Alabama Power (ALP-PQ) 10-Q 2 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Jun. 30, 2017shares
Document Information [Line Items]
Entity Registrant Name	SOUTHERN CO
Entity Central Index Key	92,122
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	999,474,028
ALABAMA POWER CO
Document Information [Line Items]
Entity Registrant Name	ALABAMA POWER CO
Entity Central Index Key	3,153
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	30,537,500
GEORGIA POWER CO
Document Information [Line Items]
Entity Registrant Name	GEORGIA POWER CO
Entity Central Index Key	41,091
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	9,261,500
GULF POWER CO
Document Information [Line Items]
Entity Registrant Name	GULF POWER CO
Entity Central Index Key	44,545
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	7,392,717
MISSISSIPPI POWER CO
Document Information [Line Items]
Entity Registrant Name	MISSISSIPPI POWER CO
Entity Central Index Key	66,904
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	1,121,000
SOUTHERN POWER CO
Document Information [Line Items]
Entity Registrant Name	SOUTHERN POWER CO
Entity Central Index Key	1,160,661
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	1,000
SOUTHERN Co GAS
Document Information [Line Items]
Entity Registrant Name	SOUTHERN Co GAS
Entity Central Index Key	1,004,155
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	100

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Revenues:
Retail electric revenues	$ 3,777	$ 3,748	$ 7,171	$ 7,124
Wholesale electric revenues	618	446	1,149	842
Other electric revenues	167	166	342	348
Natural gas revenues	684	0	2,214	0
Other revenues	184	99	326	137
Total operating revenues	5,430	4,459	11,202	8,451
Operating Expenses:
Fuel	1,092	1,023	2,088	1,934
Purchased power	211	189	390	354
Cost of natural gas	232	0	951	0
Cost of other sales	114	58	203	77
Other operations and maintenance	1,301	1,099	2,631	2,206
Depreciation and amortization	754	569	1,469	1,110
Taxes other than income taxes	308	255	638	511
Estimated loss on Kemper IGCC	3,012	81	3,120	134
Total operating expenses	7,024	3,274	11,490	6,326
Operating Income (Loss)	(1,594)	1,185	(288)	2,125
Other Income and (Expense):
Allowance for equity funds used during construction	58	45	115	98
Earnings (loss) from equity method investments	28	(1)	67	(1)
Interest expense, net of amounts capitalized	(424)	(293)	(840)	(539)
Other income (expense), net	(3)	(28)	(11)	(56)
Total other income and (expense)	(341)	(277)	(669)	(498)
Earnings (Loss) Before Income Taxes	(1,935)	908	(957)	1,627
Income taxes (benefit)	(587)	261	(273)	479
Consolidated Net Income (Loss)	(1,348)	647	(684)	1,148
Dividends on preferred and preference stock of subsidiaries	11	12	22	23
Net income attributable to noncontrolling interests	22	12	17	13
Net Income	$ (1,381)	$ 623	$ (723)	$ 1,112
Earnings (loss) per share —
Basic (in dollars per share)	$ (1.38)	$ 0.67	$ (0.73)	$ 1.20
Diluted (in dollars per share)	$ (1.37)	$ 0.66	$ (0.72)	$ 1.20
Average number of shares of common stock outstanding (in millions)
Basic (in shares)	998	934	996	925
Diluted (in shares)	1,005	940	1,003	931
Cash dividends paid per share of common stock (in dollars per share)	$ 0.58	$ 0.56	$ 1.14	$ 1.1025
SOUTHERN POWER CO
Operating Revenues:
Wholesale revenues, non-affiliates	$ 436	$ 264	$ 783	$ 480
Wholesale revenues, affiliates	90	107	190	204
Other revenues	3	2	6	4
Total operating revenues	529	373	979	688
Operating Expenses:
Fuel	139	96	271	187
Purchased power, non-affiliates	29	21	54	35
Purchased power, affiliates	11	2	16	8
Other operations and maintenance	97	86	190	162
Depreciation and amortization	129	81	247	154
Taxes other than income taxes	12	6	24	13
Total operating expenses	417	292	802	559
Operating Income (Loss)	112	81	177	129
Other Income and (Expense):
Interest expense, net of amounts capitalized	(48)	(22)	(97)	(43)
Other income (expense), net	2	1	(2)	1
Total other income and (expense)	(46)	(21)	(99)	(42)
Earnings (Loss) Before Income Taxes	66	60	78	87
Income taxes (benefit)	(38)	(41)	(90)	(65)
Consolidated Net Income (Loss)	104	101	168	152
Net income attributable to noncontrolling interests	22	12	17	13
Net Income	82	89	151	139
ALABAMA POWER CO
Operating Revenues:
Retail electric revenues	1,333	1,316	2,560	2,510
Wholesale revenues, non-affiliates	68	67	133	130
Wholesale revenues, affiliates	32	9	65	31
Other revenues	51	52	108	105
Total operating revenues	1,484	1,444	2,866	2,776
Operating Expenses:
Fuel	303	295	601	564
Purchased power, non-affiliates	40	40	75	76
Purchased power, affiliates	34	55	62	88
Other operations and maintenance	375	355	743	747
Depreciation and amortization	183	175	364	347
Taxes other than income taxes	95	94	191	191
Total operating expenses	1,030	1,014	2,036	2,013
Operating Income (Loss)	454	430	830	763
Other Income and (Expense):
Allowance for equity funds used during construction	8	6	16	16
Interest expense, net of amounts capitalized	(77)	(74)	(153)	(147)
Other income (expense), net	1	(4)	(4)	(11)
Total other income and (expense)	(68)	(72)	(141)	(142)
Earnings (Loss) Before Income Taxes	386	358	689	621
Income taxes (benefit)	151	140	277	242
Consolidated Net Income (Loss)	235	218	412	379
Dividends on preferred and preference stock of subsidiaries	5	5	9	9
Net Income	230	213	403	370
GEORGIA POWER CO
Operating Revenues:
Retail electric revenues	1,904	1,907	3,593	3,624
Wholesale revenues, non-affiliates	40	40	79	82
Wholesale revenues, affiliates	9	10	17	15
Other revenues	95	94	191	202
Total operating revenues	2,048	2,051	3,880	3,923
Operating Expenses:
Fuel	445	439	815	815
Purchased power, non-affiliates	103	92	191	175
Purchased power, affiliates	138	111	310	250
Other operations and maintenance	399	439	781	896
Depreciation and amortization	223	214	444	425
Taxes other than income taxes	101	100	199	197
Total operating expenses	1,409	1,395	2,740	2,758
Operating Income (Loss)	639	656	1,140	1,165
Other Income and (Expense):
Allowance for equity funds used during construction			25	24
Interest expense, net of amounts capitalized	(104)	(99)	(205)	(193)
Other income (expense), net	16	8	36	26
Total other income and (expense)	(88)	(91)	(169)	(167)
Earnings (Loss) Before Income Taxes	551	565	971	998
Income taxes (benefit)	199	211	355	371
Consolidated Net Income (Loss)	352	354	616	627
Dividends on preferred and preference stock of subsidiaries	5	5	9	9
Net Income	347	349	607	618
GULF POWER CO
Operating Revenues:
Retail electric revenues	318	319	596	602
Wholesale revenues, non-affiliates	12	15	30	31
Wholesale revenues, affiliates	10	15	47	36
Other revenues	17	16	34	31
Total operating revenues	357	365	707	700
Operating Expenses:
Fuel	88	107	196	201
Purchased power, non-affiliates	35	32	67	62
Purchased power, affiliates	9	4	11	5
Other operations and maintenance	87	77	171	155
Depreciation and amortization	35	42	53	80
Taxes other than income taxes	28	29	55	58
Loss on Plant Scherer Unit 3	0	0	33	0
Total operating expenses	282	291	586	561
Operating Income (Loss)	75	74	121	139
Other Income and (Expense):
Interest expense, net of amounts capitalized	(13)	(12)	(24)	(25)
Other income (expense), net	(1)	(1)	(2)	(2)
Total other income and (expense)	(14)	(13)	(26)	(27)
Earnings (Loss) Before Income Taxes	61	61	95	112
Income taxes (benefit)	24	24	38	44
Consolidated Net Income (Loss)	37	37	57	68
Dividends on preferred and preference stock of subsidiaries	2	3	4	5
Net Income	35	34	53	63
MISSISSIPPI POWER CO
Operating Revenues:
Retail electric revenues	222	206	422	389
Wholesale revenues, non-affiliates	62	60	124	120
Wholesale revenues, affiliates	15	7	20	16
Other revenues	4	4	9	8
Total operating revenues	303	277	575	533
Operating Expenses:
Fuel	102	81	180	157
Purchased power, non-affiliates	2	1	3	1
Purchased power, affiliates	4	4	11	9
Other operations and maintenance	70	68	144	136
Depreciation and amortization	41	45	81	84
Taxes other than income taxes	26	25	52	50
Estimated loss on Kemper IGCC	3,012	81	3,120	134
Total operating expenses	3,257	305	3,591	571
Operating Income (Loss)	(2,954)	(28)	(3,016)	(38)
Other Income and (Expense):
Allowance for equity funds used during construction	36	30	71	59
Interest expense, net of amounts capitalized	(17)	(15)	(37)	(31)
Other income (expense), net	1	(1)	1	(3)
Total other income and (expense)	20	14	35	25
Earnings (Loss) Before Income Taxes	(2,934)	(14)	(2,981)	(13)
Income taxes (benefit)	(881)	(17)	(908)	(27)
Consolidated Net Income (Loss)	(2,053)	3	(2,073)	14
Dividends on preferred and preference stock of subsidiaries	1	1	1	1
Net Income	(2,054)	2	(2,074)	13
SOUTHERN Co GAS
Operating Revenues:
Natural gas revenues	684		2,214
Other revenues	32		62
Total operating revenues	716		2,276
Operating Expenses:
Cost of natural gas	232		951
Cost of other sales	6		13
Other operations and maintenance	213		467
Depreciation and amortization	125		244
Merger-related expenses	0		0
Taxes other than income taxes	44		114
Total operating expenses	620		1,789
Operating Income (Loss)	96		487
Other Income and (Expense):
Earnings (loss) from equity method investments	29		68
Interest expense, net of amounts capitalized	(48)		(94)
Other income (expense), net	3		7
Total other income and (expense)	(16)		(19)
Earnings (Loss) Before Income Taxes	80		468
Income taxes (benefit)	31		180
Consolidated Net Income (Loss)	49		288
Net income attributable to noncontrolling interests	0		0
Net Income	$ 49		$ 288
Predecessor | SOUTHERN Co GAS
Operating Revenues:
Natural gas revenues		539		1,841
Other revenues		32		64
Total operating revenues		571		1,905
Operating Expenses:
Cost of natural gas		184		755
Cost of other sales		7		14
Other operations and maintenance		213		454
Depreciation and amortization		104		206
Merger-related expenses		53		56
Taxes other than income taxes		37		99
Total operating expenses		598		1,584
Operating Income (Loss)		(27)		321
Other Income and (Expense):
Earnings (loss) from equity method investments		1		2
Interest expense, net of amounts capitalized		(48)		(96)
Other income (expense), net		2		5
Total other income and (expense)		(45)		(89)
Earnings (Loss) Before Income Taxes		(72)		232
Income taxes (benefit)		(24)		87
Consolidated Net Income (Loss)		(48)		145
Net income attributable to noncontrolling interests		3		14
Net Income		$ (51)		$ 131

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Income (Unaudited) - Parenthetical - SOUTHERN Co GAS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Excise taxes collected	$ 19		$ 67
Predecessor
Excise taxes collected		$ 17		$ 57

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net Income	$ (1,348)	$ 647	$ (684)	$ 1,148
Qualifying hedges:
Changes in fair value, net of tax	38	(20)	29	(137)
Reclassification adjustment for amounts included in net income, net of tax	(41)	16	(42)	18
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	1	1	2	2
Total other comprehensive income (loss)	(2)	(3)	(11)	(117)
Comprehensive Income (Loss)	(1,350)	644	(695)	1,031
Dividends on preferred and preference stock of subsidiaries	11	12	22	23
Comprehensive income attributable to noncontrolling interests	22	12	17	13
Comprehensive Income (Loss) Attributable to Parent	(1,383)	620	(734)	995
ALABAMA POWER CO
Net Income	235	218	412	379
Qualifying hedges:
Changes in fair value, net of tax	0	0	0	(2)
Reclassification adjustment for amounts included in net income, net of tax	1	1	2	2
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	1	1	2	0
Comprehensive Income (Loss)	236	219	414	379
Dividends on preferred and preference stock of subsidiaries	5	5	9	9
GEORGIA POWER CO
Net Income	352	354	616	627
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax	1	1	2	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	1	1	2	1
Comprehensive Income (Loss)	353	355	618	628
Dividends on preferred and preference stock of subsidiaries	5	5	9	9
GULF POWER CO
Net Income	37	37	57	68
Qualifying hedges:
Changes in fair value, net of tax	(1)	(1)	(1)	(4)
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	(1)	(1)	(1)	(4)
Comprehensive Income (Loss)	36	36	56	64
Dividends on preferred and preference stock of subsidiaries	2	3	4	5
MISSISSIPPI POWER CO
Net Income	(2,053)	3	(2,073)	14
Qualifying hedges:
Changes in fair value, net of tax	0	0	1	0
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	0	0	1	0
Comprehensive Income (Loss)	(2,053)	3	(2,072)	14
Dividends on preferred and preference stock of subsidiaries	1	1	1	1
SOUTHERN POWER CO
Net Income	104	101	168	152
Qualifying hedges:
Changes in fair value, net of tax	40	(24)	32	(24)
Reclassification adjustment for amounts included in net income, net of tax	(45)	13	(48)	14
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)	(5)	(11)	(16)	(10)
Comprehensive Income (Loss)	99	90	152	142
Comprehensive income attributable to noncontrolling interests	22	12	17	13
Comprehensive Income (Loss) Attributable to Parent	77	78	135	129
SOUTHERN Co GAS
Net Income	49		288
Qualifying hedges:
Changes in fair value, net of tax	(1)		(2)
Reclassification adjustment for amounts included in net income, net of tax	0		0
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax	0		(1)
Total other comprehensive income (loss)	(1)		(3)
Comprehensive Income (Loss)	48		285
Comprehensive income attributable to noncontrolling interests	0		0
Comprehensive Income (Loss) Attributable to Parent	$ 48		$ 285
Predecessor | SOUTHERN Co GAS
Net Income		(48)		145
Qualifying hedges:
Changes in fair value, net of tax		(12)		(41)
Reclassification adjustment for amounts included in net income, net of tax		2		1
Pension and other postretirement benefit plans:
Reclassification adjustment for amounts included in net income, net of tax		2		5
Total other comprehensive income (loss)		(8)		(35)
Comprehensive Income (Loss)		(56)		110
Comprehensive income attributable to noncontrolling interests		3		14
Comprehensive Income (Loss) Attributable to Parent		$ (59)		$ 96

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in fair value, tax	$ 23	$ (13)	$ 17	$ (85)
Reclassification adjustment for qualified hedges, tax	(25)	10	(26)	11
Reclassification adjustment for pension and other post retirement benefit plans, tax	1	0	1	1
ALABAMA POWER CO
Changes in fair value, tax	0	0	0	(1)
Reclassification adjustment for qualified hedges, tax	1	0	1	1
GEORGIA POWER CO
Reclassification adjustment for qualified hedges, tax	0	0	1	1
GULF POWER CO
Changes in fair value, tax	0	(1)	(1)	(3)
MISSISSIPPI POWER CO
Changes in fair value, tax	0	0	0	0
SOUTHERN POWER CO
Changes in fair value, tax	24	(15)	20	(15)
Reclassification adjustment for qualified hedges, tax	(27)	8	(30)	8
SOUTHERN Co GAS
Changes in fair value, tax	(1)		(2)
Reclassification adjustment for qualified hedges, tax	0		0
Reclassification adjustment for pension and other post retirement benefit plans, tax	$ 0		$ 0
Predecessor | SOUTHERN Co GAS
Changes in fair value, tax		(7)		(23)
Reclassification adjustment for qualified hedges, tax		0		0
Reclassification adjustment for pension and other post retirement benefit plans, tax		$ 2		$ 4

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities:
Net Income	$ (684)	$ 1,148
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	1,683	1,306
Deferred income taxes	(270)	279
Allowance for equity funds used during construction	(115)	(98)
Pension, postretirement, and other employee benefits	(83)	(56)
Settlement of asset retirement obligations	(87)	(66)
Stock based compensation expense	73	69
Hedge settlements	1	(201)
Estimated loss on Kemper IGCC	3,120	134
Income taxes receivable, non-current	(58)	0
Other, net	(63)	63
Changes in certain current assets and liabilities —
-Receivables	110	(197)
-Prepayments	(61)	(28)
-Fossil fuel stock	6	70
-Natural gas for sale, net of temporary LIFO liquidation	223	0
-Other current assets	(36)	(25)
-Accounts payable	(353)	(71)
-Accrued taxes	(132)	74
-Accrued compensation	(331)	(222)
-Retail fuel cost over recovery	(187)	(54)
-Other current liabilities	(14)	15
Net cash provided from operating activities	2,742	2,140
Investing Activities:
Business acquisitions, net of cash acquired	(1,062)	(897)
Property additions	(3,398)	(3,486)
Investment in restricted cash	(16)	(8,608)
Distribution of restricted cash	27	649
Nuclear decommissioning trust fund purchases	(388)	(585)
Nuclear decommissioning trust fund sales	383	580
Cost of removal, net of salvage	(128)	(99)
Change in construction payables, net	(117)	(260)
Investment in unconsolidated subsidiaries	(116)	0
Payments pursuant to LTSAs	(132)	(82)
Other investing activities	58	113
Net cash used for investing activities	(4,889)	(12,675)
Financing Activities:
Increase (decrease) in notes payable, net	30	471
Proceeds —
Long-term debt	2,958	12,038
Common stock	417	1,383
Short-term borrowings	1,004	0
Redemptions and repurchases —
Long-term debt	(1,478)	(1,272)
Preference stock	(150)	0
Short-term borrowings	0	(475)
Distributions to noncontrolling interests	(40)	(11)
Capital contributions from noncontrolling interests	73	179
Purchase of membership interests from noncontrolling interests	0	(129)
Payment of common stock dividends	(1,134)	(1,023)
Other financing activities	(75)	(133)
Net cash provided from financing activities	1,605	11,028
Net Change in Cash and Cash Equivalents	(542)	493
Cash and Cash Equivalents at Beginning of Period	1,975	1,404
Cash and Cash Equivalents at End of Period	1,433	1,897
Cash paid (received) during the period for —
Interest	833	458
Income taxes, net	1	(138)
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	629	549
ALABAMA POWER CO
Operating Activities:
Net Income	412	379
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	442	419
Deferred income taxes	192	175
Allowance for equity funds used during construction	(16)	(16)
Pension, postretirement, and other employee benefits	(24)	(23)
Other, net	4	(33)
Changes in certain current assets and liabilities —
-Receivables	(58)	64
-Fossil fuel stock	13	(32)
-Other current assets	(75)	(67)
-Accounts payable	(154)	(75)
-Accrued taxes	52	102
-Accrued compensation	(74)	(50)
-Retail fuel cost over recovery	(65)	(60)
-Other current liabilities	7	8
Net cash provided from operating activities	672	807
Investing Activities:
Property additions	(738)	(645)
Nuclear decommissioning trust fund purchases	(117)	(200)
Nuclear decommissioning trust fund sales	117	200
Cost of removal, net of salvage	(54)	(51)
Change in construction payables, net	48	(27)
Other investing activities	(15)	(18)
Net cash used for investing activities	(759)	(741)
Proceeds —
Senior notes	550	400
Capital contributions from parent company	327	237
Other long-term debt	0	45
Redemptions and repurchases —
Redemptions — Senior notes	(200)	(200)
Payment of common stock dividends	(357)	(382)
Other financing activities	(14)	(17)
Net cash provided from financing activities	306	83
Net Change in Cash and Cash Equivalents	219	149
Cash and Cash Equivalents at Beginning of Period	420	194
Cash and Cash Equivalents at End of Period	639	343
Cash paid (received) during the period for —
Interest	140	131
Income taxes, net	88	(122)
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	132	94
GEORGIA POWER CO
Operating Activities:
Net Income	616	627
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	543	530
Deferred income taxes	159	157
Allowance for equity funds used during construction	(25)	(24)
Deferred expenses	41	39
Pension, postretirement, and other employee benefits	(45)	(28)
Settlement of asset retirement obligations	(62)	(52)
Other, net	(39)	36
Changes in certain current assets and liabilities —
-Receivables	(150)	(25)
-Fossil fuel stock	(32)	61
-Other current assets	(22)	10
-Accounts payable	(153)	6
-Accrued taxes	(194)	(137)
-Accrued compensation	(65)	(44)
-Retail fuel cost over recovery	(84)	1
-Other current liabilities	(6)	16
Net cash provided from operating activities	482	1,173
Investing Activities:
Property additions	(1,284)	(1,058)
Nuclear decommissioning trust fund purchases	(271)	(386)
Nuclear decommissioning trust fund sales	266	380
Cost of removal, net of salvage	(32)	(34)
Change in construction payables, net of joint owner portion	1	(75)
Payments pursuant to LTSAs	(56)	(14)
Sale of property	63	0
Other investing activities	(12)	17
Net cash used for investing activities	(1,325)	(1,170)
Financing Activities:
Increase (decrease) in notes payable, net	37	39
Proceeds —
Senior notes	850	650
FFB loan	0	300
Capital contributions from parent company	380	239
Short-term borrowings	800	0
Redemptions and repurchases —
Pollution control revenue bonds	(27)	(4)
Redemptions — Senior notes	(450)	(500)
Payment of common stock dividends	(640)	(653)
Other financing activities	(19)	(20)
Net cash provided from financing activities	931	51
Net Change in Cash and Cash Equivalents	88	54
Cash and Cash Equivalents at Beginning of Period	3	67
Cash and Cash Equivalents at End of Period	91	121
Cash paid (received) during the period for —
Interest	186	174
Income taxes, net	213	78
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	348	288
GULF POWER CO
Operating Activities:
Net Income	57	68
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	56	83
Deferred income taxes	19	16
Loss on Plant Scherer Unit 3	33	0
Other, net	(4)	(3)
Changes in certain current assets and liabilities —
-Receivables	(25)	(6)
-Fossil fuel stock	4	34
-Other current assets	10	1
-Accrued taxes	7	17
-Accrued compensation	(17)	(12)
-Over recovered regulatory clause revenues	(19)	5
-Other current liabilities	3	(7)
Net cash provided from operating activities	124	196
Investing Activities:
Property additions	(97)	(68)
Cost of removal, net of salvage	(9)	(4)
Change in construction payables, net	(14)	(7)
Other investing activities	(3)	(5)
Net cash used for investing activities	(123)	(84)
Financing Activities:
Increase (decrease) in notes payable, net	(190)	46
Proceeds —
Senior notes	300	0
Capital contributions from parent company	5	5
Common stock	175	0
Redemptions and repurchases —
Preference stock	(150)	0
Redemptions — Senior notes	(85)	(125)
Payment of common stock dividends	(63)	(60)
Other financing activities	(4)	(6)
Net cash provided from financing activities	(12)	(140)
Net Change in Cash and Cash Equivalents	(11)	(28)
Cash and Cash Equivalents at Beginning of Period	56	74
Cash and Cash Equivalents at End of Period	45	46
Cash paid (received) during the period for —
Interest	22	28
Income taxes, net	7	(3)
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	19	13
MISSISSIPPI POWER CO
Operating Activities:
Net Income	(2,073)	14
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	94	82
Deferred income taxes	(860)	(16)
Allowance for equity funds used during construction	(71)	(59)
Estimated loss on Kemper IGCC	3,120	134
Other, net	(11)	(8)
Changes in certain current assets and liabilities —
-Receivables	(15)	15
-Fossil fuel stock	21	6
-Other current assets	(10)	31
-Accounts payable	(20)	(12)
-Accrued taxes	0	20
-Accrued compensation	(17)	(12)
-Over recovered regulatory clause revenues	(30)	4
-Customer liability associated with Kemper refunds	0	(69)
-Other current liabilities	7	7
Net cash provided from operating activities	135	137
Investing Activities:
Property additions	(337)	(403)
Change in construction payables, net	(19)	(11)
Government grant proceeds	0	137
Other investing activities	(5)	(19)
Net cash used for investing activities	(361)	(296)
Financing Activities:
Increase (decrease) in notes payable, net	(10)	0
Proceeds —
Capital contributions from parent company	1,001	226
Short-term borrowings	4	0
Long-term debt to parent company	40	200
Other long-term debt	0	900
Redemptions and repurchases —
Short-term borrowings	0	(475)
Long-term debt to parent company	(591)	(225)
Other long-term debt	(300)	(425)
Other financing activities	(2)	(3)
Net cash provided from financing activities	142	198
Net Change in Cash and Cash Equivalents	(84)	39
Cash and Cash Equivalents at Beginning of Period	224	98
Cash and Cash Equivalents at End of Period	140	137
Cash paid (received) during the period for —
Interest	26	26
Income taxes, net	(93)	(122)
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	59	94
SOUTHERN POWER CO
Operating Activities:
Net Income	168	152
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	264	159
Deferred income taxes	91	(71)
Amortization of investment tax credits	(28)	(15)
Deferred revenues	(34)	(31)
Income taxes receivable, non-current	(58)	0
Other, net	(1)	9
Changes in certain current assets and liabilities —
-Receivables	(58)	(76)
-Prepaid income taxes	33	(147)
-Other current assets	20	5
-Accounts payable	(45)	4
-Accrued taxes	4	62
-Other current liabilities	(8)	0
Net cash provided from operating activities	348	51
Investing Activities:
Business acquisitions, net of cash acquired	(1,020)	(502)
Property additions	(145)	(1,281)
Investment in restricted cash	(16)	(646)
Distribution of restricted cash	27	649
Change in construction payables, net	(167)	(137)
Payments pursuant to LTSAs	(68)	(43)
Other investing activities	(2)	(25)
Net cash used for investing activities	(1,391)	(1,985)
Financing Activities:
Increase (decrease) in notes payable, net	189	695
Proceeds —
Senior notes	0	1,241
Capital contributions from parent company	0	300
Redemptions and repurchases —
Distributions to noncontrolling interests	(40)	(11)
Capital contributions from noncontrolling interests	73	179
Purchase of membership interests from noncontrolling interests	0	(129)
Payment of common stock dividends	(158)	(136)
Other financing activities	(21)	(13)
Net cash provided from financing activities	43	2,126
Net Change in Cash and Cash Equivalents	(1,000)	192
Cash and Cash Equivalents at Beginning of Period	1,099	830
Cash and Cash Equivalents at End of Period	99	1,022
Cash paid (received) during the period for —
Interest	113	42
Income taxes, net	(117)	115
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	19	108
SOUTHERN Co GAS
Operating Activities:
Net Income	288
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total	244
Deferred income taxes	144
Stock based compensation expense	19
Hedge settlements	0
Mark-to-market adjustments	(49)
Other, net	(53)
Changes in certain current assets and liabilities —
-Receivables	420
-Natural gas for sale, net of temporary LIFO liquidation	223
-Prepaid income taxes	24
-Other current assets	(12)
-Accounts payable	(102)
-Accrued taxes	(8)
-Accrued compensation	(12)
-Other current liabilities	25
Net cash provided from operating activities	1,151
Investing Activities:
Property additions	(684)
Cost of removal, net of salvage	(25)
Change in construction payables, net	23
Investment in unconsolidated subsidiaries	(111)
Other investing activities	16
Net cash used for investing activities	(781)
Financing Activities:
Increase (decrease) in notes payable, net	(631)
Redemptions and repurchases — First mortgage bonds	0
Proceeds —
First mortgage bonds	0
Senior notes	450
Capital contributions from parent company	57
Redemptions and repurchases —
Distributions to noncontrolling interests	0
Payment of common stock dividends	(221)
Other financing activities	(6)
Net cash provided from financing activities	(351)
Net Change in Cash and Cash Equivalents	19
Cash and Cash Equivalents at Beginning of Period	19
Cash and Cash Equivalents at End of Period	38
Cash paid (received) during the period for —
Interest	105
Income taxes, net	20
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period	$ 84
Predecessor | SOUTHERN Co GAS
Operating Activities:
Net Income		145
Adjustments to reconcile consolidated net income (loss) to net cash provided from operating activities —
Depreciation and amortization, total		206
Deferred income taxes		8
Stock based compensation expense		20
Hedge settlements		(26)
Mark-to-market adjustments		162
Other, net		(77)
Changes in certain current assets and liabilities —
-Receivables		181
-Natural gas for sale, net of temporary LIFO liquidation		273
-Prepaid income taxes		151
-Other current assets		37
-Accounts payable		43
-Accrued taxes		41
-Accrued compensation		(21)
-Other current liabilities		(30)
Net cash provided from operating activities		1,113
Investing Activities:
Property additions		(509)
Cost of removal, net of salvage		(32)
Change in construction payables, net		(7)
Investment in unconsolidated subsidiaries		(14)
Other investing activities		3
Net cash used for investing activities		(559)
Financing Activities:
Increase (decrease) in notes payable, net		(896)
Redemptions and repurchases — First mortgage bonds		(125)
Proceeds —
First mortgage bonds		250
Senior notes		350
Capital contributions from parent company		0
Redemptions and repurchases —
Distributions to noncontrolling interests		(19)
Payment of common stock dividends		(128)
Other financing activities		10
Net cash provided from financing activities		(558)
Net Change in Cash and Cash Equivalents		(4)
Cash and Cash Equivalents at Beginning of Period		19
Cash and Cash Equivalents at End of Period		15
Cash paid (received) during the period for —
Interest		119
Income taxes, net		(100)
Noncash Investing and Financing Items [Abstract]
Noncash transactions — Accrued property additions at end of period		$ 41

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Net cash paid for capitalized interest	$ 55	$ 61
ALABAMA POWER CO
Net cash paid for capitalized interest	6	7
GEORGIA POWER CO
Net cash paid for capitalized interest	11	10
GULF POWER CO
Net cash paid for capitalized interest	0	0
MISSISSIPPI POWER CO
Interest paid	53	49
Net cash paid for capitalized interest	27	23
SOUTHERN POWER CO
Net cash paid for capitalized interest	4	21
SOUTHERN Co GAS
Net cash paid for capitalized interest	$ 7
Predecessor | SOUTHERN Co GAS
Net cash paid for capitalized interest		$ 3

