition [Line Items]
Approximate nameplate capacity (MW)		885

Acquisitions and Dispositions_3

Acquisitions and Dispositions - Schedule of Acquisition (Details) - SOUTHERN POWER CO - Diamond State Generation Partners $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019MW	Aug. 31, 2019MW	Sep. 30, 2019USD ($)MW
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)	28		28
PPA Contract Period	15 years
Purchase price | $			$ 166
Percentage of operating results consolidated	100.00%
Noncontrolling interest, approximate nameplate capacity	10		10
Approximate nameplate capacity, repowered amount		18
Diamond State Generation Partners | Common Class B
Business Acquisition [Line Items]
Ownership percentage by parent	100.00%		100.00%

Acquisitions and Dispositions_4

Acquisitions and Dispositions - Southern Power Narrative (Details) $ in Millions	Jan. 20, 2020USD ($)	Jun. 13, 2019USD ($)MW	Sep. 30, 2019USD ($)MW	May 31, 2019MW	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Construction work in progress			$ 7,804		$ 7,254
Property, plant, and equipment, subject to lien			117,591		116,914
SOUTHERN POWER CO
Business Acquisition [Line Items]
Construction work in progress			541		430
Property, plant, and equipment, subject to lien			14,397		$ 14,883
SOUTHERN POWER CO | Lien
Business Acquisition [Line Items]
Property, plant, and equipment, subject to lien			545
SOUTHERN POWER CO | Disposal Group, Held-for-sale, Not Discontinued Operations | Mankato expansion | Scenario, Forecast
Business Acquisition [Line Items]
Nacogdoches biomass-fueled facility	$ 650
Gain on termination fee	$ 25
SOUTHERN POWER CO | Disposal Group, Held-for-sale, Not Discontinued Operations | Nacogdoches Biomass-Fueled Facility
Business Acquisition [Line Items]
Approximate nameplate capacity (MW) | MW		115
Nacogdoches biomass-fueled facility		$ 461
After tax gain		$ 88
SOUTHERN POWER CO | Wind Generating Facility
Business Acquisition [Line Items]
Gain on sale			$ 17
SOUTHERN POWER CO | Mankato expansion
Business Acquisition [Line Items]
Approximate nameplate capacity (MW) | MW			385	385
SOUTHERN POWER CO | Series of Construction Projects
Business Acquisition [Line Items]
Construction work in progress			$ 337
SOUTHERN POWER CO | Series of Construction Projects | Minimum
Business Acquisition [Line Items]
Estimated future construction payments			405
SOUTHERN POWER CO | Series of Construction Projects | Maximum
Business Acquisition [Line Items]
Estimated future construction payments			$ 450

Acquisitions and Dispositions_5

Acquisitions and Dispositions - Schedule of Construction Projects (Details) - SOUTHERN POWER CO - MW	1 Months Ended	3 Months Ended
	May 31, 2019	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Aug. 31, 2018	May 31, 2018
Mankato expansion
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)	385			385
PPA Contract Period	20 years
Wild Horse Mountain | Wild Horse Mountain
Business Acquisition [Line Items]
Ownership percentage by parent						100.00%
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%
Scenario, Forecast | Wild Horse Mountain
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)			100
PPA Contract Period			20 years
Scenario, Forecast | Reading
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)		200
PPA Contract Period		12 years

Acquisitions and Dispositions_6

Acquisitions and Dispositions - Assets Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets Held for Sale:
Current assets	$ 17	$ 393
Liabilities Held for Sale:
Current liabilities	6	425
Other non-current liabilities	20	2,836
Disposal Group, Held-for-sale, Not Discontinued Operations
Assets Held for Sale:
Current assets	17	393
Total property, plant, and equipment	551	4,583
Goodwill and other intangible assets	40	40
Other non-current assets	40	727
Total Assets Held for Sale	648	5,743
Liabilities Held for Sale:
Current liabilities	6	425
Other non-current liabilities	20	932
Long-term debt		1,286
Accumulated deferred income taxes		618
Total Liabilities Held for Sale	26	3,261
Disposal Group, Held-for-sale, Not Discontinued Operations | SOUTHERN POWER CO
Assets Held for Sale:
Current assets	12	8
Total property, plant, and equipment	546	536
Goodwill and other intangible assets	40	40
Other non-current assets	14	0
Total Assets Held for Sale	612	584
Liabilities Held for Sale:
Current liabilities	3	15
Other non-current liabilities	0	0
Long-term debt		0
Accumulated deferred income taxes		0
Total Liabilities Held for Sale	$ 3	$ 15