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 1,433	$ 1,975
Receivables —
Customer accounts receivable	1,600	1,565
Energy marketing receivables	482	623
Unbilled revenues	593	706
Under recovered regulatory clause revenues	26	18
Income taxes receivable, current	544	544
Other accounts and notes receivable	513	377
Accumulated provision for uncollectible accounts	(52)	(43)
Materials and supplies	1,461	1,462
Fossil fuel for generation	624	689
Natural gas for sale	477	631
Prepaid expenses	361	364
Other regulatory assets, current	569	581
Other current assets	206	230
Total current assets	8,837	9,722
Property, Plant, and Equipment:
In service	101,021	98,416
Less: Accumulated depreciation	30,667	29,852
Plant in service, net of depreciation	70,354	68,564
Nuclear fuel, at amortized cost	892	905
Construction work in progress	7,440	8,977
Total property, plant, and equipment	78,686	78,446
Other Property and Investments:
Goodwill	6,271	6,251
Equity investments in unconsolidated subsidiaries	1,632	1,549
Other intangible assets, net of amortization	929	970
Nuclear decommissioning trusts, at fair value	1,722	1,606
Leveraged leases	782	774
Miscellaneous property and investments	230	270
Total other property and investments	11,566	11,420
Deferred Charges and Other Assets:
Deferred charges related to income taxes	1,325	1,629
Unamortized loss on reacquired debt	215	223
Other regulatory assets, deferred	6,668	6,851
Other deferred charges and assets	1,387	1,406
Total deferred charges and other assets	9,595	10,109
Total Assets	108,684	109,697
Current Liabilities:
Securities due within one year	3,031	2,587
Notes payable	3,274	2,241
Energy marketing trade payables	534	597
Accounts payable —
Accounts payable	1,920	2,228
Customer deposits	546	558
Accrued taxes —
Accrued income taxes	125	193
Unrecognized tax benefits	400	385
Other accrued taxes	490	667
Accrued interest	508	518
Accrued compensation	584	915
Asset retirement obligations, current	300	378
Liabilities from risk management activities, net of collateral	71	107
Acquisitions payable	0	489
Other regulatory liabilities, current	169	236
Other current liabilities	799	818
Total current liabilities	12,751	12,917
Long-term Debt	43,885	42,629
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	13,529	14,092
Deferred credits related to income taxes	212	219
Accumulated deferred ITCs	2,301	2,228
Employee benefit obligations	2,156	2,299
Asset retirement obligations, deferred	4,297	4,136
Accrued environmental remediation	399	397
Other cost of removal obligations	2,706	2,748
Other regulatory liabilities, deferred	233	258
Other deferred credits and liabilities	805	880
Total deferred credits and other liabilities	26,638	27,257
Total Liabilities	83,274	82,803
Redeemable Preferred Stock of Subsidiaries	118	118
Redeemable Noncontrolling Interests	51	164
Common Stockholders' Equity:
Par value	4,997	4,952
Paid-in capital	10,106	9,661
Treasury, at cost	(34)	(31)
Retained earnings (accumulated deficit)	8,494	10,356
Accumulated other comprehensive loss	(191)	(180)
Total Common Stockholders' Equity	23,372	24,758
Preferred and Preference Stock of Subsidiaries	462	609
Noncontrolling Interests	1,407	1,245
Total Stockholders' Equity	25,241	26,612
Total Liabilities and Stockholders' Equity	108,684	109,697
ALABAMA POWER CO
Current Assets:
Cash and cash equivalents	639	420
Receivables —
Customer accounts receivable	357	348
Unbilled revenues	161	146
Other accounts and notes receivable	36	27
Affiliated	33	40
Accumulated provision for uncollectible accounts	(9)	(10)
Materials and supplies	443	435
Fossil fuel for generation	191	205
Prepaid expenses	86	34
Other regulatory assets, current	135	149
Other current assets	7	11
Total current assets	2,079	1,805
Property, Plant, and Equipment:
In service	26,466	26,031
Less: Accumulated depreciation	9,354	9,112
Plant in service, net of depreciation	17,112	16,919
Nuclear fuel, at amortized cost	333	336
Construction work in progress	668	491
Total property, plant, and equipment	18,113	17,746
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	67	66
Nuclear decommissioning trusts, at fair value	848	792
Miscellaneous property and investments	119	112
Total other property and investments	1,034	970
Deferred Charges and Other Assets:
Deferred charges related to income taxes	526	525
Deferred under recovered regulatory clause revenues	6	150
Other regulatory assets, deferred	1,209	1,157
Other deferred charges and assets	166	163
Total deferred charges and other assets	1,907	1,995
Total Assets	23,133	22,516
Current Liabilities:
Securities due within one year	361	561
Accounts payable —
Affiliated	242	297
Other	317	433
Customer deposits	91	88
Accrued taxes —
Accrued income taxes	39	45
Other accrued taxes	97	42
Accrued interest	81	78
Accrued compensation	125	193
Other regulatory liabilities, current	15	85
Other current liabilities	63	76
Total current liabilities	1,431	1,898
Long-term Debt	7,082	6,535
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	4,842	4,654
Deferred credits related to income taxes	64	65
Accumulated deferred ITCs	113	110
Employee benefit obligations	269	300
Asset retirement obligations, deferred	1,543	1,503
Other cost of removal obligations	648	684
Other regulatory liabilities, deferred	84	100
Other deferred credits and liabilities	69	63
Total deferred credits and other liabilities	7,632	7,479
Total Liabilities	16,145	15,912
Redeemable Preferred Stock	85	85
Preference Stock	196	196
Common Stockholders' Equity:
Par value	1,222	1,222
Paid-in capital	2,950	2,613
Retained earnings (accumulated deficit)	2,564	2,518
Accumulated other comprehensive loss	(29)	(30)
Total Common Stockholders' Equity	6,707	6,323
Total Liabilities and Stockholders' Equity	23,133	22,516
GEORGIA POWER CO
Current Assets:
Cash and cash equivalents	91	3
Receivables —
Customer accounts receivable	565	523
Unbilled revenues	251	224
Joint owner accounts receivable	199	57
Other accounts and notes receivable	62	81
Affiliated	22	18
Accumulated provision for uncollectible accounts	(3)	(3)
Materials and supplies	477	479
Fossil fuel for generation	330	298
Prepaid expenses	55	105
Other regulatory assets, current	193	193
Other current assets	22	38
Total current assets	2,264	2,016
Property, Plant, and Equipment:
In service	34,410	33,841
Less: Accumulated depreciation	11,502	11,317
Plant in service, net of depreciation	22,908	22,524
Nuclear fuel, at amortized cost	559	569
Construction work in progress	5,422	4,939
Total property, plant, and equipment	28,889	28,032
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	56	60
Nuclear decommissioning trusts, at fair value	874	814
Miscellaneous property and investments	51	46
Total other property and investments	981	920
Deferred Charges and Other Assets:
Deferred charges related to income taxes	675	676
Other regulatory assets, deferred	2,790	2,774
Other deferred charges and assets	589	417
Total deferred charges and other assets	4,054	3,867
Total Assets	36,188	34,835
Current Liabilities:
Securities due within one year	261	460
Notes payable	1,228	391
Accounts payable —
Affiliated	367	438
Other	657	589
Customer deposits	269	265
Accrued taxes —
Accrued income taxes	212	407
Accrued interest	115	106
Accrued compensation	141	224
Asset retirement obligations, current	251	299
Other current liabilities	185	297
Total current liabilities	3,686	3,476
Long-term Debt	10,793	10,225
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	6,163	6,000
Deferred credits related to income taxes	118	121
Accumulated deferred ITCs	251	256
Employee benefit obligations	652	703
Asset retirement obligations, deferred	2,340	2,233
Other deferred credits and liabilities	206	199
Total deferred credits and other liabilities	9,730	9,512
Total Liabilities	24,209	23,213
Redeemable Preferred Stock	45	45
Preference Stock	221	221
Common Stockholders' Equity:
Par value	398	398
Paid-in capital	7,274	6,885
Retained earnings (accumulated deficit)	4,052	4,086
Accumulated other comprehensive loss	(11)	(13)
Total Common Stockholders' Equity	11,713	11,356
Total Liabilities and Stockholders' Equity	36,188	34,835
GULF POWER CO
Current Assets:
Cash and cash equivalents	45	56
Receivables —
Customer accounts receivable	77	72
Unbilled revenues	70	55
Under recovered regulatory clause revenues	26	17
Other accounts and notes receivable	11	6
Affiliated	8	17
Accumulated provision for uncollectible accounts	(1)	(1)
Materials and supplies	57	55
Fossil fuel for generation	67	71
Other regulatory assets, current	55	44
Other current assets	17	30
Total current assets	432	422
Property, Plant, and Equipment:
In service	5,156	5,140
Less: Accumulated depreciation	1,427	1,382
Plant in service, net of depreciation	3,729	3,758
Construction work in progress	59	51
Total property, plant, and equipment	3,788	3,809
Deferred Charges and Other Assets:
Deferred charges related to income taxes	57	58
Other regulatory assets, deferred	510	512
Other deferred charges and assets	22	21
Total deferred charges and other assets	589	591
Total Assets	4,809	4,822
Current Liabilities:
Securities due within one year	27	87
Notes payable	78	268
Accounts payable —
Affiliated	52	59
Other	46	54
Customer deposits	35	35
Accrued taxes —
Other accrued taxes	27	20
Accrued interest	9	8
Accrued compensation	23	40
Deferred capacity expense, current	22	22
Other regulatory liabilities, current	0	16
Other current liabilities	43	40
Total current liabilities	362	649
Long-term Debt	1,265	987
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	966	948
Employee benefit obligations	92	96
Deferred capacity expense	108	119
Asset retirement obligations, deferred	125	120
Other cost of removal obligations	218	249
Other regulatory liabilities, deferred	46	47
Other deferred credits and liabilities	74	71
Total deferred credits and other liabilities	1,629	1,650
Total Liabilities	3,256	3,286
Preference Stock	0	147
Common Stockholders' Equity:
Par value	678	503
Paid-in capital	596	589
Retained earnings (accumulated deficit)	280	296
Accumulated other comprehensive loss	(1)	1
Total Common Stockholders' Equity	1,553	1,389
Total Liabilities and Stockholders' Equity	4,809	4,822
MISSISSIPPI POWER CO
Current Assets:
Cash and cash equivalents	140	224
Receivables —
Customer accounts receivable	33	29
Unbilled revenues	42	42
Income taxes receivable, current	544	544
Other accounts and notes receivable	25	14
Affiliated	20	15
Materials and supplies	44	76
Fossil fuel for generation	20	100
Other regulatory assets, current	114	115
Other current assets	2	8
Total current assets	984	1,167
Property, Plant, and Equipment:
In service	4,826	4,865
Less: Accumulated depreciation	1,283	1,289
Plant in service, net of depreciation	3,543	3,576
Construction work in progress	56	2,545
Total property, plant, and equipment	3,599	6,121
Other Property and Investments:
Total other property and investments	22	12
Deferred Charges and Other Assets:
Deferred charges related to income taxes	61	361
Other regulatory assets, deferred	441	518
Accumulated deferred income taxes	404	0
Other deferred charges and assets	20	56
Total deferred charges and other assets	926	935
Total Assets	5,531	8,235
Current Liabilities:
Securities due within one year - parent	0	551
Securities due within one year	1,028	78
Notes payable	17	23
Accounts payable —
Affiliated	54	62
Other	109	135
Customer deposits	16	16
Accrued taxes —
Unrecognized tax benefits	385	383
Other accrued taxes	97	99
Accrued interest	52	46
Accrued compensation	25	42
Asset retirement obligations, current	21	32
Over recovered regulatory clause liabilities	21	51
Other current liabilities	89	20
Total current liabilities	1,914	1,538
Long-term Debt	1,169	2,424
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	0	756
Employee benefit obligations	111	115
Asset retirement obligations, deferred	149	146
Other cost of removal obligations	173	170
Other regulatory liabilities, deferred	80	84
Other deferred credits and liabilities	29	26
Total deferred credits and other liabilities	542	1,297
Total Liabilities	3,625	5,259
Redeemable Preferred Stock	33	33
Common Stockholders' Equity:
Par value	38	38
Paid-in capital	4,527	3,525
Retained earnings (accumulated deficit)	(2,689)	(616)
Accumulated other comprehensive loss	(3)	(4)
Total Common Stockholders' Equity	1,873	2,943
Total Liabilities and Stockholders' Equity	5,531	8,235
SOUTHERN POWER CO
Current Assets:
Cash and cash equivalents	99	1,099
Receivables —
Customer accounts receivable	158	102
Other accounts and notes receivable	37	34
Affiliated	65	57
Materials and supplies	349	337
Fossil fuel for generation	15	15
Prepaid income taxes	41	74
Other current assets	26	39
Total current assets	790	1,757
Property, Plant, and Equipment:
In service	13,731	12,728
Less: Accumulated depreciation	1,689	1,484
Plant in service, net of depreciation	12,042	11,244
Construction work in progress	344	398
Total property, plant, and equipment	12,386	11,642
Other Property and Investments:
Goodwill	2	2
Intangible assets, net (including goodwill)	423	436
Total other property and investments	423	436
Deferred Charges and Other Assets:
Prepaid LTSAs	61	101
Accumulated deferred income taxes	536	594
Income Taxes Receivable, Noncurrent	69	11
Other deferred charges and assets — affiliated	28	13
Other deferred charges and assets	410	615
Total deferred charges and other assets	1,104	1,334
Total Assets	14,703	15,169
Current Liabilities:
Securities due within one year	909	560
Notes payable	398	209
Accounts payable —
Affiliated	68	88
Other	93	278
Accrued taxes —
Accrued income taxes	35	148
Other accrued taxes	21	7
Accrued interest	25	36
Acquisitions payable	0	461
Contingent consideration	11	46
Other current liabilities	67	70
Total current liabilities	1,627	1,903
Long-term Debt	4,816	5,068
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	174	152
Accumulated deferred ITCs	1,914	1,839
Asset retirement obligations, deferred	69	64
Other deferred credits and liabilities	238	304
Total deferred credits and other liabilities	2,395	2,359
Total Liabilities	8,838	9,330
Redeemable Noncontrolling Interests	51	164
Common Stockholders' Equity:
Par value	0	0
Paid-in capital	3,671	3,671
Retained earnings (accumulated deficit)	717	724
Accumulated other comprehensive loss	19	35
Total Common Stockholders' Equity	4,407	4,430
Noncontrolling interests	1,407	1,245
Total Stockholders' Equity	5,814	5,675
Total Liabilities and Stockholders' Equity	14,703	15,169
SOUTHERN Co GAS
Current Assets:
Cash and cash equivalents	38	19
Receivables —
Customer accounts receivable	270	364
Energy marketing receivables	482	623
Unbilled revenues	69	239
Other accounts and notes receivable	63	76
Accumulated provision for uncollectible accounts	(35)	(27)
Materials and supplies	24	26
Natural gas for sale	477	631
Prepaid expenses	69	80
Assets from risk management activities, net of collateral	114	128
Other regulatory assets, current	72	81
Other current assets	20	10
Total current assets	1,663	2,250
Property, Plant, and Equipment:
In service	14,850	14,508
Less: Accumulated depreciation	4,550	4,439
Plant in service, net of depreciation	10,300	10,069
Construction work in progress	779	496
Total property, plant, and equipment	11,079	10,565
Other Property and Investments:
Goodwill	5,967	5,967
Equity investments in unconsolidated subsidiaries	1,610	1,541
Other intangible assets, net of amortization	320	366
Miscellaneous property and investments	21	21
Total other property and investments	7,918	7,895
Deferred Charges and Other Assets:
Other regulatory assets, deferred	963	973
Other deferred charges and assets	186	170
Total deferred charges and other assets	1,149	1,143
Total Assets	21,809	21,853
Current Liabilities:
Securities due within one year	22	22
Notes payable	626	1,257
Energy marketing trade payables	534	597
Accounts payable —
Accounts payable	327	348
Customer deposits	134	153
Accrued taxes —
Accrued income taxes	23	26
Other accrued taxes	63	68
Accrued interest	50	48
Accrued compensation	45	58
Liabilities from risk management activities, net of collateral	20	62
Other regulatory liabilities, current	146	102
Accrued environmental remediation, current	63	69
Temporary LIFO liquidation	69	0
Other current liabilities	113	108
Total current liabilities	2,235	2,918
Long-term Debt	5,677	5,259
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	2,091	1,975
Employee benefit obligations	432	441
Accrued environmental remediation	353	357
Other cost of removal obligations	1,638	1,616
Other regulatory liabilities, deferred	50	51
Other deferred credits and liabilities	91	127
Total deferred credits and other liabilities	4,655	4,567
Total Liabilities	12,567	12,744
Common Stockholders' Equity:
Par value	0	0
Paid-in capital	9,164	9,095
Retained earnings (accumulated deficit)	55	(12)
Accumulated other comprehensive loss	23	26
Total Stockholders' Equity	9,242	9,109
Total Liabilities and Stockholders' Equity	$ 21,809	$ 21,853

Condensed Consolidated Balance9

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Other intangible assets, accumulated amortization	$ 126,000,000	$ 62,000,000
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	1,500,000,000	1,500,000,000
Common stock, shares issued (in shares)	1,000,000,000	991,000,000
Treasury shares at cost (in shares)	900,000	800,000
ALABAMA POWER CO
Common stock, par value (in dollars per share)	$ 40	$ 40
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares outstanding (in shares)	30,537,500	30,537,500
GEORGIA POWER CO
Common Stock, No Par Value	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares outstanding (in shares)	9,261,500	9,261,500
GULF POWER CO
Common Stock, No Par Value	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares outstanding (in shares)	7,392,717	5,642,717
MISSISSIPPI POWER CO
Common stock, shares authorized (in shares)	1,130,000	1,130,000
Common stock, shares outstanding (in shares)	1,121,000	1,121,000
SOUTHERN POWER CO
Other intangible assets, accumulated amortization	$ 35,000,000	$ 22,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, shares outstanding (in shares)	1,000	1,000
SOUTHERN Co GAS
Other intangible assets, accumulated amortization	$ 80,000,000	$ 34,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares outstanding (in shares)	100	100

Introduction

Introduction	6 Months Ended
	Jun. 30, 2017
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, 2016 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 June 30, 2017 and 2016 . 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. Southern Company's financial statements reflect its investments in its subsidiaries, including Southern Company Gas as a result of the Merger, on a consolidated basis. Southern Company Gas' results of operations and cash flows for the three and six months ended June 30, 2017 and financial condition as of June 30, 2017 and December 31, 2016 are reflected within Southern Company's consolidated amounts in these accompanying notes herein. The equity method is used for entities in which Southern Company has significant influence but does not control, including Southern Company Gas' investment in SNG, and for variable interest entities where Southern Company has an equity investment but is not the primary beneficiary. See Note (I) under " Southern Company – Merger with Southern Company Gas " for additional information regarding the Merger. Pursuant to the Merger, Southern Company pushed down the application of the acquisition method of accounting to the consolidated financial statements of Southern Company Gas such that the assets and liabilities are recorded at their respective fair values, and goodwill has been established for the excess of the purchase price over the fair value of net identifiable assets. Accordingly, the consolidated financial statements of Southern Company Gas for periods before and after July 1, 2016 (acquisition date) reflect different bases of accounting, and the financial positions and results of operations of those periods are not comparable. Throughout Southern Company Gas' condensed consolidated financial statements and the accompanying notes herein, periods prior to July 1, 2016 are identified as "predecessor," while periods after the acquisition date are identified as "successor." 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 Issued Accounting Standards In 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (ASC 606), replacing the existing accounting standard and industry specific guidance for revenue recognition with a five-step model for recognizing and measuring revenue from contracts with customers. The underlying principle of the standard is to recognize revenue to depict the transfer of goods or services to customers at the amount expected to be collected. The new standard also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and the related cash flows arising from contracts with customers. While the registrants expect most of their revenue to be included in the scope of ASC 606, they have not fully completed the evaluation of all revenue arrangements. The majority of Southern Company's, the traditional electric operating companies', and Southern Company Gas' revenue, including energy provided to customers, is from tariff offerings that provide electricity or natural gas without a defined contractual term, as well as longer-term contractual commitments , including PPAs and non-derivative natural gas asset management and optimization arrangements . The majority of Southern Power's revenues includes longer-term PPAs for generation capacity and energy. The registrants expect the adoption of ASC 606 will not result in a significant shift from the current timing of revenue recognition for such transactions . The registrants' ongoing evaluation of other revenue streams and related contracts includes unregulated sales to customers. Some revenue arrangements, such as certain PPAs , energy-related derivatives , and alternative revenue programs, are excluded from the scope of ASC 606 and, therefore, will be accounted for and disclosed or presented separately from revenues under ASC 606 on the registrants' financial statements. In addition, the power and utilities industry continues to evaluate other specific industry issues, including the applicability of ASC 606 to contributions in aid of construction (CIAC). Although final implementation guidance has not been issued, Southern Company, the traditional electric operating companies, and Southern Company Gas expect CIAC to be out of the scope of ASC 606. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017. The registrants intend to use the modified retrospective method of adoption effective January 1, 2018. The registrants have also elected to utilize practical expedients which allow them to apply the standard to open contracts at the date of adoption and to reflect the aggregate effect of all modifications when identifying performance obligations and allocating the transaction price for contracts modified before the effective date. Under the modified retrospective method of adoption, prior year reported results are not restated; however, a cumulative-effect adjustment to retained earnings at January 1, 2018 is recorded. In addition, disclosures will include comparative information on 2018 financial statement line items under current guidance. While the adoption of ASC 606, including the cumulative-effect adjustment, is not expected to have a material impact on either the timing or amount of revenues recognized in the registrants' financial statements, the registrants will continue to evaluate the requirements, as well as any additional clarifying guidance that may be issued. On January 26, 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to compare the implied fair value of goodwill with the carrying amount as part of Step 2 of the goodwill impairment test. Under the new standard, the goodwill impairment loss will be measured as the excess of a reporting unit's carrying amount over its fair value, not exceeding the total amount of goodwill allocated to that reporting unit, which may increase the frequency of goodwill impairment charges if a future goodwill impairment test does not pass the Step 1 evaluation. ASU 2017-04 is effective prospectively for annual and interim periods beginning on or after December 15, 2019, and early adoption is permitted on testing dates after January 1, 2017. On March 10, 2017, the FASB issued ASU No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (ASU 2017-07). ASU 2017-07 requires that an employer report the service cost component in the same line item or items as other compensation costs and requires the other components of net periodic pension and postretirement benefit costs to be separately presented in the income statement outside income from operations. Additionally, only the service cost component is eligible for capitalization, when applicable. However, all cost components remain eligible for capitalization under FERC regulations. ASU 2017-07 will be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension and postretirement benefit costs in the income statement. The capitalization of the service cost component of net periodic pension and postretirement benefit costs in assets will be applied on a prospective basis. ASU 2017-07 is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Southern Company, the traditional electric operating companies, and Southern Company Gas are currently evaluating the new standard. The presentation changes required for net periodic pension and postretirement benefit costs will result in a decrease in Southern Company's , the traditional electric operating companies', and Southern Company Gas' operating income and an increase in other income for 2016 and 2017 and are expected to result in a decrease in operating income and an increase in other income for 2018. The adoption of ASU 2017-07 is not expected to have a material impact on Southern Company's , the traditional electric operating companies', or Southern Company Gas' financial statements. Affiliate Transactions Prior to the completion of Southern Company Gas' acquisition of its 50% equity interest in SNG, SCS (as agent for Alabama Power, Georgia Power, and Southern Power) and Southern Company Gas had entered into long-term interstate natural gas transportation agreements with SNG. The interstate transportation service provided to Alabama Power, Georgia Power, Southern Power, and Southern Company Gas by SNG pursuant to these agreements is governed by the terms and conditions of SNG's natural gas tariff and is subject to FERC regulation. For the six months ended June 30, 2017 , transportation costs under these agreements for Alabama Power, Georgia Power, Southern Power, and Southern Company Gas were approximately $4 million , $51 million , $13 million , and $16 million , respectively. SCS, as agent for Georgia Power and Southern Power, has agreements with certain subsidiaries of Southern Company Gas to purchase natural gas. For the six months ended June 30, 2017 , natural gas purchases made by Georgia Power and Southern Power from Southern Company Gas' subsidiaries were approximately $9 million and $56 million , respectively. Goodwill and Other Intangible Assets At June 30, 2017 and December 31, 2016, goodwill was as follows: Goodwill At June 30, 2017 At December 31, 2016 (in millions) Southern Company $ 6,271 $ 6,251 Southern Power $ 2 $ 2 Southern Company Gas Gas distribution operations $ 4,702 $ 4,702 Gas marketing services 1,265 1,265 Southern Company Gas total $ 5,967 $ 5,967 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. Other intangible assets were as follows: At June 30, 2017 At December 31, 2016 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 $ 288 $ (57 ) $ 231 $ 268 $ (32 ) $ 236 Trade names 159 (11 ) 148 158 (5 ) 153 Patents 4 — 4 4 — 4 Backlog 5 (1 ) 4 5 (1 ) 4 Storage and transportation contracts 64 (21 ) 43 64 (2 ) 62 Software and other 4 (1 ) 3 2 — 2 PPA fair value adjustments 456 (35 ) 421 456 (22 ) 434 Total other intangible assets subject to amortization $ 980 $ (126 ) $ 854 $ 957 $ (62 ) $ 895 Other intangible assets not subject to amortization: Federal Communications Commission licenses $ 75 $ — $ 75 $ 75 $ — $ 75 Total other intangible assets $ 1,055 $ (126 ) $ 929 $ 1,032 $ (62 ) $ 970 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 456 $ (35 ) $ 421 $ 456 $ (22 ) $ 434 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 221 $ (53 ) $ 168 $ 221 $ (30 ) $ 191 Trade names 115 (6 ) 109 115 (2 ) 113 Wholesale gas services Storage and transportation contracts 64 (21 ) 43 64 (2 ) 62 Total other intangible assets subject to amortization $ 400 $ (80 ) $ 320 $ 400 $ (34 ) $ 366 Amortization associated with other intangible assets was as follows: Three Months Ended Six Months Ended June 30, 2017 (in millions) Southern Company $ 29 $ 65 Southern Power $ 6 $ 13 Southern Company Gas $ 20 $ 46 See Note 12 to the financial statements of Southern Company under "Southern Power" and Note 2 to the financial statements of Southern Power in Item 8 of the Form 10-K for additional information regarding Southern Power's PPA fair value adjustments related to its business acquisitions. Also see Note (I) under " Southern Company – Acquisition of PowerSecure " and " – Merger with Southern Company Gas " for additional information. Property Damage Reserve See Note 1 to the financial statements of Gulf Power under "Property Damage Reserve" in Item 8 of the Form 10-K for additional information. Gulf Power's cost of repairing damages from major storms and other uninsured property damages, including uninsured damages to transmission and distribution facilities, generation facilities, and other property is charged to Gulf Power's property damage reserve. In accordance with a settlement agreement approved by the Florida PSC on April 4, 2017 (2017 Rate Case Settlement Agreement), Gulf Power suspended further property damage reserve accruals effective April 2017. Gulf Power may make discretionary accruals, but is required to resume accruals of $3.5 million annually if the reserve balance falls below zero . In addition, Gulf Power may initiate a storm surcharge to recover costs associated with any tropical systems named by the National Hurricane Center or other catastrophic storm events that reduce the property damage reserve in the aggregate by approximately $31 million ( 75% of the April 1, 2017 balance) or more. The storm surcharge would begin, on an interim basis, 60 days following the filing of a cost recovery petition, would be limited to $4.00 /month for a 1,000 KWH residential customer unless Gulf Power incurs in excess of $100 million in qualified storm recovery costs in a calendar year, and would replenish the storm reserve to approximately $40 million . See Note (B) under " Regulatory Matters – Gulf Power – Retail Base Rate Cases " for additional details regarding the 2017 Rate Case Settlement Agreement. Natural Gas for Sale Southern Company Gas' natural gas distribution utilities, with the exception of Nicor Gas, carry natural gas inventory on a WACOG basis. Nicor Gas' natural gas inventory is carried at cost on a LIFO basis. Inventory decrements occurring during the year that are restored prior to year end are charged to cost of natural gas at the estimated annual replacement cost. Inventory decrements that are not restored prior to year end are charged to cost of natural gas at the actual LIFO cost of the inventory layers liquidated. Southern Company Gas' inventory decrement at June 30, 2017 is expected to be restored prior to year end. The cost of natural gas, including inventory costs, is recovered from customers under a purchased gas recovery mechanism adjusted for differences between actual costs and amounts billed; therefore, LIFO liquidations have no impact on Southern Company's or Southern Company Gas' net income. Natural gas inventories for Southern Company Gas' non-utility businesses are carried at the lower of weighted average cost or current market price, with cost determined on a WACOG basis. For any declines in market prices below the WACOG considered to be other than temporary, an adjustment is recorded to reduce the value of natural gas inventories to market value. Southern Company Gas had no material LOCOM adjustment in any period presented.