Acquisitions and Dispositions_7

Acquisitions and Dispositions - Pre-tax Profit (Details) - USD ($) $ in Millions	3 Months Ended		5 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 13, 2019	Sep. 30, 2019	Sep. 30, 2018
GULF POWER CO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	$ 0	$ 59		$ 0	$ 146
SOUTHERN POWER CO | Florida Plants
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	0	18		$ 0	40
SOUTHERN POWER CO | Plant Nacogdoches
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Earnings before income taxes	$ 0	$ 7	$ 16		$ 20

Leases - Major Categories of Le

Leases - Major Categories of Lease Obligations (Details) $ in Millions	Sep. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Lease obligations	$ 2,063
Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	988
Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	785
Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	150
Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	51
Other
Lessee, Lease, Description [Line Items]
Lease obligations	89
ALABAMA POWER CO
Lessee, Lease, Description [Line Items]
Lease obligations	163
ALABAMA POWER CO | Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	125
ALABAMA POWER CO | Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	4
ALABAMA POWER CO | Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	2
ALABAMA POWER CO | Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	23
ALABAMA POWER CO | Other
Lessee, Lease, Description [Line Items]
Lease obligations	9
GEORGIA POWER CO
Lessee, Lease, Description [Line Items]
Lease obligations	1,587
GEORGIA POWER CO | Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	1,488
GEORGIA POWER CO | Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	57
GEORGIA POWER CO | Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	3
GEORGIA POWER CO | Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	25
GEORGIA POWER CO | Other
Lessee, Lease, Description [Line Items]
Lease obligations	14
MISSISSIPPI POWER CO
Lessee, Lease, Description [Line Items]
Lease obligations	7
MISSISSIPPI POWER CO | Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	0
MISSISSIPPI POWER CO | Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	2
MISSISSIPPI POWER CO | Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	0
MISSISSIPPI POWER CO | Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	3
MISSISSIPPI POWER CO | Other
Lessee, Lease, Description [Line Items]
Lease obligations	2
SOUTHERN POWER CO
Lessee, Lease, Description [Line Items]
Lease obligations	395
SOUTHERN POWER CO | Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN POWER CO | Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	395
SOUTHERN POWER CO | Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN POWER CO | Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN POWER CO | Other
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN Co GAS
Lessee, Lease, Description [Line Items]
Lease obligations	91
SOUTHERN Co GAS | Electric generating units
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN Co GAS | Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	77
SOUTHERN Co GAS | Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	13
SOUTHERN Co GAS | Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	0
SOUTHERN Co GAS | Other
Lessee, Lease, Description [Line Items]
Lease obligations	$ 1