Contingencies and Regulatory Ma

Contingencies and Regulatory Matters	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
CONTINGENCIES AND REGULATORY MATTERS	CONTINGENCIES AND REGULATORY MATTERS See Note 3 to the financial statements of the registrants in Item 8 of the Form 10-K for information relating to various lawsuits, other contingencies, and regulatory matters. 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 regulation of air emissions and water discharges. Litigation over environmental issues and claims of various types, including property damage, personal injury, common law nuisance, and citizen enforcement of environmental requirements such as air quality and water standards, 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 predicted 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 On January 20, 2017, a purported 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, Atlanta Division, 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 IGCC 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. On June 12, 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. On July 27, 2017, the defendants filed a motion to dismiss the plaintiffs' amended complaint with prejudice. On February 27, 2017, Jean Vineyard filed a shareholder derivative lawsuit in the U.S. District Court for the Northern District of 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 defendants caused Southern Company to make false or misleading statements regarding the Kemper IGCC cost and schedule. Further, the complaint alleges that the defendants were unjustly enriched and caused the waste of corporate assets. The plaintiff seeks to recover, on behalf of Southern Company, unspecified actual damages and, on her own behalf, attorneys' fees and costs in bringing the lawsuit. The plaintiff also seeks certain changes to Southern Company's corporate governance and internal processes. On March 27, 2017, the court deferred this lawsuit until 30 days after certain further action in the purported securities class action complaint discussed above. On May 15, 2017, Helen E. Piper Survivor's Trust filed a shareholder derivative lawsuit in the Superior Court of Gwinnett County, State of 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 IGCC. The complaint further alleges that the individual defendants authorized or failed to correct false and misleading statements regarding the Kemper IGCC 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. On June 1, 2017, Judy Mesirov filed a shareholder derivative lawsuit in the U.S. District Court for the Northern District of Georgia, that names as defendants Southern Company, certain of its current and former 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 IGCC. The complaint further alleges that the individual defendants authorized or failed to correct false and misleading statements regarding the Kemper IGCC 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, disgorgement of profits, and equitable relief and, on her own 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. Southern Company believes these legal challenges have no merit; however, an adverse outcome in any of these proceedings could have an impact on Southern Company's results of operations, financial condition, and liquidity. Southern Company will vigorously defend itself in these matters, the ultimate outcome of which 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 municipal franchise fees (all of which are remitted to municipalities) exceeded the amounts allowed in orders of the Georgia PSC and alleging certain state tort law claims. In November 2016, the Georgia Court of Appeals reversed the trial court's previous dismissal of the case and remanded the case to the trial court for further proceedings. Georgia Power has filed a petition for writ of certiorari with the Georgia Supreme Court. Georgia Power believes the plaintiffs' claims have no merit and intends to vigorously defend itself in this matter. The ultimate outcome of this matter cannot be determined at this time. Southern Power During 2015, Southern Power indirectly acquired a 51% membership interest in RE Roserock LLC (Roserock), the owner of the Roserock facility in Pecos County, Texas, which was under construction by Recurrent Energy, LLC and was subsequently placed in service in November 2016. Prior to placing the facility in service, certain solar panels were damaged during installation. While the facility currently is generating energy consistent with operational expectations and PPA obligations, Southern Power is pursuing remedies under its insurance policies and other contracts to repair or replace these solar panels. In connection therewith, Southern Power is withholding payments of approximately $26 million from the construction contractor, who has placed a lien on the Roserock facility for the same amount. The amounts withheld are included in other accounts and notes payable and other current liabilities on Southern Company's consolidated balance sheets and other accounts payable and other current liabilities on Southern Power's consolidated balance sheets. On May 18, 2017, Roserock filed a lawsuit in the state district court in Pecos County, Texas, against X.L. America, Inc. (XL) and North American Elite Insurance Company (North American Elite) seeking recovery from an insurance policy for damages resulting from a hail storm and certain installation practices by the construction contractor, McCarthy Building Companies, Inc. (McCarthy). On May 19, 2017, Roserock filed a separate lawsuit against McCarthy in the state district court in Travis County, Texas alleging breach of contract and breach of warranty for the damages sustained at the Roserock facility, which has since been moved to the U.S. District Court for the Western District of Texas. On May 22, 2017, McCarthy filed a lawsuit against Roserock, Array Technologies, Inc., Canadian Solar (USA), Inc., XL, and North American Elite in the U.S. District Court for the Western District of Texas alleging, among other things, breach of contract, and requesting foreclosure of mechanic's liens against Roserock. On July 18, 2017, the U.S. District Court for the Western District of Texas consolidated the two pending lawsuits. Southern Power intends to vigorously pursue and defend these matters, the ultimate outcome of which cannot be determined at this time. Southern Company Gas Nicor Gas and Nicor Energy Services Company, wholly-owned subsidiaries of Southern Company Gas, and Nicor Inc. were defendants in a putative class action initially filed in 2011 in the state court in Cook County, Illinois. The plaintiffs purported to represent a class of the customers who purchased the Gas Line Comfort Guard product from Nicor Energy Services Company and variously alleged that the marketing, sale, and billing of the Gas Line Comfort Guard product violated the Illinois Consumer Fraud and Deceptive Business Practices Act, constituting common law fraud and resulting in unjust enrichment of these entities. The plaintiffs sought, on behalf of the classes they purported to represent, actual and punitive damages, interest, costs, attorney fees, and injunctive relief. On February 8, 2017, the judge denied the plaintiffs' motion for class certification and Southern Company Gas' motion for summary judgment. On March 7, 2017, the parties reached a settlement, which was finalized and effective on April 3, 2017. The settlement did not have a material impact on Southern Company's or Southern Company Gas' financial statements. Environmental Remediation The Southern Company system must comply with environmental laws and regulations that cover 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, New Jersey, Georgia, and Florida 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 $12 million and $17 million as of June 30, 2017 and December 31, 2016, 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. Gulf Power's environmental remediation liability includes estimated costs of environmental remediation projects of approximately $51 million and $44 million as of June 30, 2017 and December 31, 2016, respectively. These estimated costs primarily relate to site closure criteria by the Florida Department of Environmental Protection (FDEP) for potential impacts to soil and groundwater from herbicide applications at Gulf Power's substations. The schedule for completion of the remediation projects is subject to FDEP approval. The projects have been approved by the Florida PSC for recovery through Gulf Power's environmental cost recovery clause; therefore, these liabilities have no impact on net income. Southern Company Gas' environmental remediation liability was $416 million and $426 million as of June 30, 2017 and December 31, 2016, 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 $5 million of the total accrued remediation costs. The final outcome of these matters cannot be determined at this time. However, the final disposition of these matters is not expected to have a material impact on the financial statements of Southern Company, Georgia Power, Gulf Power, or Southern Company Gas. FERC Matters Municipal and Rural Associations Tariff See Note 3 to the financial statements of Mississippi Power under "FERC Matters" in Item 8 of the Form 10-K for additional information regarding a settlement agreement entered into by Mississippi Power regarding the establishment of a regulatory asset for Kemper IGCC-related costs. See " Integrated Coal Gasification Combined Cycle " herein for information regarding the Kemper IGCC. In March 2016, Mississippi Power reached a settlement agreement with its wholesale customers, which was subsequently approved by the FERC, for an increase in wholesale base revenues under the MRA cost-based electric tariff, primarily as a result of placing scrubbers for Plant Daniel Units 1 and 2 in service in 2015. The settlement agreement became effective for services rendered beginning May 1, 2016, resulting in an estimated annual revenue increase of $7 million under the MRA cost-based electric tariff. Additionally, under the settlement agreement, the tariff customers agreed to similar regulatory treatment for MRA tariff ratemaking as the treatment approved for retail ratemaking through an order issued by the Mississippi PSC in December 2015 (In-Service Asset Rate Order). This regulatory treatment primarily includes (i) recovery of the Kemper IGCC assets currently operational and providing service to customers and other related costs, (ii) amortization of the Kemper IGCC-related regulatory assets included in rates under the settlement agreement over the 36 months ending April 30, 2019, (iii) Kemper IGCC-related expenses included in rates under the settlement agreement no longer being deferred and charged to expense, and (iv) removing all of the Kemper IGCC CWIP from rate base with a corresponding increase in accrual of AFUDC. The additional resulting AFUDC totaled approximately $22 million through the suspension of Kemper IGCC start-up activities. See " Integrated Coal Gasification Combined Cycle " herein for additional information. Fuel Cost Recovery Mississippi Power has a wholesale MRA and a Market Based (MB) fuel cost recovery factor. At June 30, 2017 , the amount of over-recovered wholesale MRA fuel costs included in the balance sheets was $7 million compared to $13 million at December 31, 2016 . Over-recovered wholesale MB fuel costs included in the balance sheets were immaterial at June 30, 2017 and December 31, 2016 . See Note 3 to the financial statements of Mississippi Power under "FERC Matters – Fuel Cost Recovery" in Item 8 of the Form 10-K for additional information. Market-Based Rate Authority See Note 3 to the financial statements of Southern Company and Mississippi Power under "FERC Matters – Market-Based Rate Authority" and Note 3 to the financial statements of Alabama Power, Georgia Power, Gulf Power, and Southern Power under "FERC Matters" in Item 8 of the Form 10-K for additional information regarding the traditional electric operating companies' and Southern Power's market power proceeding and amendment to their market-rate tariff. On May 17, 2017, the FERC accepted the traditional electric operating companies' and Southern Power's compliance filing accepting the terms of the FERC's February 2, 2017 order regarding an amendment by the traditional electric operating companies and Southern Power to their market-based rate tariff. While the FERC's order references the traditional electric operating companies' and Southern Power's market power proceeding, it remains a separate, ongoing matter. Regulatory Matters Alabama Power See Note 3 to the financial statements of Southern Company and Alabama Power under "Regulatory Matters – Alabama Power" and "Retail Regulatory Matters," respectively, in Item 8 of the Form 10-K for additional information regarding Alabama Power's recovery of retail costs through various regulatory clauses and accounting orders. The balance of each regulatory clause recovery on the balance sheet follows: Regulatory Clause Balance Sheet Line Item June 30, December 31, (in millions) Rate CNP Compliance (*) Deferred under recovered regulatory clause revenues $ 6 $ 9 Rate CNP PPA Over recovered regulatory clause revenues 1 — Deferred under recovered regulatory clause revenues — 142 Retail Energy Cost Recovery Other regulatory liabilities, current 11 76 Natural Disaster Reserve Other regulatory liabilities, deferred 56 69 (*) In accordance with an accounting order issued on February 17, 2017 by the Alabama PSC, Alabama Power reclassified $36 million of its under recovered balance for Rate CNP Compliance to a deferred regulatory asset account. Georgia Power Rate Plans See Note 3 to the financial statements of Southern Company and Georgia Power under "Regulatory Matters – Georgia Power – Rate Plans" and "Retail Regulatory Matters – Rate Plans," respectively, in Item 8 of the Form 10-K for additional information. Georgia Power's revenues from regulated retail operations are collected through various rate mechanisms subject to the oversight of the Georgia PSC. Georgia Power currently recovers its costs from the regulated retail business through the 2013 ARP, which includes traditional base tariff rates, Demand-Side Management tariffs, Environmental Compliance Cost Recovery tariffs, and Municipal Franchise Fee tariffs. In addition, financing costs related to the construction of Plant Vogtle Units 3 and 4 are being collected through the NCCR tariff and fuel costs are collected through a separate fuel cost recovery tariff. See " Nuclear Construction " herein and Note 3 to the financial statements of Southern Company under "Regulatory Matters – Georgia Power – Nuclear Construction" and Georgia Power under "Retail Regulatory Matters – Nuclear Construction" in Item 8 of the Form 10-K for additional information regarding the NCCR tariff. Also see " Fuel Cost Recovery " herein and Note 3 to the financial statements of Southern Company under "Regulatory Matters – Georgia Power – Fuel Cost Recovery" and Georgia Power under "Retail Regulatory Matters – Fuel Cost Recovery" in Item 8 of the Form 10-K for additional information regarding fuel cost recovery. Integrated Resource Plan See Note 3 to the financial statements of Southern Company and Georgia Power under "Regulatory Matters – Georgia Power – Integrated Resource Plan" and "Retail Regulatory Matters – Integrated Resource Plan," respectively, in Item 8 of the Form 10-K for additional information regarding Georgia Power's triennial Integrated Resource Plan. On March 7, 2017, the Georgia PSC approved Georgia Power's decision to suspend work at a future generation site in Stewart County, Georgia, due to changing economics, including load forecasts and lower fuel costs. The timing of recovery for costs incurred of approximately $50 million will be determined by the Georgia PSC in a future base rate case. The ultimate outcome of this matter cannot be determined at this time. Fuel Cost Recovery See Note 3 to the financial statements of Southern Company and Georgia Power under "Regulatory Matters – Georgia Power – Fuel Cost Recovery" and "Retail Regulatory Matters – Fuel Cost Recovery," respectively, in Item 8 of the Form 10-K for additional information. As of June 30, 2017 , Georgia Power's under recovered fuel balance totaled $61 million and is included in other deferred charges and assets on Southern Company's and Georgia Power's condensed balance sheets. As of December 31, 2016 , Georgia Power's over recovered fuel balance totaled $84 million and is included in other current liabilities on Southern Company's and Georgia Power's condensed balance sheets. Fuel cost recovery revenues are adjusted for differences in actual recoverable fuel costs and amounts billed in current regulated rates. Accordingly, changes in the billing factor will not have a significant effect on Southern Company's or Georgia Power's revenues or net income, but will affect cash flow. Nuclear Construction See Note 3 to the financial statements of Southern Company and Georgia Power under "Regulatory Matters – Georgia Power – Nuclear Construction" and "Retail Regulatory Matters – Nuclear Construction," respectively, in Item 8 of the Form 10-K for additional information regarding Georgia Power's construction of Plant Vogtle Units 3 and 4, Vogtle Construction Monitoring (VCM) reports, the NCCR tariff, and the Contractor Settlement Agreement. Vogtle 3 and 4 Agreement and EPC Contractor Bankruptcy In 2008, Georgia Power, acting for itself and as agent for the Vogtle Owners, entered into the Vogtle 3 and 4 Agreement, pursuant to which the EPC Contractor agreed to design, engineer, procure, construct, and test Plant Vogtle Units 3 and 4. Under the terms of the Vogtle 3 and 4 Agreement, the Vogtle Owners agreed to pay a purchase price subject to certain price escalations and adjustments, including fixed escalation amounts and index-based adjustments, as well as adjustments for change orders, and performance bonuses for early completion and unit performance. Georgia Power's proportionate share of Plant Vogtle Units 3 and 4 is 45.7% . The Vogtle 3 and 4 Agreement also provided for liquidated damages upon the EPC Contractor's failure to fulfill the schedule and certain performance guarantees, each subject to an aggregate cap of 10% of the contract price, or approximately $920 million (approximately $420 million based on Georgia Power's ownership interest). Under the Toshiba Guarantee, Toshiba guaranteed certain payment obligations of the EPC Contractor, including any liability of the EPC Contractor for abandonment of work. In January 2016, Westinghouse delivered to the Vogtle Owners $920 million of letters of credit from financial institutions (Westinghouse Letters of Credit) to secure a portion of the EPC Contractor's potential obligations under the Vogtle 3 and 4 Agreement. The Westinghouse Letters of Credit are subject to annual renewals through June 30, 2020 and require 60 days' written notice to Georgia Power in the event the Westinghouse Letters of Credit will not be renewed. Under the terms of the Vogtle 3 and 4 Agreement, the EPC Contractor did not have the right to terminate the Vogtle 3 and 4 Agreement for convenience. In the event of an abandonment of work by the EPC Contractor, the maximum liability of the EPC Contractor under the Vogtle 3 and 4 Agreement was 40% of the contract price (approximately $1.7 billion based on Georgia Power's ownership interest). On March 29, 2017, the EPC Contractor filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy Code. To provide for a continuation of work at Plant Vogtle Units 3 and 4, Georgia Power, acting for itself and as agent for the Vogtle Owners, entered into an interim assessment agreement with the EPC Contractor (Interim Assessment Agreement), which the bankruptcy court approved on March 30, 2017. The Interim Assessment Agreement provided, among other items, that during the term of the Interim Assessment Agreement (i) Georgia Power was obligated to pay, on behalf of the Vogtle Owners, all costs accrued by the EPC Contractor for subcontractors and vendors for services performed or goods provided, with these amounts paid to the EPC Contractor, except that amounts accrued for Fluor Corporation (Fluor) were paid directly to Fluor; (ii) the EPC Contractor provided certain engineering, procurement, and management services for Plant Vogtle Units 3 and 4, to the same extent as contemplated by the Vogtle 3 and 4 Agreement, and Georgia Power, on behalf of the Vogtle Owners, made payments of $5.4 million per week for these services; (iii) Georgia Power had the right to make payments, on behalf of the Vogtle Owners, directly to subcontractors and vendors who had accounts past due with the EPC Contractor; (iv) the EPC Contractor used commercially reasonable efforts to provide information reasonably requested by Georgia Power as was necessary to continue construction and investigation of the completion status of Plant Vogtle Units 3 and 4; (v) the EPC Contractor rejected or accepted the Vogtle 3 and 4 Agreement by the termination of the Interim Assessment Agreement; and (vi) Georgia Power did not exercise any remedies against Toshiba under the Toshiba Guarantee. Under the Interim Assessment Agreement, all parties expressly reserved all rights and remedies under the Vogtle 3 and 4 Agreement and all related security and collateral under applicable law. The Interim Assessment Agreement, as amended, expired on July 27, 2017. Georgia Power's aggregate liability for the Vogtle Owners under the Interim Assessment Agreement totaled approximately $650 million , of which $552 million had been paid or accrued as of June 30, 2017. Georgia Power's proportionate share of this aggregate liability totaled approximately $297 million . Subsequent to the EPC Contractor bankruptcy filing, a number of subcontractors to the EPC Contractor, including Fluor Enterprises, Inc., a subsidiary of Fluor, alleged non-payment by the EPC Contractor for amounts owed for work performed on Plant Vogtle Units 3 and 4. Georgia Power, acting for itself and as agent for the Vogtle Owners, has taken, and continues to take, actions to remove liens filed by these subcontractors through the posting of surety bonds. Georgia Power estimates the aggregate liability, through July 31, 2017, of the Vogtle Owners for the removal of subcontractor liens and payment of other EPC Contractor pre-petition accounts payable to total approximately $400 million , of which $354 million had been paid or accrued as of June 30, 2017. Georgia Power's proportionate share of this aggregate liability totaled approximately $183 million . On June 9, 2017, Georgia Power and the other Vogtle Owners and Toshiba entered into a settlement agreement regarding the Toshiba Guarantee (Guarantee Settlement Agreement). Pursuant to the Guarantee Settlement Agreement, Toshiba acknowledged the amount of its obligation under the Toshiba Guarantee is $3.68 billion (Guarantee Obligations), of which Georgia Power's proportionate share is approximately $1.7 billion , and that the Guarantee Obligations exist regardless of whether Plant Vogtle Units 3 and 4 are completed. The Guarantee Settlement Agreement also provides for a schedule of payments for the Guarantee Obligations, beginning in October 2017 and continuing through January 2021. In the event Toshiba receives certain payments, including sale proceeds, from or related to Westinghouse (or its subsidiaries) or Toshiba Nuclear Energy Holdings (UK) Limited (or its subsidiaries), it will hold a portion of such payments in trust for the Vogtle Owners and promptly pay them as offsets against any remaining Guarantee Obligations. Under the Guarantee Settlement Agreement, the Vogtle Owners will forbear from exercising certain remedies, including drawing on the Westinghouse Letters of Credit, until June 30, 2020, unless certain events of nonpayment, insolvency, or other material breach of the Guarantee Settlement Agreement by Toshiba occur. If such an event occurs, the balance of the Guarantee Obligations will become immediately due and payable, and the Vogtle Owners may exercise any and all rights and remedies, including drawing on the Westinghouse Letters of Credit without restriction. In addition, the Guarantee Settlement Agreement does not restrict the Vogtle Owners from fully drawing on the Westinghouse Letters of Credit in the event they are not renewed or replaced prior to the expiration date. On June 23, 2017, Toshiba released a revised outlook for fiscal year 2016, which reflected a negative shareholders' equity balance of approximately $5 billion as of March 31, 2017, and announced that its independent audit process was continuing. Toshiba has also announced the existence of material events and conditions that raise substantial doubt about Toshiba's ability to continue as a going concern. As a result, substantial risk regarding the Vogtle Owners' ability to fully collect the Guarantee Obligations continues to exist. An inability or other failure by Toshiba to perform its obligations under the Guarantee Settlement Agreement could have a further material impact on the net cost to the Vogtle Owners to complete construction of Plant Vogtle Units 3 and 4 and, therefore, on Southern Company's and Georgia Power's financial statements. Additionally, on June 9, 2017, Georgia Power, acting for itself and as agent for the other Vogtle Owners, and the EPC Contractor entered into a services agreement (Services Agreement), which was amended and restated on July 20, 2017, for the EPC Contractor to transition construction management of Plant Vogtle Units 3 and 4 to Southern Nuclear and to provide ongoing design, engineering, and procurement services to Southern Nuclear. On July 20, 2017, the bankruptcy court approved the EPC Contractor's motion seeking authorization to (i) enter into the Services Agreement, (ii) assume and assign to the Vogtle Owners certain project-related contracts, (iii) join the Vogtle Owners as counterparties to certain assumed project-related contracts, and (iv) reject the Vogtle 3 and 4 Agreement. The Services Agreement, and the EPC Contractor's rejection of the Vogtle 3 and 4 Agreement, became effective upon approval by the DOE on July 27, 2017. The Services Agreement will continue until the start-up and testing of Plant Vogtle Units 3 and 4 is complete and electricity is generated and sold from both units. The Services Agreement is terminable by the Vogtle Owners upon 30 days' written notice. 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 nuclear construction projects certified by the Georgia PSC. Financing costs are recovered on all applicable certified costs through annual adjustments to the NCCR tariff by including the related CWIP accounts in rate base during the construction period. As of June 30, 2017 , Georgia Power had recovered approximately $1.4 billion of financing costs. On December 20, 2016, the Georgia PSC voted to approve a settlement agreement (Vogtle Cost Settlement Agreement) resolving the following prudence matters: (i) none of the $3.3 billion of costs incurred through December 31, 2015 and reflected in the fourteenth VCM report will be disallowed from rate base on the basis of imprudence; (ii) the Contractor Settlement Agreement is reasonable and prudent and none of the amounts paid or to be paid pursuant to the Contractor Settlement Agreement should be disallowed from rate base on the basis of imprudence; (iii) financing costs on verified and approved capital costs will be deemed prudent provided they are incurred prior to December 31, 2019 and December 31, 2020 for Plant Vogtle Units 3 and 4, respectively; and (iv) (a) the in-service capital cost forecast will be adjusted to $5.680 billion (Revised Forecast), which includes a contingency of $240 million above Georgia Power's then current forecast of $5.440 billion , (b) capital costs incurred up to the Revised Forecast will be presumed to be reasonable and prudent with the burden of proof on any party challenging such costs, and (c) Georgia Power would hav

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS As of June 30, 2017 , 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 June 30, 2017: 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)(b) $ 193 $ 179 $ — $ — $ 372 Interest rate derivatives — 11 — — 11 Foreign currency derivatives — 56 — — 56 Nuclear decommissioning trusts (c) 728 966 — 25 1,719 Cash equivalents 834 — — — 834 Other investments 9 — 1 — 10 Total $ 1,764 $ 1,212 $ 1 $ 25 $ 3,002 Liabilities: Energy-related derivatives (a)(b) $ 205 $ 161 $ — $ — $ 366 Interest rate derivatives — 23 — — 23 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 20 — 20 Total $ 205 $ 207 $ 20 $ — $ 432 Alabama Power Assets: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Nuclear decommissioning trusts: (d) Domestic equity 411 79 — — 490 Foreign equity 56 54 — — 110 U.S. Treasury and government agency securities — 29 — — 29 Corporate bonds 22 145 — — 167 Mortgage and asset backed securities — 18 — — 18 Private Equity — — — 25 25 Other — 6 — — 6 Cash equivalents 493 — — — 493 Total $ 982 $ 340 $ — $ 25 $ 1,347 Liabilities: Energy-related derivatives $ — $ 11 $ — $ — $ 11 Fair Value Measurements Using: As of June 30, 2017: 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) Georgia Power Assets: Energy-related derivatives $ — $ 15 $ — $ — $ 15 Interest rate derivatives — 1 — — 1 Nuclear decommissioning trusts: (d) (e) Domestic equity 225 1 — — 226 Foreign equity — 147 — — 147 U.S. Treasury and government agency securities — 198 — — 198 Municipal bonds — 72 — — 72 Corporate bonds — 169 — — 169 Mortgage and asset backed securities — 41 — — 41 Other 14 7 — — 21 Cash equivalents 50 — — — 50 Total $ 289 $ 651 $ — $ — $ 940 Liabilities: Energy-related derivatives $ — $ 14 $ — $ — $ 14 Interest rate derivatives — 3 — — 3 Total $ — $ 17 $ — $ — $ 17 Gulf Power Assets: Energy-related derivatives $ — $ 1 $ — $ — $ 1 Cash equivalents 21 — — — 21 Total $ 21 $ 1 $ — $ — $ 22 Liabilities: Energy-related derivatives $ — $ 29 $ — $ — $ 29 Mississippi Power Assets: Energy-related derivatives $ — $ 2 $ — $ — $ 2 Interest rate derivatives — 3 — — 3 Cash equivalents 100 — — — 100 Total $ 100 $ 5 $ — $ — $ 105 Liabilities: Energy-related derivatives $ — $ 10 $ — $ — $ 10 Fair Value Measurements Using: As of June 30, 2017: 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 Power Assets: Energy-related derivatives $ — $ 14 $ — $ — $ 14 Foreign currency derivatives — 56 — — 56 Total $ — $ 70 $ — $ — $ 70 Liabilities: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 20 — 20 Total $ — $ 32 $ 20 $ — $ 52 Southern Company Gas Assets: Energy-related derivatives (a)(b) $ 193 $ 138 $ — $ — $ 331 Liabilities: Energy-related derivatives (a)(b) $ 205 $ 86 $ — $ — $ 291 (a) Excludes $11 million associated with certain weather derivatives accounted for based on intrinsic value rather than fair value. (b) Excludes cash collateral of $71 million . (c) For additional detail, see the nuclear decommissioning trusts sections for Alabama Power and Georgia Power in this table. (d) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. (e) Includes the investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of June 30, 2017 , approximately $38 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. 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 at Southern Company, including reinvested interest and dividends and excluding the funds' expenses, increased by $55 million and $118 million , respectively, for the three and six months ended June 30, 2017 , and by $47 million and $67 million , respectively, for the three and six months ended June 30, 2016 . Alabama Power recorded an increase in fair value of $28 million and $62 million , respectively, for the three and six months ended June 30, 2017 and $29 million and $40 million , respectively, for the three and six months ended June 30, 2016 as a change in regulatory liabilities related to its AROs. Georgia Power recorded increases in fair value of $27 million and $56 million , respectively, for the three and six months ended June 30, 2017 and $18 million and $27 million , respectively, for the three and six months ended June 30, 2016 as a change in its regulatory asset related to its AROs. 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 (H) for additional information on how these derivatives are used. The NRC requires licensees of commissioned nuclear power reactors to establish a plan for providing reasonable assurance of funds for future decommissioning. For fair value measurements of the investments within the nuclear decommissioning 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. See Note 1 to the financial statements of Southern Company, Alabama Power, and Georgia Power 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 obligated to make generation-based payments to the seller over a period ranging from 10 to 30 years, beginning at the commercial operation date. 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, and is evaluated periodically. The fair value of contingent consideration reflects the net present value of expected payments and any periodic change arising from forecasted generation is expected to be immaterial. "Other investments" include investments that are not traded in the open market. The fair value of these investments has been determined based on market factors including comparable multiples and the expectations regarding cash flows and business plan executions. As of June 30, 2017 , the fair value measurements of private equity investments held in the nuclear decommissioning trust that are calculated at net asset value per share (or its equivalent) as a practical expedient, as well as the nature and risks of those investments, were as follows: As of June 30, 2017: Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period (in millions) Southern Company $ 25 $ 22 Not Applicable Not Applicable Alabama Power $ 25 $ 22 Not Applicable Not Applicable Private equity funds include a fund-of-funds that invests 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. Liquidations are expected to occur at various times over the next 10 years . As of June 30, 2017 , other financial instruments for which the carrying amount did not equal fair value were as follows: Carrying Amount Fair Value (in millions) Long-term debt, including securities due within one year: Southern Company $ 46,631 $ 48,228 Alabama Power $ 7,440 $ 8,041 Georgia Power $ 10,888 $ 11,585 Gulf Power $ 1,292 $ 1,336 Mississippi Power $ 2,125 $ 2,071 Southern Power $ 5,725 $ 5,878 Southern Company Gas $ 5,699 $ 6,031 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, Gulf Power, Mississippi Power, Southern Power, and Southern Company Gas.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY Earnings per Share For Southern Company, the only difference in computing basic and diluted earnings per share is attributable to awards outstanding under the stock option and performance share plans. See Note 8 to the financial statements of Southern Company in Item 8 of the Form 10-K for information on the stock option and performance share plans. The effect of both stock options and performance share award units was determined using the treasury stock method. Shares used to compute diluted earnings per share were as follows: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) As reported shares 998 934 996 925 Effect of options and performance share award units 7 6 7 6 Diluted shares 1,005 940 1,003 931 Stock options and performance share award units that were not included in the diluted earnings per share calculation because they were anti-dilutive were immaterial for the three and six months ended June 30, 2017 and 2016 . Changes in Stockholders' Equity The following table presents year-to-date changes in stockholders' equity of Southern Company: Number of Common Shares Common Preferred and Preference Stock of Subsidiaries Total Issued Treasury Noncontrolling Interests (*) (in thousands) (in millions) Balance at December 31, 2016 991,213 (819 ) $ 24,758 $ 609 $ 1,245 $ 26,612 Consolidated net income (loss) attributable to Southern Company — — (723 ) — — (723 ) Other comprehensive income (loss) — — (11 ) — — (11 ) Stock issued 9,129 — 417 — — 417 Stock-based compensation — — 72 — — 72 Cash dividends on common stock — — (1,134 ) — — (1,134 ) Preference stock redemption — — — (150 ) — (150 ) Contributions from noncontrolling interests — — — 71 71 Distributions to noncontrolling interests — — — — (40 ) (40 ) Net income attributable to noncontrolling interests — — — — 16 16 Reclassification from redeemable noncontrolling interests — — — — 114 114 Other — (49 ) (7 ) 3 1 (3 ) Balance at June 30, 2017 1,000,342 (868 ) $ 23,372 $ 462 $ 1,407 $ 25,241 Balance at December 31, 2015 915,073 (3,352 ) $ 20,592 $ 609 $ 781 $ 21,982 Consolidated net income attributable to Southern Company — — 1,112 — — 1,112 Other comprehensive income (loss) — — (117 ) — — (117 ) Stock issued 27,297 2,599 1,383 — — 1,383 Stock-based compensation — — 67 — — 67 Cash dividends on common stock — — (1,023 ) — — (1,023 ) Contributions from noncontrolling interests — — — — 169 169 Distributions to noncontrolling interests — — — — (10 ) (10 ) Purchase of membership interests from noncontrolling interests — — — — (129 ) (129 ) Net income attributable to noncontrolling interests — — — — 11 11 Other — (19 ) 1 — — 1 Balance at June 30, 2016 942,370 (772 ) $ 22,015 $ 609 $ 822 $ 23,446 (*) Related to Southern Power Company and excludes redeemable noncontrolling interests. In April 2017, approximately $114 million was reclassified from redeemable noncontrolling interests to noncontrolling interests, included in stockholder's equity, due to the expiration of SunPower Corp's option to require Southern Power to purchase its membership interests in one of the solar partnerships. See Note 10 to the financial statements of Southern Power in Item 8 of the Form 10-K for additional information.

Financing

Financing	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
FINANCING	FINANCING Going Concern As of June 30, 2017 , Mississippi Power's current liabilities exceeded current assets by approximately $930 million primarily due to approximately $935 million that will be required through June 30, 2018 to fund maturities of long-term debt and $17 million that will be required to fund maturities of short-term debt. In addition, Mississippi Power has $40 million of tax-exempt variable rate demand obligations that are supported by short-term credit facilities and $50 million of fixed rate pollution control revenue bonds that are required to be remarketed over the next 12 months. Mississippi Power intends to utilize operating cash flows, lines of credit, and bank term loans, as market conditions permit, as well as, under certain circumstances, commercial paper and/or equity contributions and/or loans from Southern Company to fund Mississippi Power's short-term capital needs. Specifically, Mississippi Power has been informed by Southern Company that in the event sufficient funds are not available from external sources, Southern Company intends to provide Mississippi Power with loans and/or equity contributions sufficient to fund the remaining indebtedness scheduled to mature and other cash needs over the next 12 months. Therefore, Mississippi Power's financial statement presentation contemplates continuation of Mississippi Power as a going concern as a result of Southern Company's anticipated ongoing financial support of Mississippi Power. For additional information, see Notes 1 and 6 to the financial statements of Mississippi Power under "Recently Issued Accounting Standards" and "Going Concern," respectively, in Item 8 of the Form 10-K and Note (B) under " Integrated Coal Gasification Combined Cycle ." DOE Loan Guarantee Borrowings See Note 6 to the financial statements of Southern Company and Georgia Power in Item 8 of the Form 10-K for additional information regarding Georgia Power's loan guarantee agreement (Loan Guarantee Agreement) with the DOE and related multi-advance term loan facility (FFB Credit Facility) with the FFB. On July 27, 2017, Georgia Power entered into an amendment to the Loan Guarantee Agreement (LGA Amendment) in connection with the DOE's consent to Georgia Power's entry into the Services Agreement and the related intellectual property licenses (IP Licenses). The purpose of the amendment is to clarify the operation of the Loan Guarantee Agreement pending Georgia Power's completion of its comprehensive schedule, cost-to-complete, and cancellation cost assessments being prepared as a result of the bankruptcy of the EPC Contractor (Cost Assessments). Under the terms of the Loan Guarantee Agreement, upon termination of the Vogtle 3 and 4 Agreement, further advances are conditioned upon the DOE's approval of any agreements entered into in replacement of the Vogtle 3 and 4 Agreement. Under the terms of the LGA Amendment, Georgia Power will not request any advances unless and until such time as Georgia Power has (i) completed the Cost Assessments and made a determination to continue construction of Plant Vogtle Units 3 and 4, (ii) delivered to the DOE an updated project schedule, construction budget, and other information, (iii) entered into one or more agreements with a construction contractor or contractors that will be primarily responsible for construction of Plant Vogtle Units 3 and 4 and such agreements have been approved by the DOE (together with the Services Agreement and the IP Licenses, the Replacement EPC Arrangements), and (iv) entered into a further amendment to the Loan Guarantee Agreement with the DOE to reflect the Replacement EPC Arrangements. Upon satisfaction of the conditions described above, advances may be requested under the FFB Credit Facility on a quarterly basis through 2020. The final maturity date for each advance under the FFB Credit Facility is February 20, 2044. Interest is payable quarterly and principal payments will begin on February 20, 2020. Borrowings under the FFB Credit Facility will bear interest at the applicable U.S. Treasury rate plus a spread equal to 0.375% . 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, accuracy of project-related representations and warranties, delivery of updated project-related information, absence of liens on Georgia Power's ownership interest in Plant Vogtle Units 3 and 4 other than permitted liens, 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. Under the 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 Facility will terminate and Georgia Power will be required to prepay the outstanding principal amount of all borrowings under the FFB Credit Facility over a period of five years (with level principal amortization). Among other things, these mandatory prepayment events include (i) the termination of the Services Agreement or rejection of the Services Agreement in bankruptcy if Georgia Power does not maintain access to intellectual property rights under the IP Licenses; (ii) a decision by Georgia Power not to continue construction of Plant Vogtle Units 3 and 4; (iii) a failure by Georgia Power to complete the Cost Assessments or enter into Replacement EPC Arrangements by December 31, 2017; (iv) cancellation of Plant Vogtle Units 3 and 4 by the Georgia PSC, or by Georgia Power if authorized by the Georgia PSC; and (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 Facility. 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 Facility. In addition, under certain circumstances Georgia Power may be required to make additional prepayments in connection with its receipt of payments under the Guarantee Settlement Agreement or from the EPC Contractor under the Vogtle 3 and 4 Agreement. Georgia Power also may voluntarily prepay outstanding borrowings under the FFB Credit Facility. Under the FFB Credit Facility, any prepayment (whether mandatory or optional) will be made with a make-whole premium or discount, as applicable. See Note (B) under " Regulatory Matters – Georgia Power – Nuclear Construction " for additional information regarding Plant Vogtle Units 3 and 4. Bank Credit Arrangements Bank credit arrangements provide liquidity support to the registrants' commercial paper borrowings and the traditional electric operating companies' pollution control revenue bonds. The amount of variable rate pollution control revenue bonds of the traditional electric operating companies outstanding requiring liquidity support as of June 30, 2017 was approximately $1.6 billion (comprised of approximately $890 million at Alabama Power, $550 million at Georgia Power, $82 million at Gulf Power, and $40 million at Mississippi Power). In June 2017, Georgia Power remarketed $318 million of variable rate pollution control bonds in index rate modes, reducing the liquidity support utilized under Georgia Power's bank credit arrangement. In addition, at June 30, 2017 , the traditional electric operating companies had approximately $626 million (comprised of approximately $436 million at Georgia Power, $140 million at Gulf Power, and $50 million at Mississippi Power) of pollution control revenue bonds outstanding that were required to be reoffered within the next 12 months. See Note 6 to the financial statements of each registrant 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 June 30, 2017 : Expires Executable Term Loans Expires Within One Year Company 2017 2018 2019 2020 2022 Total Unused One Year Two Years Term Out No Term Out (in millions) Southern Company (a) $ — $ — $ — $ — $ 2,000 $ 2,000 $ 2,000 $ — $ — $ — $ — Alabama Power 3 532 — — 800 1,335 1,335 — — — 35 Georgia Power — — — — 1,750 1,750 1,732 — — — — Gulf Power 30 195 25 30 — 280 280 45 — — 40 Mississippi Power 113 — — — — 113 100 — 13 13 100 Southern Power Company — — — — 750 750 675 — — — — Southern Company Gas (b) — — — — 1,900 1,900 1,849 — — — — Other 10 30 — — — 40 40 20 — 20 20 Southern Company Consolidated $ 156 $ 757 $ 25 $ 30 $ 7,200 $ 8,168 $ 8,011 $ 65 $ 13 $ 33 $ 195 (a) Represents the Southern Company parent entity. (b) Southern Company Gas, as the parent entity, guarantees the obligations of Southern Company Gas Capital, which is the borrower of $1.2 billion of these arrangements. Southern Company Gas' committed credit arrangements also include $700 million for which Nicor Gas is the borrower and which is restricted for working capital needs of Nicor Gas. As reflected in the table above, in May 2017, Southern Company, Alabama Power, Georgia Power, and Southern Power Company each amended certain of their multi-year credit arrangements, which, among other things, extended the maturity dates from 2020 to 2022. Southern Company and Southern Power Company increased their borrowing ability under these arrangements to $2.0 billion from $1.25 billion and to $750 million from $600 million , respectively. Southern Company also terminated its $1.0 billion facility maturing in 2018. Also in May 2017, Southern Company Gas Capital and Nicor Gas terminated their existing credit arrangements for $1.3 billion and $700 million , respectively, which were to mature in 2017 and 2018, and entered into a new multi-year credit arrangement currently allocated for $1.2 billion and $700 million , respectively, with a maturity date of 2022. 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. Financing Activities The following table outlines the long-term debt financing activities for Southern Company and its subsidiaries for the first six months of 2017 : Company Senior Note Issuances Senior Note Maturities and Redemptions Revenue Bond Other Long-Term Debt Issuances Other Long-Term Debt Redemptions and Maturities (a) (in millions) Southern Company (b) $ 300 $ — $ — $ 500 $ 400 Alabama Power 550 200 — — — Georgia Power 850 450 27 — 3 Gulf Power 300 85 — 6 — Mississippi Power — — — 40 893 Southern Power — — — 3 3 Southern Company Gas (c) 450 — — — — Other — — — — 8 Elimination (d) — — — (40 ) (591 ) Southern Company Consolidated $ 2,450 $ 735 $ 27 $ 509 $ 716 (a) Includes reductions in capital lease obligations resulting from cash payments under capital leases. (b) Represents the Southern Company parent entity. (c) The senior notes were issued by Southern Company Gas Capital and guaranteed by the Southern Company Gas parent entity. (d) Intercompany loans from Southern Company to Mississippi Power eliminated in Southern Company's Consolidated Financial Statements. Southern Company In June 2017, Southern Company issued $500 million aggregate principal amount of Series 2017A 5.325% Junior Subordinated Notes due June 21, 2057. The proceeds were used to repay short-term indebtedness and for other general corporate purposes. Also in June 2017, Southern Company issued $300 million aggregate principal amount of Series 2017A Floating Rate Senior Notes due September 30, 2020, which bear interest at a floating rate based on three -month LIBOR. The proceeds were used to repay short-term indebtedness and for other general corporate purposes. Also in June 2017, Southern Company entered into two $100 million aggregate principal amount floating rate bank term loan agreements, which mature on June 21, 2018 and June 29, 2018 and bear interest based on one -month LIBOR. The proceeds were used for working capital and other general corporate purposes. Alabama Power In March 2017, Alabama Power issued $550 million aggregate principal amount of Series 2017A 2.45% Senior Notes due March 30, 2022. The proceeds were used to repay Alabama Power's short-term indebtedness and for general corporate purposes, including Alabama Power's continuous construction program. Georgia Power In March 2017, Georgia Power issued $450 million aggregate principal amount of Series 2017A 2.00% Senior Notes due March 30, 2020 and $400 million aggregate principal amount of Series 2017B 3.25% Senior Notes due March 30, 2027. The proceeds were used to repay a portion of Georgia Power's short-term indebtedness and for general corporate purposes, including Georgia Power's continuous construction program. In April 2017, Georgia Power purchased and held $27 million aggregate principal amount of Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1995. Georgia Power may reoffer these bonds to the public at a later date. In June 2017, Georgia Power entered into three floating rate bank loans in aggregate principal amounts of $50 million , $150 million , and $100 million , which mature on December 1, 2017, May 31, 2018, and June 28, 2018, respectively, and bear interest based on one -month LIBOR. Also in June 2017, Georgia Power borrowed $500 million pursuant to an uncommitted bank credit arrangement, which bears interest at a rate agreed upon by Georgia Power and the bank from time to time and is payable on no less than 30 days' demand by the bank. The proceeds from these bank loans were used to repay a portion of Georgia Power's existing indebtedness and for working capital and other general corporate purposes, including Georgia Power's continuous construction program. Gulf Power In March 2017, Gulf Power extended the maturity of a $100 million short-term floating rate bank loan bearing interest based on one -month LIBOR from April 2017 to October 2017 and subsequently repaid the loan in May 2017. In May 2017, Gulf Power issued $300 million aggregate principal amount of Series 2017A 3.30% Senior Notes due May 30, 2027. The proceeds, together with other funds, were used to repay at maturity $85 million aggregate principal amount of Series 2007A 5.90% Senior Notes due June 15, 2017; to repay outstanding commercial paper borrowings; to repay a $100 million short-term floating rate bank loan, as discussed above; and to redeem 550,000 shares ( $55 million aggregate liquidation amount) of Gulf Power's 6.00% Series Preference Stock, 450,000 shares ( $45 million aggregate liquidation amount) of Gulf Power's Series 2007A 6.45% Preference Stock, and 500,000 shares ( $50 million aggregate liquidation amount) of Gulf Power's Series 2013A 5.60% Preference Stock. Mississippi Power In March 2017, Mississippi Power issued a $9 million short-term bank note bearing interest at 5% per annum, which was repaid in April 2017. In February 2017, Mississippi Power amended $551 million in promissory notes to Southern Company extending the maturity dates of the notes from December 1, 2017 to July 31, 2018. In the second quarter 2017, Mississippi Power borrowed an additional $40 million under a promissory note issued to Southern Company. In June 2017, Southern Company made equity contributions totaling $1.0 billion to Mississippi Power. Mississippi Power used a portion of the proceeds to (i) prepay $300 million of the outstanding principal amount under its $1.2 billion unsecured term loan, which matures on March 30, 2018; (ii) repay all of the $591 million outstanding principal amount of promissory notes to Southern Company; and (iii) repay a $10 million short-term bank loan. Southern Company Gas In May 2017, Southern Company Gas Capital issued $450 million aggregate principal amount of Series 2017A 4.40% Senior Notes due May 30, 2047. The proceeds were used to repay Southern Company Gas' short-term indebtedness and for general corporate purposes.

Retirement Benefits

Retirement Benefits	6 Months Ended
	Jun. 30, 2017
Retirement Benefits [Abstract]
RETIREMENT BENEFITS	RETIREMENT BENEFITS Southern Company has a defined benefit, trusteed, pension plan covering substantially all employees, with the exception of employees at Southern Company Gas, as discussed below, and PowerSecure. The Southern Company 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 Southern Company qualified pension plan are anticipated for the year ending December 31, 2017 . Southern Company also provides certain defined benefit pension plans for a selected group of management and highly compensated employees. Benefits under these non-qualified pension plans are funded on a cash basis. In addition, Southern Company provides certain medical care and life insurance benefits for retired employees through other postretirement benefit plans. The traditional electric operating companies fund related other postretirement trusts to the extent required by their respective regulatory commissions. In addition, Southern Company Gas has a qualified defined benefit, trusteed, pension plan covering certain eligible employees, which was closed in 2012 to new employees. This qualified pension plan is funded in accordance with requirements of ERISA. No mandatory contributions to the Southern Company Gas qualified pension plan are anticipated for the year ending December 31, 2017 . Southern Company Gas also provides certain non-qualified defined benefit and defined contribution pension plans for a selected group of management and highly compensated employees. Benefits under these non-qualified pension plans are funded on a cash basis. In addition, Southern Company Gas provides certain medical care and life insurance benefits for eligible retired employees through a postretirement benefit plan. Southern Company Gas also has a separate unfunded supplemental retirement health care plan that provides medical care and life insurance benefits to employees of discontinued businesses. See Note 2 to the financial statements of Southern Company, Alabama Power, Georgia Power, Gulf Power, Mississippi Power, and Southern Company Gas in Item 8 of the Form 10-K for additional information. Components of the net periodic benefit costs for the three and six months ended June 30, 2017 and 2016 are presented in the following tables. Pension Plans Southern Company Alabama Power Georgia Power Gulf Power Mississippi Power (in millions) Three Months Ended June 30, 2017 Service cost $ 74 $ 16 $ 18 $ 4 $ 3 Interest cost 113 24 35 5 5 Expected return on plan assets (225 ) (49 ) (70 ) (9 ) (10 ) Amortization: Prior service costs 3 — 1 — 1 Net (gain)/loss 41 11 14 1 2 Net periodic pension cost (income) $ 6 $ 2 $ (2 ) $ 1 $ 1 Six Months Ended June 30, 2017 Service cost $ 147 $ 32 $ 37 $ 7 $ 7 Interest cost 227 48 69 10 10 Expected return on plan assets (449 ) (98 ) (141 ) (19 ) (20 ) Amortization: Prior service costs 6 1 2 — 1 Net (gain)/loss 81 21 28 3 4 Net periodic pension cost (income) $ 12 $ 4 $ (5 ) $ 1 $ 2 Three Months Ended June 30, 2016 Service cost $ 62 $ 15 $ 18 $ 3 $ 3 Interest cost 101 24 34 4 5 Expected return on plan assets (187 ) (46 ) (65 ) (8 ) (8 ) Amortization: Prior service costs 3 — 2 1 — Net (gain)/loss 37 10 13 1 1 Net periodic pension cost $ 16 $ 3 $ 2 $ 1 $ 1 Six Months Ended June 30, 2016 Service cost $ 124 $ 29 $ 35 $ 6 $ 6 Interest cost 201 48 68 9 10 Expected return on plan assets (374 ) (92 ) (129 ) (17 ) (17 ) Amortization: Prior service costs 7 1 3 1 — Net (gain)/loss 75 20 27 3 3 Net periodic pension cost $ 33 $ 6 $ 4 $ 2 $ 2 Pension Plans Southern Company Gas (in millions) Successor – Three Months Ended June 30, 2017 Service cost $ 5 Interest cost 10 Expected return on plan assets (17 ) Amortization: Prior service costs (1 ) Net (gain)/loss 5 Net periodic pension cost $ 2 Successor – Six Months Ended June 30, 2017 Service cost $ 11 Interest cost 20 Expected return on plan assets (35 ) Amortization: Prior service costs (1 ) Net (gain)/loss 10 Net periodic pension cost $ 5 Predecessor – Three Months Ended June 30, 2016 Service cost $ 7 Interest cost 11 Expected return on plan assets (17 ) Amortization: Prior service costs (1 ) Net (gain)/loss 7 Net periodic pension cost $ 7 Predecessor – Six Months Ended June 30, 2016 Service cost $ 13 Interest cost 21 Expected return on plan assets (33 ) Amortization: Prior service costs (1 ) Net (gain)/loss 13 Net periodic pension cost $ 13 Postretirement Benefits Southern Company Alabama Power Georgia Power Gulf Power Mississippi Power (in millions) Three Months Ended June 30, 2017 Service cost $ 6 $ 2 $ 1 $ 1 $ 1 Interest cost 20 4 8 — 1 Expected return on plan assets (17 ) (8 ) (6 ) (1 ) (1 ) Amortization: Prior service costs 1 1 1 — — Net (gain)/loss 5 1 1 — — Net periodic postretirement benefit cost $ 15 $ — $ 5 $ — $ 1 Six Months Ended June 30, 2017 Service cost $ 12 $ 3 $ 3 $ 1 $ 1 Interest cost 40 9 15 1 2 Expected return on plan assets (33 ) (14 ) (12 ) (1 ) (1 ) Amortization: Prior service costs 3 2 1 — — Net (gain)/loss 7 1 3 — — Net periodic postretirement benefit cost $ 29 $ 1 $ 10 $ 1 $ 2 Three Months Ended June 30, 2016 Service cost $ 6 $ 2 $ 1 $ 1 $ 1 Interest cost 17 4 7 — 1 Expected return on plan assets (14 ) (7 ) (5 ) (1 ) (1 ) Amortization: Prior service costs 1 1 1 — — Net (gain)/loss 4 1 2 — — Net periodic postretirement benefit cost $ 14 $ 1 $ 6 $ — $ 1 Six Months Ended June 30, 2016 Service cost $ 11 $ 3 $ 3 $ 1 $ 1 Interest cost 35 9 15 1 2 Expected return on plan assets (28 ) (13 ) (11 ) (1 ) (1 ) Amortization: Prior service costs 3 2 1 — — Net (gain)/loss 7 1 4 — — Net periodic postretirement benefit cost $ 28 $ 2 $ 12 $ 1 $ 2 Postretirement Benefits Southern Company Gas (in millions) Successor – Three Months Ended June 30, 2017 Service cost $ — Interest cost 2 Expected return on plan assets (1 ) Amortization: Prior service costs — Net (gain)/loss 1 Net periodic postretirement benefit cost $ 2 Successor – Six Months Ended June 30, 2017 Service cost $ 1 Interest cost 5 Expected return on plan assets (3 ) Amortization: Prior service costs (1 ) Net (gain)/loss 2 Net periodic postretirement benefit cost $ 4 Predecessor – Three Months Ended June 30, 2016 Service cost $ — Interest cost 2 Expected return on plan assets (1 ) Amortization: Prior service costs — Net (gain)/loss 1 Net periodic postretirement benefit cost $ 2 Predecessor – Six Months Ended June 30, 2016 Service cost $ 1 Interest cost 5 Expected return on plan assets (3 ) Amortization: Prior service costs (1 ) Net (gain)/loss 2 Net periodic postretirement benefit cost $ 4

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES See Note 5 to the financial statements of each registrant 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 $1.9 billion as of June 30, 2017 compared to $1.8 billion as of December 31, 2016 . The federal ITC carryforwards begin expiring in 2032 but are expected to be fully utilized by 2022. The PTC carryforwards begin expiring in 2036 but are expected to be utilized by 2022. The expected utilization of tax credit carryforwards could be further delayed by numerous factors. These factors include the acquisition of additional renewable projects, increased generation at existing wind facilities, carrying back the federal net operating loss, and potential tax reform legislation, as well as additional deductions in the event of an asset abandonment. The ultimate outcome of these matters cannot be determined at this time. Valuation Allowances At June 30, 2017 , valuation allowances were as follows: Mississippi Power Southern Company Gas Southern Company (in millions) Federal $ — $ 18 $ 18 State (net of federal benefit) 46 1 63 Balance at June 30, 2017 $ 46 $ 19 $ 81 Southern Company had valuation allowances, net of the federal benefit, of $81 million at June 30, 2017 compared to $21 million at December 31, 2016. The increase was primarily due to Mississippi Power's projected inability to utilize the State of Mississippi net operating loss. Effective Tax Rate 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 federal income tax benefits from ITCs and PTCs. Southern Company's effective tax (benefit) rate was (28.6)% for the six months ended June 30, 2017 compared to 29.4% for the corresponding period in 2016 . The effective tax rate decrease was primarily due to the estimated probable losses on the Kemper IGCC, net of the non-deductible AFUDC equity portion. Other factors include an increase in tax benefits from wind PTCs and state apportionment rate changes, partially offset by a decrease in tax benefits from ITCs and an increase in state valuation allowances. Southern Company recognizes PTCs when wind energy is generated and sold (using the prescribed KWH rate in applicable federal and state statutes), which may differ significantly from amounts computed on a quarterly basis using an overall estimated annual effective income tax rate. Southern Company uses this method of recognition since the amount of PTCs can be significantly impacted by wind generation. This method can significantly affect the effective income tax rate for the period depending on the amount of pretax income. Mississippi Power Mississippi Power's effective tax (benefit) rate was (30.5)% for the six months ended June 30, 2017 compared to (208.1)% for the corresponding period in 2016 . The effective tax rate increase was primarily due to the estimated probable losses on the Kemper IGCC, net of the non-deductible AFUDC equity portion and the related state valuation allowances. Southern Power Southern Power's effective tax (benefit) rate was (114.7)% for the six months ended June 30, 2017 compared to (74.0)% for the corresponding period in 2016 . The effective tax rate decrease was primarily due to additional PTCs arising from Southern Power's wind facility acquisitions, state apportionment rate changes, and lower pre-tax earnings, partially offset by a decrease in tax benefits from ITCs. Southern Power recognizes PTCs when wind energy is generated and sold (using the prescribed KWH rate in applicable federal and state statutes), which may differ significantly from amounts computed on a quarterly basis using an overall estimated annual effective income tax rate. Southern Power uses this method of recognition since the amount of PTCs can be significantly impacted by wind generation. This method can significantly affect the effective income tax rate for the period depending on the amount of pretax income. Unrecognized Tax Benefits See Note 5 to the financial statements of each registrant under "Unrecognized Tax Benefits" in Item 8 of the Form 10-K for additional information. Changes during the six months ended June 30, 2017 for unrecognized tax benefits were as follows: Mississippi Power Southern Power Southern Company (in millions) Unrecognized tax benefits as of December 31, 2016 $ 465 $ 17 $ 484 Tax positions from current periods 3 1 10 Tax positions from prior periods — 1 7 Balance as of June 30, 2017 $ 468 $ 19 $ 501 The tax positions from current and prior periods primarily relate to state tax benefits and charitable contribution carryforwards that will be impacted as a result of the proposed settlement of R&E expenditures associated with the Kemper IGCC. See " Section 174 Research and Experimental Deduction " herein for additional information. These amounts are presented on a gross basis without considering the related federal or state income tax impact. The impact on the effective tax rate, if recognized, is as follows: As of June 30, 2017 As of December 31, 2016 Mississippi Power Southern Power Southern Company Southern Company (in millions) Tax positions impacting the effective tax rate $ 4 $ 19 $ 37 $ 20 Tax positions not impacting the effective tax rate 464 — 464 464 Balance of unrecognized tax benefits $ 468 $ 19 $ 501 $ 484 The tax positions impacting the effective tax rate primarily relate to federal deferred income tax credits and Southern Company's estimate of the uncertainty related to the amount of those benefits, and state tax benefits and charitable contribution carryforwards that will be impacted as a result of the proposed settlement of R&E expenditures associated with the Kemper IGCC. See " Section 174 Research and Experimental Deduction " herein for additional information. If these tax positions are not able to be recognized due to a federal audit adjustment in the amount that has been estimated, the amount of tax credit carryforwards discussed above would be reduced by approximately $98 million . Accrued interest for all tax positions other than the Section 174 R&E deductions was immaterial for all periods presented. All of the registrants classify interest on tax uncertainties as interest expense. None of the registrants accrued any penalties on uncertain tax positions. It is reasonably possible that the amount of the unrecognized tax benefits could change within 12 months . The settlement of federal and state audits and the U.S. Congress Joint Committee on Taxation approval of the R&E expenditures associated with the Kemper IGCC could impact the balances significantly. At this time, an estimate of the range of reasonably possible outcomes cannot be determined. See " Section 174 Research and Experimental Deduction " herein for more information. The IRS has finalized its audits of Southern Company's consolidated federal income tax returns through 2012. Southern Company has filed its 2013, 2014, and 2015 federal income tax returns and has received partial acceptance letters from the IRS; however, the IRS has not finalized its audits. Southern Company is a participant in the Compliance Assurance Process of the IRS. In addition, the pre-Merger Southern Company Gas 2014 federal tax return is currently under audit. The audits for Southern Company's state income tax returns have either been concluded, or the statute of limitations has expired, for years prior to 2011. Section 174 Research and Experimental Deduction Southern Company reflected deductions for R&E expenditures related to the Kemper IGCC in its federal income tax calculations since 2013 and filed amended federal income tax returns for 2008 through 2013 to also include such deductions. The Kemper IGCC is based on first-of-a-kind technology, and Southern Company and Mississippi Power believe that a significant portion of the plant costs qualify as deductible R&E expenditures under IRC Section 174. In December 2016, Southern Company and the IRS reached a proposed settlement, subject to approval of the U.S. Congress Joint Committee on Taxation, resolving a methodology for these deductions. Due to the uncertainty related to this tax position, Southern Company and Mississippi Power had unrecognized tax benefits associated with these R&E deductions totaling approximately $464 million and associated interest of $36 million as of June 30, 2017 . If the suspension of the Kemper IGCC start-up activities results in an abandonment, any amount not allowed under IRC Section 174 would be claimed as a deduction under IRC Section 165, and would result in a reversal of the related unrecognized tax benefits, excluding interest. The ultimate outcome of this matter cannot be determined at this time.