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)MW
Lessee, Lease, Description [Line Items]
Remaining terms	14 years 4 months 24 days
Minimum lease payments	$ 2,721
Real estate | Maximum
Lessee, Lease, Description [Line Items]
Remaining terms	25 years
Communication towers | Maximum
Lessee, Lease, Description [Line Items]
Lessee, lease term	10 years
Lessee, renewal period	20 years
Fuel cells | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	15 years
GEORGIA POWER CO
Lessee, Lease, Description [Line Items]
Remaining terms	10 years 4 months 24 days
Lease obligations	$ 1,430
Minimum lease payments	$ 1,810
GEORGIA POWER CO | Real estate | Maximum
Lessee, Lease, Description [Line Items]
Remaining terms	25 years
GEORGIA POWER CO | Electric generating units | Affiliate
Lessee, Lease, Description [Line Items]
Lease obligations	$ 625
GEORGIA POWER CO | Electric generating units | Minimum
Lessee, Lease, Description [Line Items]
Remaining terms	3 years
GEORGIA POWER CO | Electric generating units | Maximum
Lessee, Lease, Description [Line Items]
Remaining terms	18 years
GEORGIA POWER CO | Outdoor lighting | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	5 years
SOUTHERN Co GAS
Lessee, Lease, Description [Line Items]
Remaining terms	9 years 7 months 6 days
Lease obligations	$ 91
Minimum lease payments	$ 111
SOUTHERN Co GAS | Maximum
Lessee, Lease, Description [Line Items]
Lessor, remaining term	24 years
SOUTHERN Co GAS | Real estate | Maximum
Lessee, Lease, Description [Line Items]
Remaining terms	25 years
SOUTHERN POWER CO
Lessee, Lease, Description [Line Items]
Remaining terms	33 years 2 months 12 days
Lease obligations	$ 395
Minimum lease payments	$ 947
SOUTHERN POWER CO | Land | Maximum
Lessee, Lease, Description [Line Items]
Lessee, lease term	47 years
SOUTHERN POWER CO | Electric generating units | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	28 years
ALABAMA POWER CO
Lessee, Lease, Description [Line Items]
Remaining terms	3 years 4 months 24 days
Lease obligations	$ 158
PPA, additional generating capacity (in MWs) | MW	640
Minimum lease payments	$ 169
ALABAMA POWER CO | Electric generating units
Lessee, Lease, Description [Line Items]
Minimum lease payments	$ 95
ALABAMA POWER CO | Electric generating units | Minimum
Lessee, Lease, Description [Line Items]
Remaining terms	3 years
ALABAMA POWER CO | Electric generating units | Maximum
Lessee, Lease, Description [Line Items]
Remaining terms	18 years
ALABAMA POWER CO | Outdoor lighting | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	5 years
MISSISSIPPI POWER CO
Lessee, Lease, Description [Line Items]
Remaining terms	6 years 9 months 18 days
Lease obligations	$ 7
Minimum lease payments	$ 8
MISSISSIPPI POWER CO | Electric generating units | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, sales-type lease	20 years
MISSISSIPPI POWER CO | Outdoor lighting | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	5 years
Traditional Electric Operating Companies | Outdoor lighting | Maximum
Lessee, Lease, Description [Line Items]
Lessor, lease term, operating lease	7 years

Leases - Balance Sheet Amounts

Leases - Balance Sheet Amounts Recorded for Operating and Financing Leases (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Operating Leases
Operating lease ROU assets, net, including held for sale	$ 1,823
Operating lease ROU assets, net	1,818
Operating lease obligations - current, including held for sale	229
Operating lease obligations - current	229
Operating lease obligations - non current, including held for sale	1,606
Operating lease obligations - non current	1,601
Total operating lease obligations, including held for sale	1,835
Finance Leases
Finance lease ROU assets, net	220
Finance lease obligations - current	21
Finance lease obligations - noncurrent	207
Total finance lease obligations	228
ALABAMA POWER CO
Operating Leases
Operating lease ROU assets, net	143
Operating lease obligations - current	49
Operating lease obligations - non current	109
Total operating lease obligations	158
Finance Leases
Finance lease ROU assets, net	4
Finance lease obligations - current	1
Finance lease obligations - noncurrent	4
Total finance lease obligations	5
GEORGIA POWER CO
Operating Leases
Operating lease ROU assets, net	1,461
Operating lease obligations - current	143	$ 0
Operating lease obligations - non current	1,287
Total operating lease obligations	1,430
Finance Leases
Finance lease ROU assets, net	134
Finance lease obligations - current	12
Finance lease obligations - noncurrent	145
Total finance lease obligations	157
MISSISSIPPI POWER CO
Operating Leases
Operating lease ROU assets, net	7
Operating lease obligations - current	2
Operating lease obligations - non current	5
Total operating lease obligations	7
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	0
SOUTHERN POWER CO
Operating Leases
Operating lease ROU assets, net	368
Operating lease obligations - current	22
Operating lease obligations - non current	373
Total operating lease obligations	395
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	0
SOUTHERN Co GAS
Operating Leases
Operating lease ROU assets, net	92
Operating lease obligations - current	14
Operating lease obligations - non current	77
Total operating lease obligations	91
Finance Leases
Finance lease ROU assets, net	0
Finance lease obligations - current	0
Finance lease obligations - noncurrent	0
Total finance lease obligations	$ 0