Derivatives

Derivatives	6 Months Ended
	Jun. 30, 2017
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 (C) for additional information. In the statements of cash flows, the cash impacts of settled energy-related and interest rate derivatives are recorded as operating activities. The 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. Energy-Related Derivatives Southern Company, 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 is expected to continue to mitigate price volatility. The Florida PSC extended the moratorium on Gulf Power's fuel-hedging program through January 1, 2021 in connection with the 2017 Rate Case Settlement Agreement. The moratorium does not have an impact on the recovery of existing hedges entered into under the previously-approved hedging program. 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 the statements of income. Energy-related derivative contracts are accounted for under one of three methods: • Regulatory Hedges — Energy-related derivative contracts which are 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 OCI before being recognized in the statements of income in the same period as the hedged transactions are reflected in earnings. • 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 June 30, 2017 , the net volume of energy-related derivative contracts for natural gas positions for the Southern Company system, 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 (*) 472 2021 2024 Alabama Power 70 2020 — Georgia Power 160 2020 — Gulf Power 35 2020 — Mississippi Power 41 2021 — Southern Power 25 2017 — Southern Company Gas (*) 141 2019 2024 (*) Southern Company's and 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 3.5 billion mmBtu and short natural gas positions of 3.4 billion mmBtu as of June 30, 2017 , 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 gas due to operational constraints. The maximum expected volume of natural gas subject to such a feature is 31 million mmBtu for Southern Company, 10 million mmbtu for Georgia Power and Southern Power, 5 million mmbtu for Alabama Power, and 3 million mmBtu for Gulf Power and Mississippi Power. For cash flow hedges of energy-related derivatives, the amounts expected to be reclassified from accumulated OCI to earnings for the next 12 -month period ending June 30, 2018 are $6 million for Southern Power and immaterial for all other registrants. Interest Rate Derivatives Southern Company and certain subsidiaries may also 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 effective portion of the derivatives' fair value gains or losses is recorded in OCI and is reclassified into earnings at the same time the hedged transactions affect earnings, with any ineffectiveness recorded directly to earnings. 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, providing an offset, with any difference representing ineffectiveness. 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 June 30, 2017 , the following interest rate derivatives were outstanding: Notional Amount Interest Rate Received Weighted Average Interest Rate Paid Hedge Maturity Date Fair Value (in millions) (in millions) Cash Flow Hedges of Existing Debt Mississippi Power $ 900 1-month 0.79% March 2018 $ 3 Fair Value Hedges of Existing Debt Southern Company (*) 250 1.30% 3-month August 2017 — Southern Company (*) 300 2.75% 3-month June 2020 1 Southern Company (*) 1,500 2.35% 1-month July 2021 (14 ) Georgia Power 250 5.40% 3-month June 2018 — Georgia Power 500 1.95% 3-month December 2018 (2 ) Georgia Power 200 4.25% 3-month December 2019 1 Southern Company Consolidated $ 3,900 $ (11 ) (*) 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 next 12 -month period ending June 30, 2018 are $(21) million for Southern Company and immaterial for all other registrants. Southern Company and certain subsidiaries have deferred gains and losses expected to be amortized into earnings through 2046 . Foreign Currency Derivatives Southern Company and certain subsidiaries may also 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 effective portion of the derivatives' fair value gains or losses is recorded in OCI and is reclassified into earnings at the same time that the hedged transactions affect earnings, including foreign currency gains or losses arising from changes in the U.S. currency exchange rates. Any ineffectiveness is recorded directly to earnings. The derivatives employed as hedging instruments are structured to minimize ineffectiveness. At June 30, 2017 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ 18 Southern Power 564 3.78% 500 1.85% June 2026 15 Total $ 1,241 € 1,100 $ 33 The estimated pre-tax gains (losses) related to foreign currency derivatives that will be reclassified from accumulated OCI to earnings for the next 12 -month period ending June 30, 2018 are $(23) million for Southern Company and Southern Power. 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 June 30, 2017 As of December 31, 2016 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/Liabilities from risk management activities, net of collateral $ 23 $ 35 $ 73 $ 27 Other deferred charges and assets/Other deferred credits and liabilities 8 31 25 33 Total derivatives designated as hedging instruments for regulatory purposes $ 31 $ 66 $ 98 $ 60 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Liabilities from risk management activities, net of collateral $ 13 $ 10 $ 23 $ 7 Interest rate derivatives: Other current assets/Liabilities from risk management activities, net of collateral 11 1 12 1 Other deferred charges and assets/Other deferred credits and liabilities — 22 1 28 Foreign currency derivatives: Other current assets/Liabilities from risk management activities, net of collateral — 23 — 25 Other deferred charges and assets/Other deferred credits and liabilities 56 — — 33 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 80 $ 56 $ 36 $ 94 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Liabilities from risk management activities, net of collateral $ 237 $ 202 $ 489 $ 483 Other deferred charges and assets/Other deferred credits and liabilities 102 86 66 81 Interest rate derivatives: Other current assets/Liabilities from risk management activities, net of collateral — — 1 — Total derivatives not designated as hedging instruments $ 339 $ 288 $ 556 $ 564 Gross amounts recognized $ 450 $ 410 $ 690 $ 718 Gross amounts offset (*) $ (219 ) $ (290 ) $ (462 ) $ (524 ) Net amounts recognized in the Balance Sheets $ 231 $ 120 $ 228 $ 194 As of June 30, 2017 As of December 31, 2016 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/Liabilities from risk management activities $ 7 $ 7 $ 13 $ 5 Other deferred charges and assets/Other deferred credits and liabilities 2 4 7 4 Total derivatives designated as hedging instruments for regulatory purposes $ 9 $ 11 $ 20 $ 9 Gross amounts recognized $ 9 $ 11 $ 20 $ 9 Gross amounts offset $ (6 ) $ (6 ) $ (8 ) $ (8 ) Net amounts recognized in the Balance Sheets $ 3 $ 5 $ 12 $ 1 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 10 $ 4 $ 30 $ 1 Other deferred charges and assets/Other deferred credits and liabilities 5 10 14 7 Total derivatives designated as hedging instruments for regulatory purposes $ 15 $ 14 $ 44 $ 8 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ 1 $ 1 $ 2 $ — Other deferred charges and assets/Other deferred credits and liabilities — 2 — 3 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 1 $ 3 $ 2 $ 3 Gross amounts recognized $ 16 $ 17 $ 46 $ 11 Gross amounts offset $ (9 ) $ (9 ) $ (8 ) $ (8 ) Net amounts recognized in the Balance Sheets $ 7 $ 8 $ 38 $ 3 Gulf Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Liabilities from risk management activities $ 1 $ 16 $ 4 $ 12 Other deferred charges and assets/Other deferred credits and liabilities — 13 1 17 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 29 $ 5 $ 29 Gross amounts recognized $ 1 $ 29 $ 5 $ 29 Gross amounts offset $ (1 ) $ (1 ) $ (4 ) $ (4 ) Net amounts recognized in the Balance Sheets $ — $ 28 $ 1 $ 25 As of June 30, 2017 As of December 31, 2016 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Mississippi Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 6 $ 2 $ 6 Other deferred charges and assets/Other deferred credits and liabilities 1 4 2 5 Total derivatives designated as hedging instruments for regulatory purposes $ 2 $ 10 $ 4 $ 11 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ 3 $ — $ 2 $ — Other deferred charges and assets/Other deferred credits and liabilities — — 1 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 3 $ — $ 3 $ — Gross amounts recognized $ 5 $ 10 $ 7 $ 11 Gross amounts offset $ (2 ) $ (2 ) $ (3 ) $ (3 ) Net amounts recognized in the Balance Sheets $ 3 $ 8 $ 4 $ 8 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 13 $ 8 $ 18 $ 4 Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 25 Other deferred charges and assets/Other deferred credits and liabilities 56 — — 33 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 69 $ 31 $ 18 $ 62 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 1 $ 3 $ 1 Interest rate derivatives: Other current assets/Other current liabilities — — 1 — Total derivatives not designated as hedging instruments $ 1 $ 1 $ 4 $ 1 Gross amounts recognized $ 70 $ 32 $ 22 $ 63 Gross amounts offset $ (2 ) $ (2 ) $ (5 ) $ (5 ) Net amounts recognized in the Balance Sheets $ 68 $ 30 $ 17 $ 58 As of June 30, 2017 As of December 31, 2016 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 $ 4 $ 2 $ 24 $ 3 Other deferred charges and assets/Other deferred credits and liabilities — — 1 — Total derivatives designated as hedging instruments for regulatory purposes $ 4 $ 2 $ 25 $ 3 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 $ — $ 2 $ 4 $ 3 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 236 $ 201 $ 486 $ 482 Other deferred charges and assets/Other deferred credits and liabilities 102 86 66 81 Total derivatives not designated as hedging instruments $ 338 $ 287 $ 552 $ 563 Gross amounts of recognized $ 342 $ 291 $ 581 $ 569 Gross amounts offset (*) $ (196 ) $ (267 ) $ (435 ) $ (497 ) Net amounts recognized in the Balance Sheets $ 146 $ 24 $ 146 $ 72 (*) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $71 million and $62 million as of June 30, 2017 and December 31, 2016 , respectively. At June 30, 2017 and December 31, 2016 , 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 June 30, 2017 Derivative Category and Balance Sheet Location Southern Company (b) Alabama Power Georgia Power Gulf Power Mississippi Power Southern Company Gas (b) (in millions) Energy-related derivatives: Other regulatory assets, current $ (24 ) $ (3 ) $ — $ (15 ) $ (5 ) $ (1 ) Other regulatory assets, deferred (23 ) (2 ) (5 ) (13 ) (3 ) — Other regulatory liabilities, current (a) 13 3 6 — — 4 Total energy-related derivative gains (losses) $ (34 ) $ (2 ) $ 1 $ (28 ) $ (8 ) $ 3 (a) Georgia Power includes other regulatory liabilities, current in other current liabilities. (b) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $ 1 million at June 30, 2017 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2016 Derivative Category and Balance Sheet Location Southern Company (c) Alabama Power Georgia Power Gulf Power Mississippi Power Southern Company Gas (c) (in millions) Energy-related derivatives: Other regulatory assets, current $ (16 ) $ (1 ) $ — $ (9 ) $ (5 ) $ (1 ) Other regulatory assets, deferred (19 ) — — (16 ) (3 ) — Other regulatory liabilities, current (a) 56 8 29 1 1 17 Other regulatory liabilities, deferred (b) 12 4 7 — — 1 Total energy-related derivative gains (losses) $ 33 $ 11 $ 36 $ (24 ) $ (7 ) $ 17 (a) Georgia Power includes other regulatory liabilities, current in other current liabilities. (b) Georgia Power includes other regulatory liabilities, deferred in other deferred credits and liabilities. (c) 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 December 31, 2016 . For the three months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives, interest rate derivatives, and foreign currency derivatives designated as cash flow hedging instruments were as follows: Derivatives in Cash Flow Hedging Relationships Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Statements of Income Location Amount 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy-related derivatives $ (9 ) $ — Depreciation and amortization $ (2 ) $ — Interest rate derivatives (1 ) 6 Interest expense, net of amounts capitalized (5 ) (4 ) Foreign currency derivatives 71 (39 ) Interest expense, net of amounts capitalized (5 ) (1 ) Other income (expense), net (*) 79 (20 ) Total $ 61 $ (33 ) $ 67 $ (25 ) Alabama Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (2 ) $ (2 ) Georgia Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (1 ) $ (1 ) Gulf Power Interest rate derivatives $ (1 ) $ (2 ) Interest expense, net of amounts capitalized $ — $ — Southern Power Energy-related derivatives $ (7 ) $ — Depreciation and amortization $ (2 ) $ — Foreign currency derivatives 71 (39 ) Interest expense, net of amounts capitalized (5 ) (1 ) Other income (expense), net (*) 79 (20 ) Total $ 64 $ (39 ) $ 72 $ (21 ) (*) 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 Southern Company Gas, the pre-tax effect of energy related derivatives and interest rate derivatives designated as cash flow hedging instruments recognized in OCI and those reclassified from accumulated OCI into earnings for the successor three months ended June 30, 2017 and the predecessor three months ended June 30, 2016 were as follows: Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Successor Predecessor Successor Predecessor Derivatives in Cash Flow Hedging Relationships Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Statements of Income Location Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Energy-related derivatives $ (2 ) $ — Cost of natural gas $ — $ (1 ) Interest rate derivatives — (19 ) Interest expense, net of amounts capitalized — (1 ) Total $ (2 ) $ (19 ) $ — $ (2 ) For the six months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives, interest rate derivatives, and foreign currency derivatives designated as cash flow hedging instruments were as follows: Derivatives in Cash Flow Gain (Loss) Gain (Loss) Reclassified from Accumulated OCI into Statements of Income Location Amount 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy-related derivatives $ (20 ) $ — Depreciation and amortization $ (6 ) $ — Interest rate derivatives (1 ) (184 ) Interest expense, net of amounts capitalized (10 ) (7 ) Foreign currency derivatives 67 (39 ) Interest expense, net of amounts capitalized (12 ) (1 ) Other income (expense), net (*) 96 (20 ) Total $ 46 $ (223 ) $ 68 $ (28 ) Alabama Power Interest rate derivatives $ — $ (4 ) Interest expense, net of amounts capitalized $ (3 ) $ (3 ) Georgia Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (3 ) $ (2 ) Gulf Power Energy-related derivatives $ (1 ) $ — Depreciation and amortization $ — $ — Interest rate derivatives (1 ) (7 ) Interest expense, net of amounts capitalized — — Total $ (2 ) $ (7 ) $ — $ — Mississippi Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (1 ) $ (1 ) Southern Power Energy-related derivatives $ (15 ) $ — Depreciation and amortization $ (6 ) $ — Interest rate derivatives — — Interest expense, net of amounts capitalized — (1 ) Foreign currency derivatives 67 (39 ) Interest expense, net of amounts capitalized (12 ) (1 ) Other income (expense), net (*) 96 (20 ) Total $ 52 $ (39 ) $ 78 $ (22 ) (*) 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 Southern Company Gas, the pre-tax effect of energy related derivatives and interest rate derivatives designated as cash flow hedging instruments recognized in OCI and those reclassified from accumulated OCI into earnings for the successor six months ended June 30, 2017 and the predecessor six months ended June 30, 2016 were as follows: Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Successor Predecessor Successor Predecessor Derivatives in Cash Flow Hedging Relationships Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Statements of Income Location Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Energy-related derivatives $ (4 ) $ — Cost of natural gas $ — $ (1 ) Interest rate derivatives — (64 ) Interest expense, net of amounts capitalized — — Total $ (4 ) $ (64 ) $ — $ (1 ) For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives and interest rate derivatives designated as cash flow hedging instruments were immaterial for the other registrants. For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives and interest rate derivatives not designated as hedging instruments on the statements of income were as follows: Gain (Loss) Three Months Ended Six Months Ended Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy Related derivatives: Natural gas revenues (*) $ 16 $ — $ 65 $ — Cost of natural gas (2 ) — (4 ) — Total derivatives in non-designated hedging relationships $ 14 $ — $ 61 $ — (*) Excludes gains (losses) recorded in cost of natural gas associated with weather derivatives of $1 million and $15 million for the three and six months ended June 30, 2017 , respectively. Gain (Loss) Successor Predecessor Successor Predecessor Derivatives in Non-Designated Hedging Relationships Statements of Income Location Three Months Ended Three Months Ended Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Southern Company Gas Energy Related derivatives: Natural gas revenues (*) $ 16 $ (21 ) $ 65 $ (1 ) Cost of natural gas (2 ) (61 ) (4 ) (62 ) Total derivatives in non-designated hedging relationships $ 14 $ (82 ) $ 61 $ (63 ) (*) Excludes gains recorded in cost of natural gas associated with weather derivatives of $15 million for the successor six months ended June 30, 2017 and immaterial amounts for all other periods presented. For the three and six months ended June 30, 2017 and 2016 , 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. For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of interest rate derivatives designated as fair value hedging instruments were as follows: Derivatives in Fair Value Hedging Relationships Gain (Loss) Three Months Ended June 30, Six Months Ended June 30, Derivative Category Statements of Income Location 2017 2016 2017 2016 (in millions) (in millions) Southern Company Interest rate derivatives: Interest expense, net of amounts capitalized $ 7 $ 4 $ (1 ) $ 24 Georgia Power Interest rate derivatives: Interest expense, net of amounts capitalized $ — $ — $ (1 ) $ 15 For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of interest rate derivatives designated as fair value hedging instruments were offset by changes to the carrying value of long-term debt. There was no material ineffectiveness recorded in earnings for any registrant for any period presented. 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 June 30, 2017 , the registrants had no collateral posted with derivative counterparties to satisfy these arrangements. At June 30, 2017 , the fair value of derivative liabilities with contingent features was immaterial for all registrants. The maximum potential collateral requirements arising from the credit-risk-related contingent features, at a rating below BBB- and/or Baa3, were $11 million for Southern Company, $10 million for the traditional electric operating companies and Southern Power, and $1 million for Southern Company Gas. 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. 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 June 30, 2017 , 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 June 30, 2017 , cash collateral held on deposit in broker margin accounts was $71 million . Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas are exposed to losses related to financial instruments in the event of counterparties' nonperformance. Southern Company, the traditional electric operating companies, Southern Power, and Southern Company Gas only enter into agreements and material transactions with counterparties that have investment grade credit ratings by Moody's a

Acquisitions

Acquisitions	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS Southern Company Merger with Southern Company Gas Southern Company Gas is an energy services holding company whose primary business is the distribution of natural gas through the natural gas distribution utilities. On July 1, 2016, Southern Company completed the Merger for a total purchase price of approximately $8.0 billion and Southern Company Gas became a wholly-owned, direct subsidiary of Southern Company. The Merger was accounted for using the acquisition method of accounting with the assets acquired and liabilities assumed recognized at fair value as of the acquisition date. The following table presents the final purchase price allocation: Southern Company Gas Purchase Price (in millions) Current assets $ 1,557 Property, plant, and equipment 10,108 Goodwill 5,967 Intangible assets 400 Regulatory assets 1,118 Other assets 229 Current liabilities (2,201 ) Other liabilities (4,742 ) Long-term debt (4,261 ) Noncontrolling interest (174 ) Total purchase price $ 8,001 The excess of the purchase price over the estimated fair values of the assets acquired and liabilities assumed of $6.0 billion is recognized as goodwill, which is primarily attributable to positioning the Southern Company system to provide natural gas infrastructure to meet customers' growing energy needs and to compete for growth across the energy value chain. Southern Company anticipates that much of the value assigned to goodwill will not be deductible for tax purposes. The valuation of identifiable intangible assets included customer relationships, trade names, and storage and transportation contracts with estimated lives of one to 28 years . The estimated fair value measurements of identifiable intangible assets were primarily based on significant unobservable inputs (Level 3). The results of operations for Southern Company Gas have been included in Southern Company's consolidated financial statements from the date of acquisition and consist of operating revenues of $716 million and $2.3 billion and net income of $49 million and $288 million for the three and six months ended June 30, 2017 , respectively. The following summarized unaudited pro forma consolidated statement of earnings information assumes that the acquisition of Southern Company Gas was completed on January 1, 2015. The summarized unaudited pro forma consolidated statement of earnings information includes adjustments for (i) intercompany sales, (ii) amortization of intangible assets, (iii) adjustments to interest expense to reflect current interest rates on Southern Company Gas debt and additional interest expense associated with borrowings by Southern Company to fund the Merger, and (iv) the elimination of nonrecurring expenses associated with the Merger. For the Six Months Ended June 30, 2016 Operating revenues (in millions) $ 10,346 Net income attributable to Southern Company (in millions) $ 1,255 Basic Earnings Per Share (EPS) $ 1.34 Diluted EPS $ 1.33 These unaudited pro forma results are for comparative purposes only and may not be indicative of the results that would have occurred had this acquisition been completed on January 1, 2015 or the results that would be attained in the future. Acquisition of PowerSecure On May 9, 2016, Southern Company acquired all of the outstanding stock of PowerSecure, a provider of products and services in the areas of distributed generation, energy efficiency, and utility infrastructure, for $18.75 per common share in cash, resulting in an aggregate purchase price of $429 million . As a result, PowerSecure became a wholly-owned subsidiary of Southern Company. The acquisition of PowerSecure was accounted for using the acquisition method of accounting with the assets acquired and liabilities assumed recognized at fair value as of the acquisition date. The following table presents the final purchase price allocation: PowerSecure Purchase Price (in millions) Current assets $ 172 Property, plant, and equipment 46 Intangible assets 106 Goodwill 284 Other assets 4 Current liabilities (121 ) Long-term debt, including current portion (48 ) Deferred credits and other liabilities (14 ) Total purchase price $ 429 The excess of the purchase price over the estimated fair values of the assets acquired and liabilities assumed of $284 million was recognized as goodwill, which is primarily attributable to expected business expansion opportunities for PowerSecure. Southern Company anticipates that the majority of the value assigned to goodwill will not be deductible for tax purposes. The valuation of identifiable intangible assets included customer relationships, trade names, patents, backlog, and software with estimated lives of one to 26 years. The estimated fair value measurements of identifiable intangible assets were primarily based on significant unobservable inputs (Level 3). The results of operations for PowerSecure have been included in Southern Company's consolidated financial statements from the date of acquisition and are immaterial to the consolidated financial results of Southern Company. Pro forma results of operations have not been presented for the acquisition because the effects of the acquisition were immaterial to Southern Company's consolidated financial results for all periods presented. Southern Power See Note 2 to the financial statements of Southern Power and Note 12 to the financial statements of Southern Company under "Southern Power" in Item 8 of the Form 10-K for additional information. Acquisitions During the Six Months Ended June 30, 2017 During the six months ended June 30, 2017, in accordance with Southern Power's overall growth strategy, Southern Renewable Partnerships, LLC (SRP), one of Southern Power's wholly-owned subsidiaries, acquired the Bethel wind facility . Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller; Acquisition Date Approximate Nameplate Capacity ( MW ) Location Southern Power Percentage Ownership Actual COD PPA Contract Period Bethel Wind Invenergy, 276 Castro County, TX 100 % January 2017 12 years The aggregate amounts of revenue and net income, excluding impacts from PTCs, recognized by Southern Power related to the Bethel facility included in Southern Power's condensed consolidated statements of income for year-to-date 2017 were immaterial . The Bethel facility did not have operating revenues or activities prior to completion of construction and the assets being placed in service; therefore, supplemental pro forma information for the comparable 2016 period is not meaningful and has been omitted. In connection with Southern Power's 2016 acquisitions, allocations of the purchase price to individual assets were finalized during the six months ended June 30, 2017 with no changes to amounts originally reported for Boulder 1, Grant Plains, Grant Wind, Henrietta, Mankato, Passadumkeag, Salt Fork, Tyler Bluff, and Wake Wind. Acquisitions Subsequent to June 30, 2017 Subsequent to June 30, 2017, Southern Power acquired a 100% ownership interest in and commenced construction of the Cactus Flats 148 -MW wind facility, the majority of which is covered by two PPAs, which expire in 2030 and 2033. The facility is expected to be placed in service in mid-2018. The ultimate outcome of this matter cannot be determined at this time. Construction Projects Completed and in Progress During the six months ended June 30, 2017 , in accordance with its overall growth strategy, Southern Power completed construction of and placed in service, or continued construction of, the projects set forth in the following table. Through June 30, 2017 , total costs of construction incurred for these projects were $421 million , of which $49 million remained in CWIP for the Mankato facility acquired in 2016. Total aggregate construction costs, excluding the acquisition costs, are expected to be $170 million to $190 million for the Mankato facility. The ultimate outcome of this matter cannot be determined at this time. Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Six Months Ended June 30, 2017 East Pecos Solar 120 Pecos County, TX March 2017 15 years Lamesa Solar 102 Dawson County, TX April 2017 15 years Project Under Construction as of June 30, 2017 Mankato Natural Gas 345 Mankato, MN Second quarter 2019 20 years Development Projects In December 2016, as part of Southern Power's renewable development strategy, SRP entered into a joint development agreement with Renewable Energy Systems Americas, Inc. to develop and construct approximately 3,000 MWs of wind projects. Also in December 2016, Southern Power signed agreements and made payments to purchase wind turbine equipment from Siemens Wind Power, Inc. and Vestas-American Wind Technology, Inc. to be used for construction of the facilities. All of the wind turbine equipment was delivered by April 2017, which allows the projects to qualify for 100% PTCs for 10 years following their expected commercial operation dates between 2018 and 2020. The ultimate outcome of these matters cannot be determined at this time.

Joint Ownership Agreements

Joint Ownership Agreements	6 Months Ended
	Jun. 30, 2017
Regulated Operations [Abstract]
JOINT OWNERSHIP AGREEMENTS	JOINT OWNERSHIP AGREEMENTS Southern Company Gas See Note 4 to the financial statements of Southern Company Gas in Item 8 of the Form 10-K for additional information. Equity Method Investments The carrying amounts of Southern Company Gas' equity method investments as of June 30, 2017 and December 31, 2016 and related income from those investments for the successor three and six month periods ended June 30, 2017 and the predecessor three and six month periods ended June 30, 2016 were as follows: Balance Sheet Information June 30, 2017 December 31, 2016 (in millions) SNG $ 1,405 $ 1,394 Atlantic Coast Pipeline 53 33 PennEast Pipeline 45 22 Triton 43 44 Pivotal JAX LNG, LLC 32 16 Horizon Pipeline 31 30 Other 1 2 Total $ 1,610 $ 1,541 Successor Predecessor Successor Predecessor Income Statement Information Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) SNG $ 24 $ — $ 58 $ — Triton 2 1 2 1 PennEast Pipeline 1 — 4 — Atlantic Coast Pipeline 2 — 3 — Horizon Pipeline — — 1 1 Total $ 29 $ 1 $ 68 $ 2 Southern Natural Gas In September 2016, Southern Company Gas, through a wholly-owned, indirect subsidiary, acquired a 50% equity interest in SNG, which is accounted for as an equity method investment. On March 31, 2017, Southern Company Gas made an additional $50 million contribution to maintain its 50% equity interest in SNG. See Note 11 to the financial statements of Southern Company Gas under "Investment in SNG" in Item 8 of the Form 10-K for additional information on this investment. Selected financial information of SNG for the three and six months ended June 30, 2017 is as follows: Income Statement Information Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 (in millions) Revenues $ 143 $ 298 Operating income $ 63 $ 147 Net income $ 48 $ 114

Segment and Related Information

Segment and Related Information	6 Months Ended
	Jun. 30, 2017
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 four traditional electric operating companies – Alabama Power, Georgia Power, Gulf Power, and Mississippi Power – are vertically integrated utilities providing electric service in four Southeastern states. Southern Power 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 the seven natural gas distribution utilities in seven states and is involved in several other complementary businesses including gas marketing services, wholesale gas services, and gas midstream operations. Southern Company's reportable business segments are the sale of electricity by the four 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 $90 million and $190 million for the three and six months ended June 30, 2017 , respectively, and $107 million and $204 million for the three and six months ended June 30, 2016 , 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 technologies and services to electric utilities and large industrial, commercial, institutional, and municipal 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 six months ended June 30, 2017 and 2016 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 Operating revenues $ 4,157 $ 529 $ (101 ) $ 4,585 $ 716 $ 166 $ (37 ) $ 5,430 Segment net income (loss) (a)(b) (1,442 ) 82 — (1,360 ) 49 (68 ) (2 ) (1,381 ) Six Months Ended Operating revenues $ 7,943 $ 979 $ (206 ) $ 8,716 $ 2,276 $ 289 $ (79 ) $ 11,202 Segment net income (loss) (a)(b)(c) (1,010 ) 151 — (859 ) 288 (152 ) — (723 ) Total assets at June 30, 2017 $ 71,503 $ 14,703 $ (317 ) $ 85,889 $ 21,809 $ 2,348 $ (1,362 ) $ 108,684 Three Months Ended Operating revenues $ 4,115 $ 373 $ (109 ) $ 4,379 $ — $ 125 $ (45 ) $ 4,459 Segment net income (loss) (a)(b) 599 89 — 688 — (61 ) (4 ) 623 Six Months Ended Operating revenues $ 7,884 $ 688 $ (212 ) $ 8,360 $ — $ 172 $ (81 ) $ 8,451 Segment net income (loss) (a)(b) 1,064 139 — 1,203 — (84 ) (7 ) 1,112 Total assets at December 31, 2016 $ 72,141 $ 15,169 $ (316 ) $ 86,994 $ 21,853 $ 2,474 $ (1,624 ) $ 109,697 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes pre-tax charges for estimated probable losses on the Kemper IGCC of $3.0 billion ( $2.1 billion after tax) and $81 million ( $50 million after tax) for the three months ended June 30, 2017 and 2016 , respectively, and $3.1 billion ( $2.2 billion after tax) and $134 million ( $83 million after tax) for the six months ended June 30, 2017 and 2016 , respectively. See Note (B) under " Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate " for additional information. (c) Segment net income (loss) for the traditional electric operating companies also includes a pre-tax charge for the write-down of Gulf Power's ownership of Plant Scherer Unit 3 of $33 million ( $20 million after tax) for the six months ended June 30, 2017 . See Note (B) under " Regulatory Matters – Gulf Power – Retail Base Rate Cases " for additional information. Products and Services Electric Utilities' Revenues Period Retail Wholesale Other Total (in millions) Three Months Ended June 30, 2017 $ 3,777 $ 618 $ 190 $ 4,585 Three Months Ended June 30, 2016 3,748 446 185 4,379 Six Months Ended June 30, 2017 $ 7,171 $ 1,149 $ 396 $ 8,716 Six Months Ended June 30, 2016 7,124 842 394 8,360 Southern Company Gas' Revenues Period Gas Gas Other Total (in millions) Three Months Ended June 30, 2017 $ 557 $ 166 $ (7 ) $ 716 Six Months Ended June 30, 2017 $ 1,689 $ 454 $ 133 $ 2,276 Southern Company Gas Southern Company Gas manages its business through four reportable segments – gas distribution operations, gas marketing services, wholesale gas services, and gas midstream operations. 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 seven states. Gas marketing services includes natural gas marketing to end-use customers primarily in Georgia and Illinois. Additionally, gas marketing services provides home equipment protection products and services. 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 midstream operations primarily consists of Southern Company Gas' pipeline investments, with storage and fuel operations also aggregated into this segment. The all other column includes segments below the quantitative threshold for separate disclosure, including the subsidiaries that fall below the quantitative threshold for separate disclosure. After the Merger, Southern Company Gas changed its segment performance measure to net income. In order to properly assess net income by segment, Southern Company Gas executed various intercompany note agreements to revise interest charges to its segments. Since such agreements did not exist in the predecessor period, Southern Company Gas is unable to provide the comparable net income. Business segment financial data for the successor three and six months ended June 30, 2017 and the predecessor three and six months ended June 30, 2016 was as follows: Gas Distribution Operations Gas Marketing Services Wholesale Gas Services (*) Gas Midstream Operations Total All Other Eliminations Consolidated (in millions) Successor – Three Months Ended June 30, 2017: Operating revenues $ 603 $ 166 $ (12 ) $ 12 $ 769 $ 3 $ (56 ) $ 716 Segment net income 54 4 (17 ) 9 50 (1 ) — 49 Successor – Six Months Ended June 30, 2017: Operating revenues $ 1,783 $ 454 $ 119 $ 37 $ 2,393 $ 5 $ (122 ) $ 2,276 Segment net income 171 35 51 25 282 6 — 288 Successor – Total assets at $ 18,257 $ 2,093 $ 989 $ 2,381 $ 23,720 $ 11,182 $ (13,093 ) $ 21,809 Gas Distribution Operations Gas Marketing Services Wholesale Gas Services (*) Gas Midstream Operations Total All Other Eliminations Consolidated (in millions) Predecessor – Three Months Ended June 30, 2016: Operating revenues $ 547 $ 149 $ (95 ) $ 10 $ 611 $ 2 $ (42 ) $ 571 Segment EBIT 118 29 (112 ) (5 ) 30 (55 ) 1 (24 ) Predecessor – Six Months Ended June 30, 2016: Operating revenues $ 1,575 $ 435 $ (32 ) $ 25 $ 2,003 $ 4 $ (102 ) $ 1,905 Segment EBIT 353 109 (68 ) (6 ) 388 (60 ) — 328 Successor – Total assets at $ 19,453 $ 2,084 $ 1,127 $ 2,211 $ 24,875 $ 11,145 $ (14,167 ) $ 21,853 (*) 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) Successor – Three Months Ended June 30, 2017 $ 1,531 $ 123 $ 1,654 $ 1,666 $ (12 ) Successor – Six Months Ended June 30, 2017 3,370 259 3,629 3,510 119 Predecessor – Three Months Ended June 30 , 2016 $ 1,061 $ 58 $ 1,119 $ 1,214 $ (95 ) Predecessor – Six Months Ended June 30 , 2016 2,500 143 2,643 2,675 (32 )

Introduction (Policies)

Introduction (Policies)	6 Months Ended
	Jun. 30, 2017
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, 2016 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 June 30, 2017 and 2016 . 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. Southern Company's financial statements reflect its investments in its subsidiaries, including Southern Company Gas as a result of the Merger, on a consolidated basis. Southern Company Gas' results of operations and cash flows for the three and six months ended June 30, 2017 and financial condition as of June 30, 2017 and December 31, 2016 are reflected within Southern Company's consolidated amounts in these accompanying notes herein. The equity method is used for entities in which Southern Company has significant influence but does not control, including Southern Company Gas' investment in SNG, and for variable interest entities where Southern Company has an equity investment but is not the primary beneficiary. See Note (I) under " Southern Company – Merger with Southern Company Gas " for additional information regarding the Merger. Pursuant to the Merger, Southern Company pushed down the application of the acquisition method of accounting to the consolidated financial statements of Southern Company Gas such that the assets and liabilities are recorded at their respective fair values, and goodwill has been established for the excess of the purchase price over the fair value of net identifiable assets. Accordingly, the consolidated financial statements of Southern Company Gas for periods before and after July 1, 2016 (acquisition date) reflect different bases of accounting, and the financial positions and results of operations of those periods are not comparable. Throughout Southern Company Gas' condensed consolidated financial statements and the accompanying notes herein, periods prior to July 1, 2016 are identified as "predecessor," while periods after the acquisition date are identified as "successor."
Reclassification	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 Issued Accounting Standards	Recently Issued Accounting Standards In 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (ASC 606), replacing the existing accounting standard and industry specific guidance for revenue recognition with a five-step model for recognizing and measuring revenue from contracts with customers. The underlying principle of the standard is to recognize revenue to depict the transfer of goods or services to customers at the amount expected to be collected. The new standard also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and the related cash flows arising from contracts with customers. While the registrants expect most of their revenue to be included in the scope of ASC 606, they have not fully completed the evaluation of all revenue arrangements. The majority of Southern Company's, the traditional electric operating companies', and Southern Company Gas' revenue, including energy provided to customers, is from tariff offerings that provide electricity or natural gas without a defined contractual term, as well as longer-term contractual commitments , including PPAs and non-derivative natural gas asset management and optimization arrangements . The majority of Southern Power's revenues includes longer-term PPAs for generation capacity and energy. The registrants expect the adoption of ASC 606 will not result in a significant shift from the current timing of revenue recognition for such transactions . The registrants' ongoing evaluation of other revenue streams and related contracts includes unregulated sales to customers. Some revenue arrangements, such as certain PPAs , energy-related derivatives , and alternative revenue programs, are excluded from the scope of ASC 606 and, therefore, will be accounted for and disclosed or presented separately from revenues under ASC 606 on the registrants' financial statements. In addition, the power and utilities industry continues to evaluate other specific industry issues, including the applicability of ASC 606 to contributions in aid of construction (CIAC). Although final implementation guidance has not been issued, Southern Company, the traditional electric operating companies, and Southern Company Gas expect CIAC to be out of the scope of ASC 606. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017. The registrants intend to use the modified retrospective method of adoption effective January 1, 2018. The registrants have also elected to utilize practical expedients which allow them to apply the standard to open contracts at the date of adoption and to reflect the aggregate effect of all modifications when identifying performance obligations and allocating the transaction price for contracts modified before the effective date. Under the modified retrospective method of adoption, prior year reported results are not restated; however, a cumulative-effect adjustment to retained earnings at January 1, 2018 is recorded. In addition, disclosures will include comparative information on 2018 financial statement line items under current guidance. While the adoption of ASC 606, including the cumulative-effect adjustment, is not expected to have a material impact on either the timing or amount of revenues recognized in the registrants' financial statements, the registrants will continue to evaluate the requirements, as well as any additional clarifying guidance that may be issued. On January 26, 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to compare the implied fair value of goodwill with the carrying amount as part of Step 2 of the goodwill impairment test. Under the new standard, the goodwill impairment loss will be measured as the excess of a reporting unit's carrying amount over its fair value, not exceeding the total amount of goodwill allocated to that reporting unit, which may increase the frequency of goodwill impairment charges if a future goodwill impairment test does not pass the Step 1 evaluation. ASU 2017-04 is effective prospectively for annual and interim periods beginning on or after December 15, 2019, and early adoption is permitted on testing dates after January 1, 2017. On March 10, 2017, the FASB issued ASU No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (ASU 2017-07). ASU 2017-07 requires that an employer report the service cost component in the same line item or items as other compensation costs and requires the other components of net periodic pension and postretirement benefit costs to be separately presented in the income statement outside income from operations. Additionally, only the service cost component is eligible for capitalization, when applicable. However, all cost components remain eligible for capitalization under FERC regulations. ASU 2017-07 will be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension and postretirement benefit costs in the income statement. The capitalization of the service cost component of net periodic pension and postretirement benefit costs in assets will be applied on a prospective basis. ASU 2017-07 is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Southern Company, the traditional electric operating companies, and Southern Company Gas are currently evaluating the new standard. The presentation changes required for net periodic pension and postretirement benefit costs will result in a decrease in Southern Company's , the traditional electric operating companies', and Southern Company Gas' operating income and an increase in other income for 2016 and 2017 and are expected to result in a decrease in operating income and an increase in other income for 2018. The adoption of ASU 2017-07 is not expected to have a material impact on Southern Company's , the traditional electric operating companies', or Southern Company Gas' financial statements.
Affiliate Transactions	Affiliate Transactions Prior to the completion of Southern Company Gas' acquisition of its 50% equity interest in SNG, SCS (as agent for Alabama Power, Georgia Power, and Southern Power) and Southern Company Gas had entered into long-term interstate natural gas transportation agreements with SNG. The interstate transportation service provided to Alabama Power, Georgia Power, Southern Power, and Southern Company Gas by SNG pursuant to these agreements is governed by the terms and conditions of SNG's natural gas tariff and is subject to FERC regulation. For the six months ended June 30, 2017 , transportation costs under these agreements for Alabama Power, Georgia Power, Southern Power, and Southern Company Gas were approximately $4 million , $51 million , $13 million , and $16 million , respectively. SCS, as agent for Georgia Power and Southern Power, has agreements with certain subsidiaries of Southern Company Gas to purchase natural gas. For the six months ended June 30, 2017 , natural gas purchases made by Georgia Power and Southern Power from Southern Company Gas' subsidiaries were approximately $9 million and $56 million , respectively.
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.
Property Damage Reserve	Property Damage Reserve See Note 1 to the financial statements of Gulf Power under "Property Damage Reserve" in Item 8 of the Form 10-K for additional information. Gulf Power's cost of repairing damages from major storms and other uninsured property damages, including uninsured damages to transmission and distribution facilities, generation facilities, and other property is charged to Gulf Power's property damage reserve. In accordance with a settlement agreement approved by the Florida PSC on April 4, 2017 (2017 Rate Case Settlement Agreement), Gulf Power suspended further property damage reserve accruals effective April 2017. Gulf Power may make discretionary accruals, but is required to resume accruals of $3.5 million annually if the reserve balance falls below zero . In addition, Gulf Power may initiate a storm surcharge to recover costs associated with any tropical systems named by the National Hurricane Center or other catastrophic storm events that reduce the property damage reserve in the aggregate by approximately $31 million ( 75% of the April 1, 2017 balance) or more. The storm surcharge would begin, on an interim basis, 60 days following the filing of a cost recovery petition, would be limited to $4.00 /month for a 1,000 KWH residential customer unless Gulf Power incurs in excess of $100 million in qualified storm recovery costs in a calendar year, and would replenish the storm reserve to approximately $40 million . See Note (B) under " Regulatory Matters – Gulf Power – Retail Base Rate Cases " for additional details regarding the 2017 Rate Case Settlement Agreement.
Natural Gas For Sale	Natural Gas for Sale Southern Company Gas' natural gas distribution utilities, with the exception of Nicor Gas, carry natural gas inventory on a WACOG basis. Nicor Gas' natural gas inventory is carried at cost on a LIFO basis. Inventory decrements occurring during the year that are restored prior to year end are charged to cost of natural gas at the estimated annual replacement cost. Inventory decrements that are not restored prior to year end are charged to cost of natural gas at the actual LIFO cost of the inventory layers liquidated. Southern Company Gas' inventory decrement at June 30, 2017 is expected to be restored prior to year end. The cost of natural gas, including inventory costs, is recovered from customers under a purchased gas recovery mechanism adjusted for differences between actual costs and amounts billed; therefore, LIFO liquidations have no impact on Southern Company's or Southern Company Gas' net income. Natural gas inventories for Southern Company Gas' non-utility businesses are carried at the lower of weighted average cost or current market price, with cost determined on a WACOG basis. For any declines in market prices below the WACOG considered to be other than temporary, an adjustment is recorded to reduce the value of natural gas inventories to market value. Southern Company Gas had no material LOCOM adjustment in any period presented.
Valuation Methodologies	Valuation Methodologies The energy-related derivatives primarily consist of exchange-traded and over-the-counter financial products for natural gas and physical power products, including, from time to time, basis swaps. These are standard products used within the energy industry and are valued using the market approach. The inputs used are mainly from observable market sources, such as forward natural gas prices, power prices, implied volatility, and overnight index swap interest rates. Interest rate derivatives are also standard over-the-counter products that are valued using observable market data and assumptions commonly used by market participants. The fair value of interest rate derivatives reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future interest rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and occasionally, implied volatility of interest rate options. The fair value of cross-currency swaps reflects the net present value of expected payments and receipts under the swap agreement based on the market's expectation of future foreign currency exchange rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and discount rates. The interest rate derivatives and cross-currency swaps are categorized as Level 2 under Fair Value Measurements as these inputs are based on observable data and valuations of similar instruments. See Note (H) for additional information on how these derivatives are used. The NRC requires licensees of commissioned nuclear power reactors to establish a plan for providing reasonable assurance of funds for future decommissioning. For fair value measurements of the investments within the nuclear decommissioning 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. See Note 1 to the financial statements of Southern Company, Alabama Power, and Georgia Power 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 obligated to make generation-based payments to the seller over a period ranging from 10 to 30 years, beginning at the commercial operation date. 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, and is evaluated periodically. The fair value of contingent consideration reflects the net present value of expected payments and any periodic change arising from forecasted generation is expected to be immaterial. "Other investments" include investments that are not traded in the open market. The fair value of these investments has been determined based on market factors including comparable multiples and the expectations regarding cash flows and business plan executions.
Earnings per Share	Earnings per Share For Southern Company, the only difference in computing basic and diluted earnings per share is attributable to awards outstanding under the stock option and performance share plans. See Note 8 to the financial statements of Southern Company in Item 8 of the Form 10-K for information on the stock option and performance share plans. The effect of both stock options and performance share award units was determined using the treasury stock method.
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 (C) for additional information. In the statements of cash flows, the cash impacts of settled energy-related and interest rate derivatives are recorded as operating activities. The 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. Energy-Related Derivatives Southern Company, 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 is expected to continue to mitigate price volatility. The Florida PSC extended the moratorium on Gulf Power's fuel-hedging program through January 1, 2021 in connection with the 2017 Rate Case Settlement Agreement. The moratorium does not have an impact on the recovery of existing hedges entered into under the previously-approved hedging program. 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 the statements of income. Energy-related derivative contracts are accounted for under one of three methods: • Regulatory Hedges — Energy-related derivative contracts which are 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 OCI before being recognized in the statements of income in the same period as the hedged transactions are reflected in earnings. • Not Designated — Gains and losses on energy-related derivative contracts that are not designated or fail to qualify as hedges are recognized in the statements of income as incurred. Some energy-related derivative contracts require physical delivery as opposed to financial settlement, and this type of derivative is both common and prevalent within the electric and natural gas industries. When an energy-related derivative contract is settled physically, any cumulative unrealized gain or loss is reversed and the contract price is recognized in the respective line item representing the actual price of the underlying goods being delivered. Interest Rate Derivatives Southern Company and certain subsidiaries may also 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 effective portion of the derivatives' fair value gains or losses is recorded in OCI and is reclassified into earnings at the same time the hedged transactions affect earnings, with any ineffectiveness recorded directly to earnings. 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, providing an offset, with any difference representing ineffectiveness. 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.

Introduction (Tables)

Introduction (Tables)	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Goodwill	At June 30, 2017 and December 31, 2016, goodwill was as follows: Goodwill At June 30, 2017 At December 31, 2016 (in millions) Southern Company $ 6,271 $ 6,251 Southern Power $ 2 $ 2 Southern Company Gas Gas distribution operations $ 4,702 $ 4,702 Gas marketing services 1,265 1,265 Southern Company Gas total $ 5,967 $ 5,967
Schedule of Goodwill and Other Intangible Assets	Other intangible assets were as follows: At June 30, 2017 At December 31, 2016 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 $ 288 $ (57 ) $ 231 $ 268 $ (32 ) $ 236 Trade names 159 (11 ) 148 158 (5 ) 153 Patents 4 — 4 4 — 4 Backlog 5 (1 ) 4 5 (1 ) 4 Storage and transportation contracts 64 (21 ) 43 64 (2 ) 62 Software and other 4 (1 ) 3 2 — 2 PPA fair value adjustments 456 (35 ) 421 456 (22 ) 434 Total other intangible assets subject to amortization $ 980 $ (126 ) $ 854 $ 957 $ (62 ) $ 895 Other intangible assets not subject to amortization: Federal Communications Commission licenses $ 75 $ — $ 75 $ 75 $ — $ 75 Total other intangible assets $ 1,055 $ (126 ) $ 929 $ 1,032 $ (62 ) $ 970 Southern Power Other intangible assets subject to amortization: PPA fair value adjustments $ 456 $ (35 ) $ 421 $ 456 $ (22 ) $ 434 Southern Company Gas Other intangible assets subject to amortization: Gas marketing services Customer relationships $ 221 $ (53 ) $ 168 $ 221 $ (30 ) $ 191 Trade names 115 (6 ) 109 115 (2 ) 113 Wholesale gas services Storage and transportation contracts 64 (21 ) 43 64 (2 ) 62 Total other intangible assets subject to amortization $ 400 $ (80 ) $ 320 $ 400 $ (34 ) $ 366
Finite-lived Intangible Assets Amortization Expense	Amortization associated with other intangible assets was as follows: Three Months Ended Six Months Ended June 30, 2017 (in millions) Southern Company $ 29 $ 65 Southern Power $ 6 $ 13 Southern Company Gas $ 20 $ 46

Contingencies and Regulatory 23

Contingencies and Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Revised Cost and Schedule	Georgia Power's preliminary assessment results indicate that its proportionate share of the remaining estimated cost to complete Plant Vogtle Units 3 and 4 ranges as follows: Preliminary in-service dates Unit 3 February 2021 – March 2022 Unit 4 February 2022 – March 2023 (in billions) Preliminary estimated cost to complete $ 3.9 – $ 4.6 CWIP as of June 30, 2017 4.5 4.5 Guarantee Obligations (1.7 ) (1.7 ) Estimated capital costs $ 6.7 – $ 7.4 Vogtle Cost Settlement Agreement Revised Forecast (5.7 ) (5.7 ) Estimated net additional capital costs $ 1.0 – $ 1.7 Preliminary Cancellation Cost Estimate (in billions) CWIP as of June 30, 2017 $ 4.5 Financing costs collected, net of tax 1.4 Cancellation costs (*) 0.4 Total $ 6.3 (*) The estimate for cancellation costs includes, but is not limited to, costs to terminate contracts for construction and other services, as well as costs to secure the Plant Vogtle Units 3 and 4 construction site.
Recovery Balance of Each Regulatory Clause	The balance of each regulatory clause recovery on the balance sheet follows: Regulatory Clause Balance Sheet Line Item June 30, December 31, (in millions) Rate CNP Compliance (*) Deferred under recovered regulatory clause revenues $ 6 $ 9 Rate CNP PPA Over recovered regulatory clause revenues 1 — Deferred under recovered regulatory clause revenues — 142 Retail Energy Cost Recovery Other regulatory liabilities, current 11 76 Natural Disaster Reserve Other regulatory liabilities, deferred 56 69 (*) In accordance with an accounting order issued on February 17, 2017 by the Alabama PSC, Alabama Power reclassified $36 million of its under recovered balance for Rate CNP Compliance to a deferred regulatory asset account. The balance of each regulatory clause recovery on the balance sheet follows: Regulatory Clause Balance Sheet Line Item June 30, December 31, (in millions) Fuel Cost Recovery Under recovered regulatory clause revenues $ 7 $ — Fuel Cost Recovery Other regulatory liabilities, current — 15 Purchased Power Capacity Recovery Under recovered regulatory clause revenues 5 — Environmental Cost Recovery Under recovered regulatory clause revenues 12 13 Energy Conservation Cost Recovery Under recovered regulatory clause revenues 2 4
Current And Actual Cost Estimate	Mississippi Power's Kemper IGCC 2010 project estimate, cost estimate at the time of project suspension (which includes the impacts of the Mississippi Supreme Court's (Court) decision discussed herein under "Rate Recovery of Kemper IGCC Costs – 2013 MPSC Rate Order"), and actual costs incurred as of June 30, 2017 , all of which include 100% of the costs for the Kemper IGCC, are as follows: Cost Category 2010 Project Estimate (a) Cost Estimate at Suspension (b) June 30, 2017 Actual Costs (in billions) Plant Subject to Cost Cap (c)(e) $ 2.40 $ 5.95 $ 5.68 Lignite Mine and Equipment 0.21 0.23 0.23 CO 2 Pipeline Facilities 0.14 0.11 0.11 AFUDC (d) 0.17 0.85 0.85 Combined Cycle and Related Assets Placed in (e) — 0.05 0.05 General Exceptions 0.05 0.10 0.08 Deferred Costs (e) — 0.23 0.23 Additional DOE Grants (f) — (0.14 ) (0.14 ) Total Kemper IGCC $ 2.97 $ 7.38 $ 7.09 (a) Represents the certificated cost estimate adjusted to include the certificated estimate for the CO 2 pipeline facilities approved in 2011 by the Mississippi PSC, as well as the lignite mine and equipment, AFUDC, and general exceptions. (b) Represents actual costs through June 30, 2017 and projected costs at the time of project suspension, including estimated post-in-service costs which were expected to be subject to the cost cap. (c) The 2012 MPSC CPCN Order approved a construction cost cap of up to $2.88 billion , net of the Initial DOE Grants and excluding the cost of the lignite mine and equipment, the cost of the CO 2 pipeline facilities, AFUDC, and certain general exceptions, including change of law, force majeure, and beneficial capital (which exists when Mississippi Power demonstrates that the purpose and effect of the construction cost increase is to produce efficiencies that will result in a neutral or favorable effect on customers relative to the original proposal for the CPCN) (Cost Cap Exceptions). The Cost Estimate at Suspension and the Actual Costs include non-incremental operating and maintenance costs related to the combined cycle and associated common facilities placed in service in August 2014 that are subject to the $2.88 billion cost cap and exclude post-in-service costs for the lignite mine. See " Rate Recovery of Kemper IGCC Costs – 2013 MPSC Rate Order " herein for additional information. (d) Mississippi Power's 2010 Project Estimate included recovery of financing costs during construction rather than the accrual of AFUDC. This approach was not approved by the Mississippi PSC as described in " Rate Recovery of Kemper IGCC Costs – 2013 MPSC Rate Order ." The Cost Estimate at Suspension also reflects the impact of a settlement agreement with the wholesale customers for cost-based rates under FERC's jurisdiction. See " FERC Matters " herein for additional information. (e) Non-capital Kemper IGCC-related costs incurred during construction were initially deferred as regulatory assets. Some of these costs are included in current rates and are being recognized through income; however, such costs remained in the Cost Estimate at Suspension and are reflected in the Actual Costs at June 30, 2017 . The equity return associated with assets placed in service and other non-CWIP accounts deferred for regulatory purposes, as well as the wholesale portion of debt carrying costs, whether deferred or recognized through income, was not included in the Cost Estimate at Suspension or in the Actual Costs at June 30, 2017 . At June 30, 2017, such deferred amounts totaled $33 million and $1 million , respectively. (f) On April 8, 2016, Mississippi Power received approximately $137 million in additional grants from the DOE for the Kemper IGCC (Additional DOE Grants).

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	As of June 30, 2017 , 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 June 30, 2017: 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)(b) $ 193 $ 179 $ — $ — $ 372 Interest rate derivatives — 11 — — 11 Foreign currency derivatives — 56 — — 56 Nuclear decommissioning trusts (c) 728 966 — 25 1,719 Cash equivalents 834 — — — 834 Other investments 9 — 1 — 10 Total $ 1,764 $ 1,212 $ 1 $ 25 $ 3,002 Liabilities: Energy-related derivatives (a)(b) $ 205 $ 161 $ — $ — $ 366 Interest rate derivatives — 23 — — 23 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 20 — 20 Total $ 205 $ 207 $ 20 $ — $ 432 Alabama Power Assets: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Nuclear decommissioning trusts: (d) Domestic equity 411 79 — — 490 Foreign equity 56 54 — — 110 U.S. Treasury and government agency securities — 29 — — 29 Corporate bonds 22 145 — — 167 Mortgage and asset backed securities — 18 — — 18 Private Equity — — — 25 25 Other — 6 — — 6 Cash equivalents 493 — — — 493 Total $ 982 $ 340 $ — $ 25 $ 1,347 Liabilities: Energy-related derivatives $ — $ 11 $ — $ — $ 11 Fair Value Measurements Using: As of June 30, 2017: 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) Georgia Power Assets: Energy-related derivatives $ — $ 15 $ — $ — $ 15 Interest rate derivatives — 1 — — 1 Nuclear decommissioning trusts: (d) (e) Domestic equity 225 1 — — 226 Foreign equity — 147 — — 147 U.S. Treasury and government agency securities — 198 — — 198 Municipal bonds — 72 — — 72 Corporate bonds — 169 — — 169 Mortgage and asset backed securities — 41 — — 41 Other 14 7 — — 21 Cash equivalents 50 — — — 50 Total $ 289 $ 651 $ — $ — $ 940 Liabilities: Energy-related derivatives $ — $ 14 $ — $ — $ 14 Interest rate derivatives — 3 — — 3 Total $ — $ 17 $ — $ — $ 17 Gulf Power Assets: Energy-related derivatives $ — $ 1 $ — $ — $ 1 Cash equivalents 21 — — — 21 Total $ 21 $ 1 $ — $ — $ 22 Liabilities: Energy-related derivatives $ — $ 29 $ — $ — $ 29 Mississippi Power Assets: Energy-related derivatives $ — $ 2 $ — $ — $ 2 Interest rate derivatives — 3 — — 3 Cash equivalents 100 — — — 100 Total $ 100 $ 5 $ — $ — $ 105 Liabilities: Energy-related derivatives $ — $ 10 $ — $ — $ 10 Fair Value Measurements Using: As of June 30, 2017: 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 Power Assets: Energy-related derivatives $ — $ 14 $ — $ — $ 14 Foreign currency derivatives — 56 — — 56 Total $ — $ 70 $ — $ — $ 70 Liabilities: Energy-related derivatives $ — $ 9 $ — $ — $ 9 Foreign currency derivatives — 23 — — 23 Contingent consideration — — 20 — 20 Total $ — $ 32 $ 20 $ — $ 52 Southern Company Gas Assets: Energy-related derivatives (a)(b) $ 193 $ 138 $ — $ — $ 331 Liabilities: Energy-related derivatives (a)(b) $ 205 $ 86 $ — $ — $ 291 (a) Excludes $11 million associated with certain weather derivatives accounted for based on intrinsic value rather than fair value. (b) Excludes cash collateral of $71 million . (c) For additional detail, see the nuclear decommissioning trusts sections for Alabama Power and Georgia Power in this table. (d) Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. (e) Includes the investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. As of June 30, 2017 , approximately $38 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.
Fair value measurements of investments calculated at net asset value per share as well as the nature and risk of those investments	As of June 30, 2017 , the fair value measurements of private equity investments held in the nuclear decommissioning trust that are calculated at net asset value per share (or its equivalent) as a practical expedient, as well as the nature and risks of those investments, were as follows: As of June 30, 2017: Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period (in millions) Southern Company $ 25 $ 22 Not Applicable Not Applicable Alabama Power $ 25 $ 22 Not Applicable Not Applicable
Financial instruments for which carrying amount did not equal fair value	As of June 30, 2017 , other financial instruments for which the carrying amount did not equal fair value were as follows: Carrying Amount Fair Value (in millions) Long-term debt, including securities due within one year: Southern Company $ 46,631 $ 48,228 Alabama Power $ 7,440 $ 8,041 Georgia Power $ 10,888 $ 11,585 Gulf Power $ 1,292 $ 1,336 Mississippi Power $ 2,125 $ 2,071 Southern Power $ 5,725 $ 5,878 Southern Company Gas $ 5,699 $ 6,031

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Earnings per Share	Shares used to compute diluted earnings per share were as follows: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) As reported shares 998 934 996 925 Effect of options and performance share award units 7 6 7 6 Diluted shares 1,005 940 1,003 931
Changes in Stockholders' Equity	The following table presents year-to-date changes in stockholders' equity of Southern Company: Number of Common Shares Common Preferred and Preference Stock of Subsidiaries Total Issued Treasury Noncontrolling Interests (*) (in thousands) (in millions) Balance at December 31, 2016 991,213 (819 ) $ 24,758 $ 609 $ 1,245 $ 26,612 Consolidated net income (loss) attributable to Southern Company — — (723 ) — — (723 ) Other comprehensive income (loss) — — (11 ) — — (11 ) Stock issued 9,129 — 417 — — 417 Stock-based compensation — — 72 — — 72 Cash dividends on common stock — — (1,134 ) — — (1,134 ) Preference stock redemption — — — (150 ) — (150 ) Contributions from noncontrolling interests — — — 71 71 Distributions to noncontrolling interests — — — — (40 ) (40 ) Net income attributable to noncontrolling interests — — — — 16 16 Reclassification from redeemable noncontrolling interests — — — — 114 114 Other — (49 ) (7 ) 3 1 (3 ) Balance at June 30, 2017 1,000,342 (868 ) $ 23,372 $ 462 $ 1,407 $ 25,241 Balance at December 31, 2015 915,073 (3,352 ) $ 20,592 $ 609 $ 781 $ 21,982 Consolidated net income attributable to Southern Company — — 1,112 — — 1,112 Other comprehensive income (loss) — — (117 ) — — (117 ) Stock issued 27,297 2,599 1,383 — — 1,383 Stock-based compensation — — 67 — — 67 Cash dividends on common stock — — (1,023 ) — — (1,023 ) Contributions from noncontrolling interests — — — — 169 169 Distributions to noncontrolling interests — — — — (10 ) (10 ) Purchase of membership interests from noncontrolling interests — — — — (129 ) (129 ) Net income attributable to noncontrolling interests — — — — 11 11 Other — (19 ) 1 — — 1 Balance at June 30, 2016 942,370 (772 ) $ 22,015 $ 609 $ 822 $ 23,446 (*) Related to Southern Power Company and excludes redeemable noncontrolling interests. In April 2017, approximately $114 million was reclassified from redeemable noncontrolling interests to noncontrolling interests, included in stockholder's equity, due to the expiration of SunPower Corp's option to require Southern Power to purchase its membership interests in one of the solar partnerships. See Note 10 to the financial statements of Southern Power in Item 8 of the Form 10-K for additional information.

Financing (Tables)

Financing (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Credit arrangements by company	The following table outlines the committed credit arrangements by company as of June 30, 2017 : Expires Executable Term Loans Expires Within One Year Company 2017 2018 2019 2020 2022 Total Unused One Year Two Years Term Out No Term Out (in millions) Southern Company (a) $ — $ — $ — $ — $ 2,000 $ 2,000 $ 2,000 $ — $ — $ — $ — Alabama Power 3 532 — — 800 1,335 1,335 — — — 35 Georgia Power — — — — 1,750 1,750 1,732 — — — — Gulf Power 30 195 25 30 — 280 280 45 — — 40 Mississippi Power 113 — — — — 113 100 — 13 13 100 Southern Power Company — — — — 750 750 675 — — — — Southern Company Gas (b) — — — — 1,900 1,900 1,849 — — — — Other 10 30 — — — 40 40 20 — 20 20 Southern Company Consolidated $ 156 $ 757 $ 25 $ 30 $ 7,200 $ 8,168 $ 8,011 $ 65 $ 13 $ 33 $ 195 (a) Represents the Southern Company parent entity. (b) Southern Company Gas, as the parent entity, guarantees the obligations of Southern Company Gas Capital, which is the borrower of $1.2 billion of these arrangements. Southern Company Gas' committed credit arrangements also include $700 million for which Nicor Gas is the borrower and which is restricted for working capital needs of Nicor Gas.
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 six months of 2017 : Company Senior Note Issuances Senior Note Maturities and Redemptions Revenue Bond Other Long-Term Debt Issuances Other Long-Term Debt Redemptions and Maturities (a) (in millions) Southern Company (b) $ 300 $ — $ — $ 500 $ 400 Alabama Power 550 200 — — — Georgia Power 850 450 27 — 3 Gulf Power 300 85 — 6 — Mississippi Power — — — 40 893 Southern Power — — — 3 3 Southern Company Gas (c) 450 — — — — Other — — — — 8 Elimination (d) — — — (40 ) (591 ) Southern Company Consolidated $ 2,450 $ 735 $ 27 $ 509 $ 716 (a) Includes reductions in capital lease obligations resulting from cash payments under capital leases. (b) Represents the Southern Company parent entity. (c) The senior notes were issued by Southern Company Gas Capital and guaranteed by the Southern Company Gas parent entity. (d) Intercompany loans from Southern Company to Mississippi Power eliminated in Southern Company's Consolidated Financial Statements.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2017
Retirement Benefits [Abstract]
Pension Plans and Postretirement Plans	Components of the net periodic benefit costs for the three and six months ended June 30, 2017 and 2016 are presented in the following tables. Pension Plans Southern Company Alabama Power Georgia Power Gulf Power Mississippi Power (in millions) Three Months Ended June 30, 2017 Service cost $ 74 $ 16 $ 18 $ 4 $ 3 Interest cost 113 24 35 5 5 Expected return on plan assets (225 ) (49 ) (70 ) (9 ) (10 ) Amortization: Prior service costs 3 — 1 — 1 Net (gain)/loss 41 11 14 1 2 Net periodic pension cost (income) $ 6 $ 2 $ (2 ) $ 1 $ 1 Six Months Ended June 30, 2017 Service cost $ 147 $ 32 $ 37 $ 7 $ 7 Interest cost 227 48 69 10 10 Expected return on plan assets (449 ) (98 ) (141 ) (19 ) (20 ) Amortization: Prior service costs 6 1 2 — 1 Net (gain)/loss 81 21 28 3 4 Net periodic pension cost (income) $ 12 $ 4 $ (5 ) $ 1 $ 2 Three Months Ended June 30, 2016 Service cost $ 62 $ 15 $ 18 $ 3 $ 3 Interest cost 101 24 34 4 5 Expected return on plan assets (187 ) (46 ) (65 ) (8 ) (8 ) Amortization: Prior service costs 3 — 2 1 — Net (gain)/loss 37 10 13 1 1 Net periodic pension cost $ 16 $ 3 $ 2 $ 1 $ 1 Six Months Ended June 30, 2016 Service cost $ 124 $ 29 $ 35 $ 6 $ 6 Interest cost 201 48 68 9 10 Expected return on plan assets (374 ) (92 ) (129 ) (17 ) (17 ) Amortization: Prior service costs 7 1 3 1 — Net (gain)/loss 75 20 27 3 3 Net periodic pension cost $ 33 $ 6 $ 4 $ 2 $ 2 Pension Plans Southern Company Gas (in millions) Successor – Three Months Ended June 30, 2017 Service cost $ 5 Interest cost 10 Expected return on plan assets (17 ) Amortization: Prior service costs (1 ) Net (gain)/loss 5 Net periodic pension cost $ 2 Successor – Six Months Ended June 30, 2017 Service cost $ 11 Interest cost 20 Expected return on plan assets (35 ) Amortization: Prior service costs (1 ) Net (gain)/loss 10 Net periodic pension cost $ 5 Predecessor – Three Months Ended June 30, 2016 Service cost $ 7 Interest cost 11 Expected return on plan assets (17 ) Amortization: Prior service costs (1 ) Net (gain)/loss 7 Net periodic pension cost $ 7 Predecessor – Six Months Ended June 30, 2016 Service cost $ 13 Interest cost 21 Expected return on plan assets (33 ) Amortization: Prior service costs (1 ) Net (gain)/loss 13 Net periodic pension cost $ 13 Postretirement Benefits Southern Company Alabama Power Georgia Power Gulf Power Mississippi Power (in millions) Three Months Ended June 30, 2017 Service cost $ 6 $ 2 $ 1 $ 1 $ 1 Interest cost 20 4 8 — 1 Expected return on plan assets (17 ) (8 ) (6 ) (1 ) (1 ) Amortization: Prior service costs 1 1 1 — — Net (gain)/loss 5 1 1 — — Net periodic postretirement benefit cost $ 15 $ — $ 5 $ — $ 1 Six Months Ended June 30, 2017 Service cost $ 12 $ 3 $ 3 $ 1 $ 1 Interest cost 40 9 15 1 2 Expected return on plan assets (33 ) (14 ) (12 ) (1 ) (1 ) Amortization: Prior service costs 3 2 1 — — Net (gain)/loss 7 1 3 — — Net periodic postretirement benefit cost $ 29 $ 1 $ 10 $ 1 $ 2 Three Months Ended June 30, 2016 Service cost $ 6 $ 2 $ 1 $ 1 $ 1 Interest cost 17 4 7 — 1 Expected return on plan assets (14 ) (7 ) (5 ) (1 ) (1 ) Amortization: Prior service costs 1 1 1 — — Net (gain)/loss 4 1 2 — — Net periodic postretirement benefit cost $ 14 $ 1 $ 6 $ — $ 1 Six Months Ended June 30, 2016 Service cost $ 11 $ 3 $ 3 $ 1 $ 1 Interest cost 35 9 15 1 2 Expected return on plan assets (28 ) (13 ) (11 ) (1 ) (1 ) Amortization: Prior service costs 3 2 1 — — Net (gain)/loss 7 1 4 — — Net periodic postretirement benefit cost $ 28 $ 2 $ 12 $ 1 $ 2 Postretirement Benefits Southern Company Gas (in millions) Successor – Three Months Ended June 30, 2017 Service cost $ — Interest cost 2 Expected return on plan assets (1 ) Amortization: Prior service costs — Net (gain)/loss 1 Net periodic postretirement benefit cost $ 2 Successor – Six Months Ended June 30, 2017 Service cost $ 1 Interest cost 5 Expected return on plan assets (3 ) Amortization: Prior service costs (1 ) Net (gain)/loss 2 Net periodic postretirement benefit cost $ 4 Predecessor – Three Months Ended June 30, 2016 Service cost $ — Interest cost 2 Expected return on plan assets (1 ) Amortization: Prior service costs — Net (gain)/loss 1 Net periodic postretirement benefit cost $ 2 Predecessor – Six Months Ended June 30, 2016 Service cost $ 1 Interest cost 5 Expected return on plan assets (3 ) Amortization: Prior service costs (1 ) Net (gain)/loss 2 Net periodic postretirement benefit cost $ 4

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Summary of Valuation Allowance	At June 30, 2017 , valuation allowances were as follows: Mississippi Power Southern Company Gas Southern Company (in millions) Federal $ — $ 18 $ 18 State (net of federal benefit) 46 1 63 Balance at June 30, 2017 $ 46 $ 19 $ 81
Change in Unrecognized Tax Benefits	Changes during the six months ended June 30, 2017 for unrecognized tax benefits were as follows: Mississippi Power Southern Power Southern Company (in millions) Unrecognized tax benefits as of December 31, 2016 $ 465 $ 17 $ 484 Tax positions from current periods 3 1 10 Tax positions from prior periods — 1 7 Balance as of June 30, 2017 $ 468 $ 19 $ 501
Impact on Effective Tax Rate, If Recognized	The impact on the effective tax rate, if recognized, is as follows: As of June 30, 2017 As of December 31, 2016 Mississippi Power Southern Power Southern Company Southern Company (in millions) Tax positions impacting the effective tax rate $ 4 $ 19 $ 37 $ 20 Tax positions not impacting the effective tax rate 464 — 464 464 Balance of unrecognized tax benefits $ 468 $ 19 $ 501 $ 484