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lease cost
Operating lease cost	$ 94	$ 243
Finance lease cost:
Amortization of ROU assets	7	21
Interest on lease obligations	3	9
Total finance lease cost	10	30
Short-term lease costs	9	39
Variable lease cost	33	81
Sublease income		(1)
Total lease cost	146	392
ALABAMA POWER CO
Lease cost
Operating lease cost	29	49
Finance lease cost:
Amortization of ROU assets	0	1
Interest on lease obligations	0	0
Total finance lease cost	0	1
Short-term lease costs	4	15
Variable lease cost	4	6
Sublease income		(1)
Total lease cost	37	70
GEORGIA POWER CO
Lease cost
Operating lease cost	53	154
Finance lease cost:
Amortization of ROU assets	4	11
Interest on lease obligations	4	14
Total finance lease cost	8	25
Short-term lease costs	5	17
Variable lease cost	26	67
Sublease income		0
Total lease cost	92	263
MISSISSIPPI POWER CO
Lease cost
Operating lease cost	1	2
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	0	0
Sublease income		0
Total lease cost	1	2
SOUTHERN POWER CO
Lease cost
Operating lease cost	7	21
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	1	3
Sublease income		0
Total lease cost	8	24
SOUTHERN Co GAS
Lease cost
Operating lease cost	5	14
Finance lease cost:
Amortization of ROU assets	0	0
Interest on lease obligations	0	0
Total finance lease cost	0	0
Short-term lease costs	0	0
Variable lease cost	0	0
Sublease income		0
Total lease cost	$ 5	$ 14

Leases - Other Information (Det

Leases - Other Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 211
Operating cash flows from finance leases	3
Financing cash flows from finance leases	24
ROU assets obtained in exchange for new operating lease obligations	76
ROU assets obtained in exchange for new finance lease obligations	$ 31
Weighted-average remaining lease term in years:
Operating leases	14 years 4 months 24 days
Finance leases	18 years 10 months 24 days
Weighted-average discount rate:
Operating leases	4.56%
Finance leases	5.07%
ALABAMA POWER CO
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 50
Operating cash flows from finance leases	1
Financing cash flows from finance leases	0
ROU assets obtained in exchange for new operating lease obligations	7
ROU assets obtained in exchange for new finance lease obligations	$ 1
Weighted-average remaining lease term in years:
Operating leases	3 years 4 months 24 days
Finance leases	12 years 4 months 24 days
Weighted-average discount rate:
Operating leases	3.33%
Finance leases	3.65%
GEORGIA POWER CO
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 130
Operating cash flows from finance leases	17
Financing cash flows from finance leases	4
ROU assets obtained in exchange for new operating lease obligations	18
ROU assets obtained in exchange for new finance lease obligations	$ 24
Weighted-average remaining lease term in years:
Operating leases	10 years 4 months 24 days
Finance leases	10 years 9 months 18 days
Weighted-average discount rate:
Operating leases	4.46%
Finance leases	10.74%
MISSISSIPPI POWER CO
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 2
Operating cash flows from finance leases	0
Financing cash flows from finance leases	0
ROU assets obtained in exchange for new operating lease obligations	0
ROU assets obtained in exchange for new finance lease obligations	$ 0
Weighted-average remaining lease term in years:
Operating leases	6 years 9 months 18 days
Weighted-average discount rate:
Operating leases	3.98%
SOUTHERN POWER CO
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 18
Operating cash flows from finance leases	0
Financing cash flows from finance leases	0
ROU assets obtained in exchange for new operating lease obligations	0
ROU assets obtained in exchange for new finance lease obligations	$ 0
Weighted-average remaining lease term in years:
Operating leases	33 years 2 months 12 days
Weighted-average discount rate:
Operating leases	5.68%
SOUTHERN Co GAS
Cash paid for amounts included in the measurements of lease obligations:
Operating cash flows from operating leases	$ 13
Operating cash flows from finance leases	0
Financing cash flows from finance leases	0
ROU assets obtained in exchange for new operating lease obligations	14
ROU assets obtained in exchange for new finance lease obligations	$ 0
Weighted-average remaining lease term in years:
Operating leases	9 years 7 months 6 days
Weighted-average discount rate:
Operating leases	3.73%