Derivatives (Tables)

Derivatives (Tables)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of energy-related derivatives	At June 30, 2017 , the net volume of energy-related derivative contracts for natural gas positions for the Southern Company system, 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 (*) 472 2021 2024 Alabama Power 70 2020 — Georgia Power 160 2020 — Gulf Power 35 2020 — Mississippi Power 41 2021 — Southern Power 25 2017 — Southern Company Gas (*) 141 2019 2024 (*) Southern Company's and 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 3.5 billion mmBtu and short natural gas positions of 3.4 billion mmBtu as of June 30, 2017 , which is also included in Southern Company's total volume.
Schedule of interest rate derivatives	At June 30, 2017 , the following interest rate derivatives were outstanding: Notional Amount Interest Rate Received Weighted Average Interest Rate Paid Hedge Maturity Date Fair Value (in millions) (in millions) Cash Flow Hedges of Existing Debt Mississippi Power $ 900 1-month 0.79% March 2018 $ 3 Fair Value Hedges of Existing Debt Southern Company (*) 250 1.30% 3-month August 2017 — Southern Company (*) 300 2.75% 3-month June 2020 1 Southern Company (*) 1,500 2.35% 1-month July 2021 (14 ) Georgia Power 250 5.40% 3-month June 2018 — Georgia Power 500 1.95% 3-month December 2018 (2 ) Georgia Power 200 4.25% 3-month December 2019 1 Southern Company Consolidated $ 3,900 $ (11 ) (*) Represents the Southern Company parent entity.
Schedule of foreign currency derivatives	At June 30, 2017 , the following foreign currency derivatives were outstanding: Pay Notional Pay Rate Receive Notional Receive Rate Hedge Fair Value (in millions) (in millions) (in millions) Cash Flow Hedges of Existing Debt Southern Power $ 677 2.95% € 600 1.00% June 2022 $ 18 Southern Power 564 3.78% 500 1.85% June 2026 15 Total $ 1,241 € 1,100 $ 33
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 June 30, 2017 As of December 31, 2016 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/Liabilities from risk management activities, net of collateral $ 23 $ 35 $ 73 $ 27 Other deferred charges and assets/Other deferred credits and liabilities 8 31 25 33 Total derivatives designated as hedging instruments for regulatory purposes $ 31 $ 66 $ 98 $ 60 Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Liabilities from risk management activities, net of collateral $ 13 $ 10 $ 23 $ 7 Interest rate derivatives: Other current assets/Liabilities from risk management activities, net of collateral 11 1 12 1 Other deferred charges and assets/Other deferred credits and liabilities — 22 1 28 Foreign currency derivatives: Other current assets/Liabilities from risk management activities, net of collateral — 23 — 25 Other deferred charges and assets/Other deferred credits and liabilities 56 — — 33 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 80 $ 56 $ 36 $ 94 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Liabilities from risk management activities, net of collateral $ 237 $ 202 $ 489 $ 483 Other deferred charges and assets/Other deferred credits and liabilities 102 86 66 81 Interest rate derivatives: Other current assets/Liabilities from risk management activities, net of collateral — — 1 — Total derivatives not designated as hedging instruments $ 339 $ 288 $ 556 $ 564 Gross amounts recognized $ 450 $ 410 $ 690 $ 718 Gross amounts offset (*) $ (219 ) $ (290 ) $ (462 ) $ (524 ) Net amounts recognized in the Balance Sheets $ 231 $ 120 $ 228 $ 194 As of June 30, 2017 As of December 31, 2016 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/Liabilities from risk management activities $ 7 $ 7 $ 13 $ 5 Other deferred charges and assets/Other deferred credits and liabilities 2 4 7 4 Total derivatives designated as hedging instruments for regulatory purposes $ 9 $ 11 $ 20 $ 9 Gross amounts recognized $ 9 $ 11 $ 20 $ 9 Gross amounts offset $ (6 ) $ (6 ) $ (8 ) $ (8 ) Net amounts recognized in the Balance Sheets $ 3 $ 5 $ 12 $ 1 Georgia Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 10 $ 4 $ 30 $ 1 Other deferred charges and assets/Other deferred credits and liabilities 5 10 14 7 Total derivatives designated as hedging instruments for regulatory purposes $ 15 $ 14 $ 44 $ 8 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ 1 $ 1 $ 2 $ — Other deferred charges and assets/Other deferred credits and liabilities — 2 — 3 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 1 $ 3 $ 2 $ 3 Gross amounts recognized $ 16 $ 17 $ 46 $ 11 Gross amounts offset $ (9 ) $ (9 ) $ (8 ) $ (8 ) Net amounts recognized in the Balance Sheets $ 7 $ 8 $ 38 $ 3 Gulf Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Liabilities from risk management activities $ 1 $ 16 $ 4 $ 12 Other deferred charges and assets/Other deferred credits and liabilities — 13 1 17 Total derivatives designated as hedging instruments for regulatory purposes $ 1 $ 29 $ 5 $ 29 Gross amounts recognized $ 1 $ 29 $ 5 $ 29 Gross amounts offset $ (1 ) $ (1 ) $ (4 ) $ (4 ) Net amounts recognized in the Balance Sheets $ — $ 28 $ 1 $ 25 As of June 30, 2017 As of December 31, 2016 Derivative Category and Balance Sheet Location Assets Liabilities Assets Liabilities (in millions) (in millions) Mississippi Power Derivatives designated as hedging instruments for regulatory purposes Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 6 $ 2 $ 6 Other deferred charges and assets/Other deferred credits and liabilities 1 4 2 5 Total derivatives designated as hedging instruments for regulatory purposes $ 2 $ 10 $ 4 $ 11 Derivatives designated as hedging instruments in cash flow and fair value hedges Interest rate derivatives: Other current assets/Other current liabilities $ 3 $ — $ 2 $ — Other deferred charges and assets/Other deferred credits and liabilities — — 1 — Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 3 $ — $ 3 $ — Gross amounts recognized $ 5 $ 10 $ 7 $ 11 Gross amounts offset $ (2 ) $ (2 ) $ (3 ) $ (3 ) Net amounts recognized in the Balance Sheets $ 3 $ 8 $ 4 $ 8 Southern Power Derivatives designated as hedging instruments in cash flow and fair value hedges Energy-related derivatives: Other current assets/Other current liabilities $ 13 $ 8 $ 18 $ 4 Foreign currency derivatives: Other current assets/Other current liabilities — 23 — 25 Other deferred charges and assets/Other deferred credits and liabilities 56 — — 33 Total derivatives designated as hedging instruments in cash flow and fair value hedges $ 69 $ 31 $ 18 $ 62 Derivatives not designated as hedging instruments Energy-related derivatives: Other current assets/Other current liabilities $ 1 $ 1 $ 3 $ 1 Interest rate derivatives: Other current assets/Other current liabilities — — 1 — Total derivatives not designated as hedging instruments $ 1 $ 1 $ 4 $ 1 Gross amounts recognized $ 70 $ 32 $ 22 $ 63 Gross amounts offset $ (2 ) $ (2 ) $ (5 ) $ (5 ) Net amounts recognized in the Balance Sheets $ 68 $ 30 $ 17 $ 58 As of June 30, 2017 As of December 31, 2016 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 $ 4 $ 2 $ 24 $ 3 Other deferred charges and assets/Other deferred credits and liabilities — — 1 — Total derivatives designated as hedging instruments for regulatory purposes $ 4 $ 2 $ 25 $ 3 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 $ — $ 2 $ 4 $ 3 Derivatives not designated as hedging instruments Energy-related derivatives: Assets from risk management activities/Liabilities from risk management activities-current $ 236 $ 201 $ 486 $ 482 Other deferred charges and assets/Other deferred credits and liabilities 102 86 66 81 Total derivatives not designated as hedging instruments $ 338 $ 287 $ 552 $ 563 Gross amounts of recognized $ 342 $ 291 $ 581 $ 569 Gross amounts offset (*) $ (196 ) $ (267 ) $ (435 ) $ (497 ) Net amounts recognized in the Balance Sheets $ 146 $ 24 $ 146 $ 72 (*) Gross amounts offset include cash collateral held on deposit in broker margin accounts of $71 million and $62 million as of June 30, 2017 and December 31, 2016 , respectively.
Pre-tax effects of unrealized derivative gains (losses) arising from energy-related derivative instruments	At June 30, 2017 and December 31, 2016 , 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 June 30, 2017 Derivative Category and Balance Sheet Location Southern Company (b) Alabama Power Georgia Power Gulf Power Mississippi Power Southern Company Gas (b) (in millions) Energy-related derivatives: Other regulatory assets, current $ (24 ) $ (3 ) $ — $ (15 ) $ (5 ) $ (1 ) Other regulatory assets, deferred (23 ) (2 ) (5 ) (13 ) (3 ) — Other regulatory liabilities, current (a) 13 3 6 — — 4 Total energy-related derivative gains (losses) $ (34 ) $ (2 ) $ 1 $ (28 ) $ (8 ) $ 3 (a) Georgia Power includes other regulatory liabilities, current in other current liabilities. (b) Fair value gains and losses recorded in regulatory assets and liabilities include cash collateral held on deposit in broker margin accounts of $ 1 million at June 30, 2017 . Regulatory Hedge Unrealized Gain (Loss) Recognized in the Balance Sheet at December 31, 2016 Derivative Category and Balance Sheet Location Southern Company (c) Alabama Power Georgia Power Gulf Power Mississippi Power Southern Company Gas (c) (in millions) Energy-related derivatives: Other regulatory assets, current $ (16 ) $ (1 ) $ — $ (9 ) $ (5 ) $ (1 ) Other regulatory assets, deferred (19 ) — — (16 ) (3 ) — Other regulatory liabilities, current (a) 56 8 29 1 1 17 Other regulatory liabilities, deferred (b) 12 4 7 — — 1 Total energy-related derivative gains (losses) $ 33 $ 11 $ 36 $ (24 ) $ (7 ) $ 17 (a) Georgia Power includes other regulatory liabilities, current in other current liabilities. (b) Georgia Power includes other regulatory liabilities, deferred in other deferred credits and liabilities. (c) 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 December 31, 2016 .
Pre-tax effects of interest rate derivatives, designated as cash flow hedging instruments	For the three months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives, interest rate derivatives, and foreign currency derivatives designated as cash flow hedging instruments were as follows: Derivatives in Cash Flow Hedging Relationships Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Statements of Income Location Amount 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy-related derivatives $ (9 ) $ — Depreciation and amortization $ (2 ) $ — Interest rate derivatives (1 ) 6 Interest expense, net of amounts capitalized (5 ) (4 ) Foreign currency derivatives 71 (39 ) Interest expense, net of amounts capitalized (5 ) (1 ) Other income (expense), net (*) 79 (20 ) Total $ 61 $ (33 ) $ 67 $ (25 ) Alabama Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (2 ) $ (2 ) Georgia Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (1 ) $ (1 ) Gulf Power Interest rate derivatives $ (1 ) $ (2 ) Interest expense, net of amounts capitalized $ — $ — Southern Power Energy-related derivatives $ (7 ) $ — Depreciation and amortization $ (2 ) $ — Foreign currency derivatives 71 (39 ) Interest expense, net of amounts capitalized (5 ) (1 ) Other income (expense), net (*) 79 (20 ) Total $ 64 $ (39 ) $ 72 $ (21 ) (*) 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 Southern Company Gas, the pre-tax effect of energy related derivatives and interest rate derivatives designated as cash flow hedging instruments recognized in OCI and those reclassified from accumulated OCI into earnings for the successor three months ended June 30, 2017 and the predecessor three months ended June 30, 2016 were as follows: Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Successor Predecessor Successor Predecessor Derivatives in Cash Flow Hedging Relationships Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Statements of Income Location Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Energy-related derivatives $ (2 ) $ — Cost of natural gas $ — $ (1 ) Interest rate derivatives — (19 ) Interest expense, net of amounts capitalized — (1 ) Total $ (2 ) $ (19 ) $ — $ (2 ) For the six months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives, interest rate derivatives, and foreign currency derivatives designated as cash flow hedging instruments were as follows: Derivatives in Cash Flow Gain (Loss) Gain (Loss) Reclassified from Accumulated OCI into Statements of Income Location Amount 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy-related derivatives $ (20 ) $ — Depreciation and amortization $ (6 ) $ — Interest rate derivatives (1 ) (184 ) Interest expense, net of amounts capitalized (10 ) (7 ) Foreign currency derivatives 67 (39 ) Interest expense, net of amounts capitalized (12 ) (1 ) Other income (expense), net (*) 96 (20 ) Total $ 46 $ (223 ) $ 68 $ (28 ) Alabama Power Interest rate derivatives $ — $ (4 ) Interest expense, net of amounts capitalized $ (3 ) $ (3 ) Georgia Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (3 ) $ (2 ) Gulf Power Energy-related derivatives $ (1 ) $ — Depreciation and amortization $ — $ — Interest rate derivatives (1 ) (7 ) Interest expense, net of amounts capitalized — — Total $ (2 ) $ (7 ) $ — $ — Mississippi Power Interest rate derivatives $ — $ — Interest expense, net of amounts capitalized $ (1 ) $ (1 ) Southern Power Energy-related derivatives $ (15 ) $ — Depreciation and amortization $ (6 ) $ — Interest rate derivatives — — Interest expense, net of amounts capitalized — (1 ) Foreign currency derivatives 67 (39 ) Interest expense, net of amounts capitalized (12 ) (1 ) Other income (expense), net (*) 96 (20 ) Total $ 52 $ (39 ) $ 78 $ (22 ) (*) 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 Southern Company Gas, the pre-tax effect of energy related derivatives and interest rate derivatives designated as cash flow hedging instruments recognized in OCI and those reclassified from accumulated OCI into earnings for the successor six months ended June 30, 2017 and the predecessor six months ended June 30, 2016 were as follows: Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Successor Predecessor Successor Predecessor Derivatives in Cash Flow Hedging Relationships Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Statements of Income Location Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Energy-related derivatives $ (4 ) $ — Cost of natural gas $ — $ (1 ) Interest rate derivatives — (64 ) Interest expense, net of amounts capitalized — — Total $ (4 ) $ (64 ) $ — $ (1 )
Pre tax effect of interest rate and energy related derivatives	For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of energy-related derivatives and interest rate derivatives not designated as hedging instruments on the statements of income were as follows: Gain (Loss) Three Months Ended Six Months Ended Derivatives in Non-Designated Hedging Relationships Statements of Income Location 2017 2016 2017 2016 (in millions) (in millions) Southern Company Energy Related derivatives: Natural gas revenues (*) $ 16 $ — $ 65 $ — Cost of natural gas (2 ) — (4 ) — Total derivatives in non-designated hedging relationships $ 14 $ — $ 61 $ — (*) Excludes gains (losses) recorded in cost of natural gas associated with weather derivatives of $1 million and $15 million for the three and six months ended June 30, 2017 , respectively. Gain (Loss) Successor Predecessor Successor Predecessor Derivatives in Non-Designated Hedging Relationships Statements of Income Location Three Months Ended Three Months Ended Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) Southern Company Gas Energy Related derivatives: Natural gas revenues (*) $ 16 $ (21 ) $ 65 $ (1 ) Cost of natural gas (2 ) (61 ) (4 ) (62 ) Total derivatives in non-designated hedging relationships $ 14 $ (82 ) $ 61 $ (63 ) (*) Excludes gains recorded in cost of natural gas associated with weather derivatives of $15 million for the successor six months ended June 30, 2017 and immaterial amounts for all other periods presented.
Pre-tax effects of interest rate derivatives, designated as fair value hedging instruments	For the three and six months ended June 30, 2017 and 2016 , the pre-tax effects of interest rate derivatives designated as fair value hedging instruments were as follows: Derivatives in Fair Value Hedging Relationships Gain (Loss) Three Months Ended June 30, Six Months Ended June 30, Derivative Category Statements of Income Location 2017 2016 2017 2016 (in millions) (in millions) Southern Company Interest rate derivatives: Interest expense, net of amounts capitalized $ 7 $ 4 $ (1 ) $ 24 Georgia Power Interest rate derivatives: Interest expense, net of amounts capitalized $ — $ — $ (1 ) $ 15

Acquisitions (Tables)

Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Schedule of Business Acquisitions	The following table presents the final purchase price allocation: PowerSecure Purchase Price (in millions) Current assets $ 172 Property, plant, and equipment 46 Intangible assets 106 Goodwill 284 Other assets 4 Current liabilities (121 ) Long-term debt, including current portion (48 ) Deferred credits and other liabilities (14 ) Total purchase price $ 429 The following table presents the final purchase price allocation: Southern Company Gas Purchase Price (in millions) Current assets $ 1,557 Property, plant, and equipment 10,108 Goodwill 5,967 Intangible assets 400 Regulatory assets 1,118 Other assets 229 Current liabilities (2,201 ) Other liabilities (4,742 ) Long-term debt (4,261 ) Noncontrolling interest (174 ) Total purchase price $ 8,001 During the six months ended June 30, 2017, in accordance with Southern Power's overall growth strategy, Southern Renewable Partnerships, LLC (SRP), one of Southern Power's wholly-owned subsidiaries, acquired the Bethel wind facility . Acquisition-related costs were expensed as incurred and were not material. Project Facility Resource Seller; Acquisition Date Approximate Nameplate Capacity ( MW ) Location Southern Power Percentage Ownership Actual COD PPA Contract Period Bethel Wind Invenergy, 276 Castro County, TX 100 % January 2017 12 years
Business Acquisition, Pro Forma Information	The following summarized unaudited pro forma consolidated statement of earnings information assumes that the acquisition of Southern Company Gas was completed on January 1, 2015. The summarized unaudited pro forma consolidated statement of earnings information includes adjustments for (i) intercompany sales, (ii) amortization of intangible assets, (iii) adjustments to interest expense to reflect current interest rates on Southern Company Gas debt and additional interest expense associated with borrowings by Southern Company to fund the Merger, and (iv) the elimination of nonrecurring expenses associated with the Merger. For the Six Months Ended June 30, 2016 Operating revenues (in millions) $ 10,346 Net income attributable to Southern Company (in millions) $ 1,255 Basic Earnings Per Share (EPS) $ 1.34 Diluted EPS $ 1.33
Schedule of Construction Projects	During the six months ended June 30, 2017 , in accordance with its overall growth strategy, Southern Power completed construction of and placed in service, or continued construction of, the projects set forth in the following table. Through June 30, 2017 , total costs of construction incurred for these projects were $421 million , of which $49 million remained in CWIP for the Mankato facility acquired in 2016. Total aggregate construction costs, excluding the acquisition costs, are expected to be $170 million to $190 million for the Mankato facility. The ultimate outcome of this matter cannot be determined at this time. Project Facility Resource Approximate Nameplate Capacity ( MW ) Location Actual/Expected COD PPA Contract Period Projects Completed During the Six Months Ended June 30, 2017 East Pecos Solar 120 Pecos County, TX March 2017 15 years Lamesa Solar 102 Dawson County, TX April 2017 15 years Project Under Construction as of June 30, 2017 Mankato Natural Gas 345 Mankato, MN Second quarter 2019 20 years

Joint Ownership Agreements (Tab

Joint Ownership Agreements (Tables)	6 Months Ended
	Jun. 30, 2017
Regulated Operations [Abstract]
Equity Method Investments	Selected financial information of SNG for the three and six months ended June 30, 2017 is as follows: Income Statement Information Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 (in millions) Revenues $ 143 $ 298 Operating income $ 63 $ 147 Net income $ 48 $ 114 The carrying amounts of Southern Company Gas' equity method investments as of June 30, 2017 and December 31, 2016 and related income from those investments for the successor three and six month periods ended June 30, 2017 and the predecessor three and six month periods ended June 30, 2016 were as follows: Balance Sheet Information June 30, 2017 December 31, 2016 (in millions) SNG $ 1,405 $ 1,394 Atlantic Coast Pipeline 53 33 PennEast Pipeline 45 22 Triton 43 44 Pivotal JAX LNG, LLC 32 16 Horizon Pipeline 31 30 Other 1 2 Total $ 1,610 $ 1,541
Schedule of Other Nonoperating Income, by Component	Successor Predecessor Successor Predecessor Income Statement Information Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 (in millions) (in millions) (in millions) (in millions) SNG $ 24 $ — $ 58 $ — Triton 2 1 2 1 PennEast Pipeline 1 — 4 — Atlantic Coast Pipeline 2 — 3 — Horizon Pipeline — — 1 1 Total $ 29 $ 1 $ 68 $ 2

Segment and Related Informati32

Segment and Related Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Financial data for business segments	Financial data for business segments and products and services for the three and six months ended June 30, 2017 and 2016 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 Operating revenues $ 4,157 $ 529 $ (101 ) $ 4,585 $ 716 $ 166 $ (37 ) $ 5,430 Segment net income (loss) (a)(b) (1,442 ) 82 — (1,360 ) 49 (68 ) (2 ) (1,381 ) Six Months Ended Operating revenues $ 7,943 $ 979 $ (206 ) $ 8,716 $ 2,276 $ 289 $ (79 ) $ 11,202 Segment net income (loss) (a)(b)(c) (1,010 ) 151 — (859 ) 288 (152 ) — (723 ) Total assets at June 30, 2017 $ 71,503 $ 14,703 $ (317 ) $ 85,889 $ 21,809 $ 2,348 $ (1,362 ) $ 108,684 Three Months Ended Operating revenues $ 4,115 $ 373 $ (109 ) $ 4,379 $ — $ 125 $ (45 ) $ 4,459 Segment net income (loss) (a)(b) 599 89 — 688 — (61 ) (4 ) 623 Six Months Ended Operating revenues $ 7,884 $ 688 $ (212 ) $ 8,360 $ — $ 172 $ (81 ) $ 8,451 Segment net income (loss) (a)(b) 1,064 139 — 1,203 — (84 ) (7 ) 1,112 Total assets at December 31, 2016 $ 72,141 $ 15,169 $ (316 ) $ 86,994 $ 21,853 $ 2,474 $ (1,624 ) $ 109,697 (a) Attributable to Southern Company. (b) Segment net income (loss) for the traditional electric operating companies includes pre-tax charges for estimated probable losses on the Kemper IGCC of $3.0 billion ( $2.1 billion after tax) and $81 million ( $50 million after tax) for the three months ended June 30, 2017 and 2016 , respectively, and $3.1 billion ( $2.2 billion after tax) and $134 million ( $83 million after tax) for the six months ended June 30, 2017 and 2016 , respectively. See Note (B) under " Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate " for additional information. (c) Segment net income (loss) for the traditional electric operating companies also includes a pre-tax charge for the write-down of Gulf Power's ownership of Plant Scherer Unit 3 of $33 million ( $20 million after tax) for the six months ended June 30, 2017 . See Note (B) under " Regulatory Matters – Gulf Power – Retail Base Rate Cases " for additional information. Business segment financial data for the successor three and six months ended June 30, 2017 and the predecessor three and six months ended June 30, 2016 was as follows: Gas Distribution Operations Gas Marketing Services Wholesale Gas Services (*) Gas Midstream Operations Total All Other Eliminations Consolidated (in millions) Successor – Three Months Ended June 30, 2017: Operating revenues $ 603 $ 166 $ (12 ) $ 12 $ 769 $ 3 $ (56 ) $ 716 Segment net income 54 4 (17 ) 9 50 (1 ) — 49 Successor – Six Months Ended June 30, 2017: Operating revenues $ 1,783 $ 454 $ 119 $ 37 $ 2,393 $ 5 $ (122 ) $ 2,276 Segment net income 171 35 51 25 282 6 — 288 Successor – Total assets at $ 18,257 $ 2,093 $ 989 $ 2,381 $ 23,720 $ 11,182 $ (13,093 ) $ 21,809 Gas Distribution Operations Gas Marketing Services Wholesale Gas Services (*) Gas Midstream Operations Total All Other Eliminations Consolidated (in millions) Predecessor – Three Months Ended June 30, 2016: Operating revenues $ 547 $ 149 $ (95 ) $ 10 $ 611 $ 2 $ (42 ) $ 571 Segment EBIT 118 29 (112 ) (5 ) 30 (55 ) 1 (24 ) Predecessor – Six Months Ended June 30, 2016: Operating revenues $ 1,575 $ 435 $ (32 ) $ 25 $ 2,003 $ 4 $ (102 ) $ 1,905 Segment EBIT 353 109 (68 ) (6 ) 388 (60 ) — 328 Successor – Total assets at $ 19,453 $ 2,084 $ 1,127 $ 2,211 $ 24,875 $ 11,145 $ (14,167 ) $ 21,853 (*) 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) Successor – Three Months Ended June 30, 2017 $ 1,531 $ 123 $ 1,654 $ 1,666 $ (12 ) Successor – Six Months Ended June 30, 2017 3,370 259 3,629 3,510 119 Predecessor – Three Months Ended June 30 , 2016 $ 1,061 $ 58 $ 1,119 $ 1,214 $ (95 ) Predecessor – Six Months Ended June 30 , 2016 2,500 143 2,643 2,675 (32 )
Financial data for products and services	Products and Services Electric Utilities' Revenues Period Retail Wholesale Other Total (in millions) Three Months Ended June 30, 2017 $ 3,777 $ 618 $ 190 $ 4,585 Three Months Ended June 30, 2016 3,748 446 185 4,379 Six Months Ended June 30, 2017 $ 7,171 $ 1,149 $ 396 $ 8,716 Six Months Ended June 30, 2016 7,124 842 394 8,360 Southern Company Gas' Revenues Period Gas Gas Other Total (in millions) Three Months Ended June 30, 2017 $ 557 $ 166 $ (7 ) $ 716 Six Months Ended June 30, 2017 $ 1,689 $ 454 $ 133 $ 2,276

Introduction - Narrative (Detai

Introduction - Narrative (Details)	Apr. 04, 2017USD ($)	Apr. 01, 2017	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)kWh	Jun. 30, 2016USD ($)
GEORGIA POWER CO
Related Party Transaction [Line Items]
Property damage reserve, percentage of balance		0.75
GULF POWER CO
Related Party Transaction [Line Items]
PSC approved annual property damage reserve accrual	$ 3,500,000
Number of agreements for renewable generation	0		$ 40,000,000		$ 40,000,000
Increase (decrease) in recoverable property damage costs	$ 31,000,000
Recovery period for natural disaster reserve costs					60 days
Cumulative costs limit under PSC order					$ 100,000,000
SOUTHERN Co GAS | GEORGIA POWER CO
Related Party Transaction [Line Items]
Related party transactions					9,000,000
SOUTHERN Co GAS | SOUTHERN POWER CO
Related Party Transaction [Line Items]
Related party transactions					56,000,000
Southern Natural Gas Company, LLC | SOUTHERN Co GAS
Related Party Transaction [Line Items]
Related party transactions					16,000,000
Southern Natural Gas Company, LLC | ALABAMA POWER CO
Related Party Transaction [Line Items]
Related party transactions					4,000,000
Southern Natural Gas Company, LLC | GEORGIA POWER CO
Related Party Transaction [Line Items]
Related party transactions					51,000,000
Southern Natural Gas Company, LLC | SOUTHERN POWER CO
Related Party Transaction [Line Items]
Related party transactions					13,000,000
Maximum | GULF POWER CO
Related Party Transaction [Line Items]
Customer surcharge storm recovery costs					$ 4
Customer surcharge storm recovery capacity | kWh					1,000
Wholesale Gas Services | SOUTHERN Co GAS
Related Party Transaction [Line Items]
Inventory write-down					$ 0
Predecessor | Wholesale Gas Services | SOUTHERN Co GAS
Related Party Transaction [Line Items]
Inventory write-down			$ 0	$ 0		$ 0

Introduction - Goodwill (Detail

Introduction - Goodwill (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 6,271	$ 6,251
SOUTHERN POWER CO
Goodwill [Line Items]
Goodwill	2	2
SOUTHERN Co GAS
Goodwill [Line Items]
Goodwill	5,967	5,967
SOUTHERN Co GAS | Gas distribution operations
Goodwill [Line Items]
Goodwill	4,702	4,702
SOUTHERN Co GAS | Gas marketing services
Goodwill [Line Items]
Goodwill	$ 1,265	$ 1,265

Introduction - Other Intangible

Introduction - Other Intangibles (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 980,000,000	$ 957,000,000
Accumulated Amortization	(126,000,000)	(62,000,000)
Other Intangible Assets, Net	854,000,000	895,000,000
Total other intangible assets - gross	1,055,000,000	1,032,000,000
Total other intangible assets - net	929,000,000	970,000,000
Customer relationships | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	288,000,000	268,000,000
Accumulated Amortization	(57,000,000)	(32,000,000)
Other Intangible Assets, Net	231,000,000	236,000,000
Trade names | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	159,000,000	158,000,000
Accumulated Amortization	(11,000,000)	(5,000,000)
Other Intangible Assets, Net	148,000,000	153,000,000
Patents | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	4,000,000	4,000,000
Accumulated Amortization	0	0
Other Intangible Assets, Net	4,000,000	4,000,000
Backlog | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	5,000,000	5,000,000
Accumulated Amortization	(1,000,000)	(1,000,000)
Other Intangible Assets, Net	4,000,000	4,000,000
Storage and transportation contracts | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	64,000,000	64,000,000
Accumulated Amortization	(21,000,000)	(2,000,000)
Other Intangible Assets, Net	43,000,000	62,000,000
Software and other | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	4,000,000	2,000,000
Accumulated Amortization	(1,000,000)	0
Other Intangible Assets, Net	3,000,000	2,000,000
PPA fair value adjustments | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	456,000,000	456,000,000
Accumulated Amortization	(35,000,000)	(22,000,000)
Other Intangible Assets, Net	421,000,000	434,000,000
Federal Communications Commission licenses | Southern Company
Indefinite-lived Intangible Assets [Line Items]
Other intangible assets not subject to amortization	75,000,000	75,000,000
SOUTHERN POWER CO
Indefinite-lived Intangible Assets [Line Items]
Accumulated Amortization	(35,000,000)	(22,000,000)
SOUTHERN POWER CO | PPA fair value adjustments
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	456,000,000	456,000,000
Accumulated Amortization	(35,000,000)	(22,000,000)
Other Intangible Assets, Net	421,000,000	434,000,000
SOUTHERN Co GAS
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	400,000,000	400,000,000
Accumulated Amortization	(80,000,000)	(34,000,000)
Other Intangible Assets, Net	320,000,000	366,000,000
Total other intangible assets - net	320,000,000	366,000,000
SOUTHERN Co GAS | Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	221,000,000	221,000,000
Accumulated Amortization	(53,000,000)	(30,000,000)
Other Intangible Assets, Net	168,000,000	191,000,000
SOUTHERN Co GAS | Trade names
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	115,000,000	115,000,000
Accumulated Amortization	(6,000,000)	(2,000,000)
Other Intangible Assets, Net	109,000,000	113,000,000
SOUTHERN Co GAS | Storage and transportation contracts
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	64,000,000	64,000,000
Accumulated Amortization	(21,000,000)	(2,000,000)
Other Intangible Assets, Net	$ 43,000,000	$ 62,000,000

Introduction - Intangibles, Amo

Introduction - Intangibles, Amortization (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 29	$ 65
SOUTHERN POWER CO
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	6	13
SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 20	$ 46