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Millions	Sep. 30, 2019USD ($)
Operating leases:
2019 (remaining)	$ 45
2020	284
2021	269
2022	259
2023	202
Thereafter	1,662
Total	2,721
Less: Present value discount	886
Operating lease obligations, including held for sale	1,835
Finance leases:
2019 (remaining)	9
2020	31
2021	24
2022	21
2023	17
Thereafter	259
Total	361
Less: Present value discount	133
Finance lease obligations	228
ALABAMA POWER CO
Operating leases:
2019 (remaining)	4
2020	54
2021	53
2022	52
2023	4
Thereafter	2
Total	169
Less: Present value discount	11
Operating lease obligations	158
Finance leases:
2019 (remaining)	0
2020	1
2021	1
2022	1
2023	1
Thereafter	1
Total	5
Less: Present value discount	0
Finance lease obligations	5
GEORGIA POWER CO
Operating leases:
2019 (remaining)	23
2020	205
2021	198
2022	196
2023	197
Thereafter	991
Total	1,810
Less: Present value discount	380
Operating lease obligations	1,430
Finance leases:
2019 (remaining)	4
2020	28
2021	24
2022	24
2023	25
Thereafter	161
Total	266
Less: Present value discount	109
Finance lease obligations	157
MISSISSIPPI POWER CO
Operating leases:
2019 (remaining)	1
2020	2
2021	1
2022	1
2023	1
Thereafter	2
Total	8
Less: Present value discount	1
Operating lease obligations	7
Finance leases:
2019 (remaining)	0
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	0
Less: Present value discount
Finance lease obligations	0
SOUTHERN POWER CO
Operating leases:
2019 (remaining)	8
2020	22
2021	23
2022	23
2023	24
Thereafter	847
Total	947
Less: Present value discount	552
Operating lease obligations	395
Finance leases:
2019 (remaining)	0
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	0
Less: Present value discount
Finance lease obligations	0
SOUTHERN Co GAS
Operating leases:
2019 (remaining)	4
2020	17
2021	17
2022	13
2023	11
Thereafter	49
Total	111
Less: Present value discount	20
Operating lease obligations	91
Finance leases:
2019 (remaining)	0
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	0
Less: Present value discount	0
Finance lease obligations	$ 0

Leases - Leases Not Yet Commenc

Leases - Leases Not Yet Commenced (Details) $ in Millions	Sep. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Estimated total obligations	$ 159
ALABAMA POWER CO
Lessee, Lease, Description [Line Items]
Estimated total obligations	95
SOUTHERN POWER CO
Lessee, Lease, Description [Line Items]
Estimated total obligations	$ 64
Minimum
Lessee, Lease, Description [Line Items]
Longest lease term expiration	28 years
Maximum
Lessee, Lease, Description [Line Items]
Longest lease term expiration	31 years
Maximum | ALABAMA POWER CO
Lessee, Lease, Description [Line Items]
Longest lease term expiration	28 years
Maximum | SOUTHERN POWER CO
Lessee, Lease, Description [Line Items]
Longest lease term expiration	31 years

Leases - Lease Income (Details)

Leases - Lease Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 2	$ 7
Lease income - operating leases	64	216
Variable lease income	141	324
Total lease income	207	547
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	6	19
Variable lease income	0	0
Total lease income	6	19
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	18	57
Variable lease income	0	0
Total lease income	18	57
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	7
Lease income - operating leases	0	0
Variable lease income	0	0
Total lease income	2	7
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	31	111
Variable lease income	151	349
Total lease income	182	460
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	9	26
Variable lease income	0	0
Total lease income	$ 9	$ 26

Leases - Undiscounted Cash Flow

Leases - Undiscounted Cash Flows to be Received Under Tolling Arrangements Accounted for as Sales-type Leases (Details) $ in Millions	Sep. 30, 2019USD ($)
Lessor, Lease, Description [Line Items]
2019 (remaining)	$ 4
2020	17
2021	15
2022	15
2023	14
Thereafter	152
Total undiscounted cash flows	217
Lease receivable	119
Difference between undiscounted cash flows and discounted cash flows	98
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
2019 (remaining)	4
2020	17
2021	15
2022	15
2023	14
Thereafter	152
Total undiscounted cash flows	217
Lease receivable	119
Difference between undiscounted cash flows and discounted cash flows	$ 98

Leases - Undiscounted Cash Fl_2

Leases - Undiscounted Cash Flows to be Received Under PPAs Accounted for as Operating Leases (Details) $ in Millions	Sep. 30, 2019USD ($)
Lessor, Lease, Description [Line Items]
2019 (remaining)	$ 39
2020	155
2021	140
2022	121
2023	109
Thereafter	1,166
Total	1,730
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
2019 (remaining)	6
2020	26
2021	22
2022	13
2023	5
Thereafter	22
Total	94
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
2019 (remaining)	7
2020	26
2021	18
2022	8
2023	2
Thereafter	0
Total	61
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
2019 (remaining)	8
2020	65
2021	66
2022	68
2023	69
Thereafter	350
Total	626
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
2019 (remaining)	9
2020	35
2021	35
2022	34
2023	34
Thereafter	497
Total	$ 644

Segment and Related Informati_3

Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)state	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)statepipelinesegment	Sep. 30, 2018USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	3		3
Total operating revenues	$ 5,995	$ 6,159	$ 16,505	$ 18,158
Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	498	492	2,661	2,806
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Total operating revenues	574	635	1,527	1,699
SOUTHERN POWER CO | Wholesale revenues, affiliates
Segment Reporting Information [Line Items]
Total operating revenues	$ 116	134	$ 320	326
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	4		4
Total operating revenues	$ 498	492	$ 2,661	2,861
Number of reportable segments | segment			4
SOUTHERN Co GAS | Pipeline
Segment Reporting Information [Line Items]
Number of pipeline construction projects | pipeline			2
SOUTHERN Co GAS | SNG
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%		50.00%
SOUTHERN Co GAS | Dalton Pipeline
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%		50.00%
SOUTHERN Co GAS | Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	$ 498	487	$ 2,661	2,829
SOUTHERN Co GAS | Traditional Electric Operating Companies | Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	9	14	13	22
SOUTHERN Co GAS | SOUTHERN POWER CO | Natural gas
Segment Reporting Information [Line Items]
Total operating revenues	$ 20	$ 38	$ 53	$ 96

Segment and Related Informati_4

Segment and Related Information - Financial Data for Business Segments (Details) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Sep. 30, 2018USD ($)utility	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)utility	Dec. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Operating revenues	$ 5,995			$ 6,159			$ 16,505	$ 18,158
Segment net income (loss)	1,316	$ 899	$ 2,084	1,164	$ (154)	$ 938	4,298	1,948
Goodwill	5,280						5,280		$ 5,315
Total assets	117,591						117,591		116,914
Impairment charges	18						50
Impairment charges	110			36			142	197
Gain on dispositions, net	6			353			2,512	317
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	574			635			1,527	1,699
Segment net income (loss)	86	174	56	92	22	121	316	235
Total assets	14,397						14,397		14,883
Impairment charges	0			36			0	155
Impairment charge, net of tax				27				116
Gain on dispositions, net	0			0			23	0
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Plant Nacogdoches
Segment Reporting Information [Line Items]
Pre-tax gain on the sale of Plant Nacogdoches							23
Gain on the sale of Plant Nacogdoches, after tax							88
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	498			492			2,661	2,861
Segment net income (loss)	(29)	$ 106	$ 270	46	$ (31)	$ 279	347	294
Goodwill	5,015						5,015		5,015
Total assets	21,047						21,047		21,448
Impairment charges	92			0			92	42
Gain on dispositions, net	0			$ 353			0	$ 317
SOUTHERN Co GAS | Natural Gas Storage Facility
Segment Reporting Information [Line Items]
Impairment charges							92
Impairment charge, net of tax							65
SOUTHERN Co GAS | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment Reporting Information [Line Items]
Number of natural gas distribution utilities disposed | utility				3				3
SOUTHERN Co GAS | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Pivotal Home Solutions
Segment Reporting Information [Line Items]
Gain on dispositions, net				$ 353				$ 317
Gain (loss) on dispositions, after tax				40				(35)
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	5,363			5,509			13,448	14,456
Segment net income (loss)	1,459			1,240			3,035	1,946
Goodwill	2						2		2
Total assets	94,134						94,134		93,959
Traditional Electric Operating Companies | GEORGIA POWER AND MISSISSIPPI POWER CO | Kemper County Energy Facility
Segment Reporting Information [Line Items]
Public utilities, property, plant and equipment, amount of loss (recovery) on plant abandonment	4			1			10	1,100
Public utilities, property, plant and equipment, amount of loss (recovery) on plant abandonment after tax	3			1			7	800
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	498			492			2,661	2,861
SOUTHERN Co GAS | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Pivotal Home Solutions
Segment Reporting Information [Line Items]
Impairment charges								42
All Other | Disposal Group, Disposed of by Sale, Not Discontinued Operations | GULF POWER CO
Segment Reporting Information [Line Items]
Preliminary pre-tax gain (reduction)	(4)						2,500
Preliminary after-tax gain (reduction)	4						1,300
Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	4,034						4,034		4,034
Gas Distribution Operations | SOUTHERN Co GAS | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment Reporting Information [Line Items]
Operating revenues				8				245
Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	981						981		981
Gain on dispositions, net								(34)
Operating revenues								55
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	493			485			2,670	2,866
Segment net income (loss)	30			68			406	352
Total assets	21,641						21,641		21,918
Operating Segments | Traditional Electric Operating Companies | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,908			5,014			12,252	13,117
Segment net income (loss)	1,373			1,148			2,719	1,711
Goodwill	0						0		0
Total assets	80,493						80,493		79,382
Operating Segments | SOUTHERN POWER CO | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	574			635			1,527	1,699
Segment net income (loss)	86			92			316	235
Goodwill	2						2		2
Total assets	14,397						14,397		14,883
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	498			492			2,661	2,861
Segment net income (loss)	(29)			46			347	294
Goodwill	5,015						5,015		5,015
Total assets	21,047						21,047		21,448
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	146			202			514	984
Segment net income (loss)	(110)			(119)			931	(292)
Goodwill	263						263		298
Total assets	3,569						3,569		3,285
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	10			13			34	39
Segment net income (loss)	(59)			(22)			(59)	(58)
Total assets	10,429						10,429		11,112
Operating Segments | Gas Distribution Operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	448			441			2,188	2,297
Segment net income (loss)	37			74			228	290
Total assets	17,798						17,798		17,266
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8			8			24	24
Segment net income (loss)	6			20			63	68
Total assets	1,743						1,743		1,763
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(2)			(8)			132	142
Segment net income (loss)	(9)			(18)			61	65
Total assets	657						657		1,302
Less Gross Gas Costs	1,212			1,663			4,378	5,057
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS | Third Party Gross Revenues
Segment Reporting Information [Line Items]
Operating revenues	1,138			1,573			4,287	4,847
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS | Intercompany Revenues
Segment Reporting Information [Line Items]
Operating revenues	72			82			223	352
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS | Total Gross Revenues
Segment Reporting Information [Line Items]
Operating revenues	1,210			1,655			4,510	5,199
Operating Segments | Gas Marketing Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	39			44			326	403
Segment net income (loss)	(4)			(8)			54	(71)
Total assets	1,443						1,443		1,587
Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(12)			(44)			(118)	(143)
Segment net income (loss)	(4)			(3)			(15)	0
Goodwill	0						0		0
Total assets	(1,159)						(1,159)		(1,778)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(5)			(6)			(43)	(44)
Segment net income (loss)	0			0			0	0
Total assets	(11,023)						(11,023)		(11,582)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(119)			(140)			(331)	(360)
Segment net income (loss)	0			$ 0			0	$ 0
Goodwill	0						0		0
Total assets	$ (756)						$ (756)		$ (306)

Segment and Related Informati_5

Segment and Related Information - Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Operating revenues	$ 5,995	$ 6,159	$ 16,505	$ 18,158
Retail
Concentration Risk [Line Items]
Operating revenues	4,512	4,605	11,136	11,913
Wholesale
Concentration Risk [Line Items]
Operating revenues	625	698	1,667	1,937
Other
Concentration Risk [Line Items]
Operating revenues	163	165	492	495
Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	445	433	2,169	2,299
Electric Utilities' Revenues
Concentration Risk [Line Items]
Operating revenues	5,363	5,509	13,448	14,456
Electric Utilities' Revenues | Retail
Concentration Risk [Line Items]
Operating revenues	4,512	4,605	11,136	11,913
Electric Utilities' Revenues | Wholesale
Concentration Risk [Line Items]
Operating revenues	625	698	1,667	1,937
Electric Utilities' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	226	206	645	606
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	498	492	2,661	2,861
Southern Company Gas' Revenues | Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	445	438	2,169	2,276
Southern Company Gas' Revenues | Gas Distribution Operations | Revenues | Product Concentration Risk | Three Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues		7		245
Southern Company Gas' Revenues | Gas Marketing Services
Concentration Risk [Line Items]
Operating revenues	39	44	326	403
Southern Company Gas' Revenues | Gas Marketing Services | Revenues | Product Concentration Risk | Pivotal Home Solutions
Concentration Risk [Line Items]
Operating revenues				55
Southern Company Gas' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	$ 14	$ 10	$ 166	$ 182