Contingencies and Regulatory 37

Contingencies and Regulatory Matters - Narrative (Details)	Jul. 01, 2017USD ($)	Jun. 30, 2017USD ($)MW	Jun. 09, 2017USD ($)	May 04, 2017USD ($)	Apr. 04, 2017intervenor	Mar. 31, 2017USD ($)	Mar. 27, 2017	Mar. 10, 2017USD ($)	Feb. 21, 2017USD ($)	Dec. 20, 2016USD ($)	May 01, 2016USD ($)	Mar. 31, 2016	Jan. 01, 2016	Apr. 28, 2017USD ($)	Sep. 30, 2016USD ($)	Jan. 31, 2016USD ($)	Jun. 30, 2017USD ($)MW	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)clauseMW	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2018	Aug. 31, 2018	Dec. 31, 2017USD ($)	Mar. 31, 2017	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2008USD ($)	Jun. 30, 2017USD ($)MW	Dec. 31, 2020USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)MW	Jan. 01, 2121	Aug. 01, 2017	Jul. 06, 2017USD ($)	Jun. 23, 2017USD ($)	May 31, 2017USD ($)	May 01, 2017	Mar. 07, 2017USD ($)	Feb. 17, 2017USD ($)	Aug. 31, 2016USD ($)
Loss Contingencies [Line Items]
Lawsuit deferral period							30 days
Maximum borrowing capacity		$ 8,168,000,000															$ 8,168,000,000		$ 8,168,000,000													$ 8,168,000,000			$ 8,168,000,000
Stockholders' equity, including portion attributable to noncontrolling interest		(25,241,000,000)															(25,241,000,000)	$ (23,446,000,000)	(25,241,000,000)	$ (26,612,000,000)	$ (23,446,000,000)					$ (26,612,000,000)	$ (21,982,000,000)					(25,241,000,000)		$ (23,446,000,000)	(25,241,000,000)
Property, plant and equipment, gross		101,021,000,000															101,021,000,000		101,021,000,000	98,416,000,000						98,416,000,000						101,021,000,000			101,021,000,000
SOUTHERN POWER CO
Loss Contingencies [Line Items]
Maximum borrowing capacity		750,000,000															750,000,000		750,000,000													750,000,000			750,000,000					$ 600,000,000
Stockholders' equity, including portion attributable to noncontrolling interest		(5,814,000,000)															(5,814,000,000)		(5,814,000,000)	(5,675,000,000)						(5,675,000,000)						(5,814,000,000)			(5,814,000,000)
Wholesale revenues, non-affiliates																	436,000,000	264,000,000	783,000,000		480,000,000
Property, plant and equipment, gross		13,731,000,000															13,731,000,000		13,731,000,000	12,728,000,000						12,728,000,000						13,731,000,000			13,731,000,000
GEORGIA POWER CO
Loss Contingencies [Line Items]
Environmental remediation liability		12,000,000															12,000,000		$ 12,000,000	17,000,000						17,000,000						12,000,000			12,000,000
Cost recovery, new nuclear																																										$ 50,000,000
Percentage of Proportionate share owed in consortium agreement																															45.70%
Liquidated damages, percentage																			40.00%												10.00%
Maximum borrowing capacity		1,750,000,000															1,750,000,000		$ 1,750,000,000													1,750,000,000			1,750,000,000
Weekly payment of services under contract agreement														$ 5,400,000
Estimated in-service capital cost																														$ 4,418,000,000
Financing costs collected, net of tax																			1,400,000,000
Additional construction capital costs										$ 3,300,000,000										222,000,000														$ 3,700,000,000
Estimate of possible loss										$ 240,000,000
Retail rate of return on common equity																													10.95%
Public utilities, approved return on equity percentage													10.00%
Financing costs incurred																																			1,400,000,000
Estimated cancellation costs																																			400,000,000
Wholesale revenues, non-affiliates																	40,000,000	40,000,000	79,000,000		82,000,000
Property, plant and equipment, gross		34,410,000,000															34,410,000,000		34,410,000,000	33,841,000,000						33,841,000,000						34,410,000,000			34,410,000,000
GEORGIA POWER CO | Minimum
Loss Contingencies [Line Items]
Estimated financing costs																																			3,100,000,000
GEORGIA POWER CO | Maximum
Loss Contingencies [Line Items]
Estimated financing costs																																			3,500,000,000
GEORGIA POWER CO | Other current liabilities
Loss Contingencies [Line Items]
Over recovered fuel balance		61,000,000															61,000,000		61,000,000													61,000,000			61,000,000
GEORGIA POWER CO | Other deferred credits and liabilities
Loss Contingencies [Line Items]
Over recovered fuel balance																				84,000,000						84,000,000
GULF POWER CO
Loss Contingencies [Line Items]
Environmental remediation liability		51,000,000															51,000,000		51,000,000	44,000,000						44,000,000						51,000,000			51,000,000
Maximum borrowing capacity		$ 280,000,000															$ 280,000,000		$ 280,000,000													$ 280,000,000			$ 280,000,000
Retail rate of return on common equity		10.25%															10.25%		10.25%													10.25%			10.25%
Reduction in depreciation expense																			$ 34,000,000							0	$ 20,100,000	$ 8,400,000	$ 62,500,000
Wholesale revenues, non-affiliates																	$ 12,000,000	15,000,000	30,000,000		31,000,000
Loss on Plant Scherer Unit 3																	0	0	$ 33,000,000		0
Number of regulatory clauses | clause																			4
Property, plant and equipment, gross		$ 5,156,000,000															$ 5,156,000,000		$ 5,156,000,000	5,140,000,000						5,140,000,000						$ 5,156,000,000			$ 5,156,000,000
GULF POWER CO | Minimum
Loss Contingencies [Line Items]
Retail rate of return on common equity		9.25%															9.25%		9.25%													9.25%			9.25%
GULF POWER CO | Maximum
Loss Contingencies [Line Items]
Retail rate of return on common equity		11.25%															11.25%		11.25%													11.25%			11.25%
SOUTHERN Co GAS
Loss Contingencies [Line Items]
Environmental remediation liability		$ 416,000,000															$ 416,000,000		$ 416,000,000	426,000,000						426,000,000						$ 416,000,000			$ 416,000,000
Maximum borrowing capacity		1,900,000,000															1,900,000,000		1,900,000,000													1,900,000,000			1,900,000,000
Stockholders' equity, including portion attributable to noncontrolling interest		(9,242,000,000)															(9,242,000,000)		(9,242,000,000)	(9,109,000,000)						(9,109,000,000)						(9,242,000,000)			(9,242,000,000)
Property, plant and equipment, gross		14,850,000,000															14,850,000,000		14,850,000,000	14,508,000,000						14,508,000,000						14,850,000,000			14,850,000,000
MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Gain contingency, surcharge revenue																										5,000,000
Increase in base rate under cost based electric tariff due to settlement											$ 7,000,000
AFUDC cost																			22,000,000
Fuel cost recovery		14,000,000															14,000,000		14,000,000	37,000,000						37,000,000						14,000,000			14,000,000
Maximum borrowing capacity		113,000,000															113,000,000		113,000,000													113,000,000			113,000,000
Wholesale revenues, non-affiliates																	62,000,000	60,000,000	124,000,000		120,000,000
Maximum annual percentage increase in revenue				2.00%																																					2.00%
Maximum annual increase in revenue				$ 18,000,000
Deferred revenue				$ 26,000,000
Property, plant and equipment, gross		4,826,000,000															4,826,000,000		4,826,000,000	4,865,000,000						4,865,000,000						4,826,000,000			4,826,000,000
ALABAMA POWER CO
Loss Contingencies [Line Items]
Maximum borrowing capacity		1,335,000,000															1,335,000,000		1,335,000,000													1,335,000,000			1,335,000,000
Wholesale revenues, non-affiliates																	68,000,000	$ 67,000,000	133,000,000		$ 130,000,000
Property, plant and equipment, gross		26,466,000,000															26,466,000,000		26,466,000,000	26,031,000,000						26,031,000,000						26,466,000,000			26,466,000,000
ALABAMA POWER CO | Regulatory assets, deferred
Loss Contingencies [Line Items]
Over (under) recovered environmental clause																																											$ 36,000,000
Atlanta Gas Light
Loss Contingencies [Line Items]
Public utilities, approved return on equity percentage									10.75%
Approved increase (decrease) in fuel rates amount									$ 20,000,000
Elizabethtown Gas
Loss Contingencies [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 13,000,000													$ 19,000,000
Test year duration																									12 months
Public utilities, requested return on equity, percentage		9.60%													10.25%
Public utilities, property, plant and equipment, accumulated depreciation		$ 3,000,000															3,000,000		3,000,000													3,000,000			3,000,000
Nicor Gas
Loss Contingencies [Line Items]
Maximum borrowing capacity		700,000,000															700,000,000		700,000,000													700,000,000			700,000,000					700,000,000
Public utilities, requested rate increase (decrease), amount								$ 208,000,000
Public utilities, requested return on equity, percentage								10.70%
Statutory time limit								11 months
Virginia Natural Gas
Loss Contingencies [Line Items]
Public utilities, requested return on equity, percentage						10.25%
Florida City Gas
Loss Contingencies [Line Items]
Infrastructure replacement program, petitioned investment amount		7,000,000															7,000,000		7,000,000													7,000,000			7,000,000
RE Roserock, LLC | SOUTHERN POWER CO
Loss Contingencies [Line Items]
Ownership percentage by parent																											51.00%
Loss Contingency, Payments																			26,000,000
Location One | SOUTHERN Co GAS
Loss Contingencies [Line Items]
Environmental remediation liability		5,000,000															5,000,000		5,000,000													5,000,000			5,000,000
Kemper Igcc [Member] | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Estimated Cost Incurred After in Service Date																																								$ 175,000,000
Period of amortization of regulatory assets												36 months
AFUDC cost																																493,000,000
Plant Vogtle Units 3 And 4
Loss Contingencies [Line Items]
Guarantor obligations			$ 3,680,000,000
Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Liquidated damages, monetary amount																			1,700,000,000												$ 920,000,000
Liquidated damages, monetary amount Received, based on percentage of ownership																															$ 420,000,000
Maximum borrowing capacity																$ 920,000,000
Guarantor obligations			$ 1,700,000,000
Requested rate increase (decrease) amount																			400,000,000
Plant Scherer Unit 3
Loss Contingencies [Line Items]
Loss on Plant Scherer Unit 3																			$ 33,000,000
Plant Scherer Unit 3 | GULF POWER CO
Loss Contingencies [Line Items]
Number of intervenors | intervenor					3
Plant Smith Units 1 and 2 | GULF POWER CO
Loss Contingencies [Line Items]
Capacity of units included in request for decertification of units | MW																			357
Plant Scherer Unit Three | GULF POWER CO
Loss Contingencies [Line Items]
Loss on Plant Scherer Unit 3																			$ 32,500,000
MRA Revenue | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Fuel cost recovery		7,000,000															7,000,000		7,000,000	$ 13,000,000						$ 13,000,000						7,000,000			7,000,000
Westinghouse | Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed																60 days
Vogtle Owners | Interim Assessment Agreement
Loss Contingencies [Line Items]
Loss Contingency, Payments																			552,000,000
Estimate of possible loss		650,000,000															650,000,000		650,000,000													650,000,000			650,000,000
Vogtle Owners | Removal of Subcontractor Liens
Loss Contingencies [Line Items]
Loss Contingency, Payments																			354,000,000
Estimate of possible loss		400,000,000															400,000,000		400,000,000													400,000,000			400,000,000
Vogtle Owners | GEORGIA POWER CO | Interim Assessment Agreement
Loss Contingencies [Line Items]
Estimate of possible loss		297,000,000															297,000,000		297,000,000													297,000,000			297,000,000
Vogtle Owners | GEORGIA POWER CO | Removal of Subcontractor Liens
Loss Contingencies [Line Items]
Estimate of possible loss		183,000,000															183,000,000		183,000,000													183,000,000			183,000,000
Vogtle Owners | Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed			30 days
Restatement Adjustment | Toshiba
Loss Contingencies [Line Items]
Stockholders' equity, including portion attributable to noncontrolling interest																																							$ 5,000,000,000
Scenario, Forecast | GEORGIA POWER CO
Loss Contingencies [Line Items]
Additional construction capital costs																																	$ 5,440,000,000
Percent of basis points																																	0.95%			0.30%
Increase (decrease) in basis points																																	$ (8,000,000)
Amendment to estimated in-service capital cost																																	$ 5,680,000,000
Scenario, Forecast | GULF POWER CO
Loss Contingencies [Line Items]
Overall net customer impact from rate case settlement agreement																								$ 54,300,000
Increase (decrease) in revenue to be received from base rate change	$ 62,000,000
Wholesale revenues, non-affiliates																								$ 7,700,000
Retail regulatory equity ratio	0.525
Scenario, Forecast | Virginia Natural Gas
Loss Contingencies [Line Items]
Test year duration																							12 months
FFB Loan | GEORGIA POWER CO
Loss Contingencies [Line Items]
Maximum borrowing capacity		$ 2,600,000,000															$ 2,600,000,000		$ 2,600,000,000													$ 2,600,000,000			$ 2,600,000,000
Retirement Of Plant | Scenario, Forecast | GULF POWER CO
Loss Contingencies [Line Items]
Regulatory asset, amortization period																						15 years
Plant Scherer Unit Three | GULF POWER CO
Loss Contingencies [Line Items]
Electric generating units, capacity | MW		205															205		205													205			205
SAVE Program | Virginia Natural Gas
Loss Contingencies [Line Items]
Infrastructure replacement program, petitioned investment amount		$ 44,000,000															$ 44,000,000		$ 44,000,000													$ 44,000,000			$ 44,000,000
Regulated operation, allowable cost recovery						$ 13,000,000
Approved infrastructure replacement program		14,000,000															14,000,000		14,000,000													14,000,000			14,000,000
Regulatory Infrastructure Program | Nicor Gas
Loss Contingencies [Line Items]
Program duration period																												9 years
Property, plant and equipment, gross		75,000,000															75,000,000		75,000,000													75,000,000			75,000,000
STRIDE | Atlanta Gas Light
Loss Contingencies [Line Items]
Approved infrastructure replacement program		94,000,000															94,000,000		$ 94,000,000													94,000,000			94,000,000
Integrated System Reinforcement Program | Atlanta Gas Light
Loss Contingencies [Line Items]
Infrastructure replacement program, petitioned investment amount																																												$ 177,000,000
Integrated System Reinforcement Program | Atlanta Gas Light | Minimum
Loss Contingencies [Line Items]
Program duration period																			4 years
Aging Infrastructure Replacement Program | Elizabethtown Gas
Loss Contingencies [Line Items]
Approved infrastructure replacement program		$ 12,000,000															$ 12,000,000		$ 12,000,000													$ 12,000,000			$ 12,000,000
Subsequent Event | SOUTHERN POWER CO
Loss Contingencies [Line Items]
Ownership percentage by parent																																					100.00%
Subsequent Event | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Percentage of PSC retail rate increase																																						0.85%
PSC retail rate increase (decrease)																																						$ 8,000,000
Subsequent Event | Energy Efficiency Cost Rider | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
PSC retail rate increase (decrease)																																						$ 2,000,000

Contingencies and Regulatory 38

Contingencies and Regulatory Matters - Recovery Balance of Each Regulatory Clause - Alabama Power (Details) - ALABAMA POWER CO - USD ($) $ in Millions	Jun. 30, 2017	Feb. 17, 2017	Dec. 31, 2016
Deferred under recovered regulatory clause revenues
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 6		$ 9
Rate CNP PPA	0		142
Over recovered regulatory clause revenues
Loss Contingencies [Line Items]
Rate CNP PPA	1		0
Other regulatory liabilities, current
Loss Contingencies [Line Items]
Retail Energy Cost Recovery	11		76
Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Natural Disaster Reserve	$ 56		$ 69
Regulatory assets, deferred
Loss Contingencies [Line Items]
Over (under) recovered environmental clause		$ 36

Contingencies and Regulatory 39

Contingencies and Regulatory Matters - Revised Cost and Schedule - Georgia Power (Details) - USD ($) $ in Millions	6 Months Ended	102 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Construction work in progress	$ 7,440	$ 7,440	$ 8,977
GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	5,422	5,422	$ 4,939
Financing costs incurred		1,400
Financing costs collected, net of tax	1,400
Estimated cancellation costs		400
GEORGIA POWER CO | Minimum
Loss Contingencies [Line Items]
Preliminary estimated cost to complete	3,900	3,900
Construction work in progress	4,480	4,480
Guarantee Obligations	(1,680)	(1,680)
Estimated capital costs	6,700	6,700
Vogtle Cost Settlement Agreement Revised Forecast	(5,680)	(5,680)
Estimated net additional capital costs	1,020	1,020
Estimated financing costs		3,100
GEORGIA POWER CO | Maximum
Loss Contingencies [Line Items]
Preliminary estimated cost to complete	4,600	4,600
Construction work in progress	4,480	4,480
Guarantee Obligations	(1,680)	(1,680)
Estimated capital costs	7,400	7,400
Vogtle Cost Settlement Agreement Revised Forecast	(5,680)	(5,680)
Estimated net additional capital costs	1,720	1,720
Estimated financing costs		3,500
Cancellation Decision | GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	4,500	4,500
Financing costs collected, net of tax		1,400
Estimated cancellation costs		400
Total	$ 6,300	$ 6,300

Contingencies and Regulatory 40

Contingencies and Regulatory Matters - Recovery Balance of Each Regulatory Clause - Gulf Power (Details) - GULF POWER CO - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other regulatory liabilities, current
Loss Contingencies [Line Items]
Fuel Cost Recovery	$ 0	$ 15
Over recovered regulatory clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	7	0
Purchased Power Capacity Recovery	5	0
Environmental Cost Recovery	12	13
Energy Conservation Cost Recovery	$ 2	$ 4

Contingencies and Regulatory 41

Contingencies and Regulatory Matters - IGCC (Details) $ in Millions	Jun. 28, 2017USD ($)	Jun. 21, 2017	Nov. 17, 2016USD ($)	Jun. 09, 2016USD ($)	Jun. 03, 2016	Apr. 08, 2016USD ($)	Dec. 03, 2015USD ($)	Aug. 13, 2015USD ($)	Jul. 07, 2015USD ($)	Jun. 03, 2015USD ($)	Jan. 01, 2014USD ($)	Mar. 19, 2013	Jun. 30, 2017USD ($)mi	Mar. 31, 2016USD ($)	Jan. 31, 2013USD ($)	May 31, 2017USD ($)	Jun. 30, 2017USD ($)mi	Jun. 30, 2016USD ($)	May 31, 2017USD ($)	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)miMW	Jun. 30, 2016USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2010	Jun. 30, 2017USD ($)mi	May 31, 2017USD ($)	Dec. 31, 2016USD ($)	May 20, 2015USD ($)
Loss Contingencies [Line Items]
Unrecognized tax benefits													$ 501				$ 501				$ 501				$ 501		$ 484
MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Plant capacity under coal gasification combined cycle technology | MW																					582
Cost related to grant funding																							$ 245
Maximum cap construction cost																							2,880
Reduced percentage interest transferred under asset purchase agreement												15.00%												15.00%
Public utilities, approved rate increase (decrease), percentage											3.00%
Settlement agreement collection amount to mitigate rate impact, year two											$ 156
Retail rate recovery									$ 342
Carrying costs associated with retail rate recovery									$ 29
AFUDC cost																					$ 22
Interest bearing refundable deposit related to assets sale																												$ 275
Promissory note										$ 301
Unrecognized tax benefits													468				468				468				468		$ 465
Kemper Igcc [Member]
Loss Contingencies [Line Items]
Pre-tax charge to income																	3,000	$ 81			3,100	$ 134
After tax charge to income																	2,100	$ 50			2,200	$ 83
Unrecognized tax benefits													$ 464				$ 464				$ 464				$ 464
Kemper Igcc [Member] | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Purchase of Interest													100.00%				100.00%				100.00%				100.00%
Pipeline infrastructure | mi													61				61				61				61
Estimated cost			$ 68																		$ 5,680		2,880		$ 2,880
Cost related to grant funding																					(140)
Maximum cap construction cost																					$ 7,090
Period of commercial operations established by discovery docket																					5 years
Government grants received						$ 137
Pre-tax charge to income													$ 2,800			$ 196	$ 3,000		$ 305		$ 3,100					$ 3,070
After tax charge to income													2,000			$ 121			$ 188							$ 1,890
Construction and development costs																					1,300
Settlement agreement, term to file		45 days
Period from settlement agreement to hearing		45 days
CIP expenditures incurred but not yet paid																					3,300
Average annual increase (decrease) in operations and maintenance expenses																					105
Average annual increase (decrease) in maintenance capital																					44
Regulatory assets													117				117				117				117
Regulatory liabilities													10				10				10				10
AFUDC cost																									493
Proceeds from bonus depreciation																					370
Proceeds from income tax refunds																					82
Unrecognized tax benefits													464				464				$ 464				464
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Minimum
Loss Contingencies [Line Items]
Amortization period of regulatory assets and liabilities																					2 years
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Maximum
Loss Contingencies [Line Items]
Amortization period of regulatory assets and liabilities																					10 years
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, value of damages sought	$ 500			$ 100
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Property, Plant and Equipment
Loss Contingencies [Line Items]
Construction and development costs																					$ 1,200
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Materials And Supplies
Loss Contingencies [Line Items]
Construction and development costs																					14
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Other regulatory assets current
Loss Contingencies [Line Items]
Construction and development costs																					22
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Construction and development costs																					95
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Transmission and Related Regulatory Assets
Loss Contingencies [Line Items]
Construction and development costs																					800
Kemper Igcc [Member] | MISSISSIPPI POWER CO | Assets, Current
Loss Contingencies [Line Items]
Regulatory assets													$ 22				$ 22				22				22
Electricity Generation Plant, Non-Nuclear | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Estimated cost															$ 2,400								$ 2,400
Kemper IGCC - Combined Cycle | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
CIP expenditures incurred but not yet paid																					$ 500
Percentage of costs contracted to third party																					15.00%
Kemper IGCC - Gasification | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
CIP expenditures incurred but not yet paid																					$ 2,800
AFUDC cost																									$ 459
Mine | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Term of management fee contract																								40 years
Scenario, Forecast | Kemper Igcc [Member] | MISSISSIPPI POWER CO | Minimum
Loss Contingencies [Line Items]
Pre-tax charge to income																				$ 100
Scenario, Forecast | Kemper Igcc [Member] | MISSISSIPPI POWER CO | Maximum
Loss Contingencies [Line Items]
Pre-tax charge to income																				$ 200
In-Service Asset Proposal | Kemper Igcc [Member] | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Approved increase (decrease) in fuel rates amount							$ 126	$ 159
Public utilities, approved equity capital structure, percentage							49.733%
Public utilities, approved return on equity percentage							9.225%
Customer refund														$ 11
Denbury Onshore, Contractor | Kemper Igcc [Member] | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Long term contract for purchase of percentage of carbon dioxide captured from plant					100.00%								70.00%				70.00%				70.00%				70.00%
Treetop Midstream Services, LLC, Contractor | Kemper Igcc [Member] | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Long term contract for purchase of percentage of carbon dioxide captured from plant													30.00%				30.00%				30.00%				30.00%
Denbury Onshore, Contractor | Electricity Generation Plant, Non-Nuclear | MISSISSIPPI POWER CO
Loss Contingencies [Line Items]
Long-term contract for purchase of carbon dioxide, term					16 years

Contingencies and Regulatory 42

Contingencies and Regulatory Matters - Current And Actual Cost Estimate (Details) (Details) - MISSISSIPPI POWER CO - USD ($) $ in Millions	Nov. 17, 2016	Apr. 08, 2016	Jun. 30, 2017	Dec. 31, 2012	Jun. 30, 2017
Loss Contingencies [Line Items]
Cost related to grant funding				$ 245
Maximum cap construction cost				2,880
Kemper IGCC
Loss Contingencies [Line Items]
Estimated cost	$ 68		$ 5,680	$ 2,880	$ 2,880
Cost Of Lignite Mine And Equipment			230
Cost Of CO2 Pipeline Facilities			110
Cost Of AFUDC			850
Combined Cycle And Related Assets Placed In Service, Incremental			50
Plant General Exceptions			80
Government grants received		$ (137)
Plant Regulatory Asset			230
Cost related to grant funding			(140)
Maximum cap construction cost			7,090
Deferred costs and other assets			1		1
Project Estimate [Member] | Kemper IGCC
Loss Contingencies [Line Items]
Estimated cost			2,400
Cost Of Lignite Mine And Equipment			210
Cost Of CO2 Pipeline Facilities			140
Cost Of AFUDC			170
Combined Cycle And Related Assets Placed In Service, Incremental			0
Plant General Exceptions			50
Plant Regulatory Asset			0
Cost related to grant funding			0
Maximum cap construction cost			2,970
Current Estimate [Member] | Kemper IGCC
Loss Contingencies [Line Items]
Estimated cost			5,950
Cost Of Lignite Mine And Equipment			230
Cost Of CO2 Pipeline Facilities			110
Cost Of AFUDC			850
Combined Cycle And Related Assets Placed In Service, Incremental			50
Plant General Exceptions			100
Plant Regulatory Asset			230
Cost related to grant funding			(140)
Maximum cap construction cost			7,380
Deferred costs and other assets			$ 33		$ 33

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Assets:
Fair Value	$ 25
Liabilities:
Collateral already posted, aggregate fair value	71
Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	372
Foreign currency derivatives	56
Interest rate derivatives	11
Nuclear decommissioning trusts	1,719
Cash equivalents	834
Other investments	10
Total	3,002
Liabilities:
Energy-related derivatives	366
Interest rate derivatives	23
Foreign currency derivatives	23
Contingent consideration	20
Total	432
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	193
Foreign currency derivatives	0
Interest rate derivatives	0
Nuclear decommissioning trusts	728
Cash equivalents	834
Other investments	9
Total	1,764
Liabilities:
Energy-related derivatives	205
Interest rate derivatives	0
Foreign currency derivatives	0
Contingent consideration	0
Total	205
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	179
Foreign currency derivatives	56
Interest rate derivatives	11
Nuclear decommissioning trusts	966
Cash equivalents	0
Other investments	0
Total	1,212
Liabilities:
Energy-related derivatives	161
Interest rate derivatives	23
Foreign currency derivatives	23
Contingent consideration	0
Total	207
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Foreign currency derivatives	0
Interest rate derivatives	0
Nuclear decommissioning trusts	0
Cash equivalents	0
Other investments	1
Total	1
Liabilities:
Energy-related derivatives	0
Interest rate derivatives	0
Foreign currency derivatives	0
Contingent consideration	20
Total	20
ALABAMA POWER CO
Assets:
Energy-related derivatives	9	$ 20
Fair Value	25
Liabilities:
Energy-related derivatives	11	9
ALABAMA POWER CO | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	9
Cash equivalents	493
Total	1,347
Liabilities:
Energy-related derivatives	11
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Domestic equity
Assets:
Nuclear decommissioning trusts	490
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Foreign equity
Assets:
Nuclear decommissioning trusts	110
ALABAMA POWER CO | Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	29
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Corporate bonds
Assets:
Nuclear decommissioning trusts	167
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	18
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Private Equity
Assets:
Nuclear decommissioning trusts	25
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Other
Assets:
Nuclear decommissioning trusts	6
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	0
Cash equivalents	493
Total	982
Liabilities:
Energy-related derivatives	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Assets:
Nuclear decommissioning trusts	411
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Assets:
Nuclear decommissioning trusts	56
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Assets:
Nuclear decommissioning trusts	22
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private Equity
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	9
Cash equivalents	0
Total	340
Liabilities:
Energy-related derivatives	11
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Assets:
Nuclear decommissioning trusts	79
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Assets:
Nuclear decommissioning trusts	54
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	29
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets:
Nuclear decommissioning trusts	145
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	18
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Private Equity
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other
Assets:
Nuclear decommissioning trusts	6
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Cash equivalents	0
Total	0
Liabilities:
Energy-related derivatives	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Private Equity
Assets:
Nuclear decommissioning trusts	0
ALABAMA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Other
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO
Assets:
Energy-related derivatives	16	46
Nuclear decommissioning trusts	38
Liabilities:
Energy-related derivatives	17	11
GEORGIA POWER CO | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	15
Interest rate derivatives	1
Cash equivalents	50
Total	940
Liabilities:
Energy-related derivatives	14
Interest rate derivatives	3
Total	17
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Domestic equity
Assets:
Nuclear decommissioning trusts	226
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Foreign equity
Assets:
Nuclear decommissioning trusts	147
GEORGIA POWER CO | Fair Value, Measurements, Recurring | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	198
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Corporate bonds
Assets:
Nuclear decommissioning trusts	169
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	41
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Other
Assets:
Nuclear decommissioning trusts	21
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Municipal bonds
Assets:
Nuclear decommissioning trusts	72
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	0
Interest rate derivatives	0
Cash equivalents	50
Total	289
Liabilities:
Energy-related derivatives	0
Interest rate derivatives	0
Total	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity
Assets:
Nuclear decommissioning trusts	225
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Nuclear decommissioning trusts	14
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	15
Interest rate derivatives	1
Cash equivalents	0
Total	651
Liabilities:
Energy-related derivatives	14
Interest rate derivatives	3
Total	17
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity
Assets:
Nuclear decommissioning trusts	1
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity
Assets:
Nuclear decommissioning trusts	147
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	198
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets:
Nuclear decommissioning trusts	169
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	41
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other
Assets:
Nuclear decommissioning trusts	7
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Assets:
Nuclear decommissioning trusts	72
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Interest rate derivatives	0
Cash equivalents	0
Total	0
Liabilities:
Energy-related derivatives	0
Interest rate derivatives	0
Total	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage and asset backed securities
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Other
Assets:
Nuclear decommissioning trusts	0
GEORGIA POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Assets:
Nuclear decommissioning trusts	0
GULF POWER CO
Assets:
Energy-related derivatives	1	5
Liabilities:
Energy-related derivatives	29	29
GULF POWER CO | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	1
Cash equivalents	21
Total	22
Liabilities:
Energy-related derivatives	29
GULF POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	0
Cash equivalents	21
Total	21
Liabilities:
Energy-related derivatives	0
GULF POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	1
Cash equivalents	0
Total	1
Liabilities:
Energy-related derivatives	29
GULF POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Cash equivalents	0
Total	0
Liabilities:
Energy-related derivatives	0
MISSISSIPPI POWER CO
Assets:
Energy-related derivatives	5	7
Liabilities:
Energy-related derivatives	10	11
MISSISSIPPI POWER CO | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	2
Interest rate derivatives	3
Cash equivalents	100
Total	105
Liabilities:
Energy-related derivatives	10
MISSISSIPPI POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	0
Interest rate derivatives	0
Cash equivalents	100
Total	100
Liabilities:
Energy-related derivatives	0
MISSISSIPPI POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	2
Interest rate derivatives	3
Cash equivalents	0
Total	5
Liabilities:
Energy-related derivatives	10
MISSISSIPPI POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Interest rate derivatives	0
Cash equivalents	0
Total	0
Liabilities:
Energy-related derivatives	0
SOUTHERN POWER CO
Assets:
Energy-related derivatives	70	22
Liabilities:
Energy-related derivatives	32	63
SOUTHERN POWER CO | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	14
Foreign currency derivatives	56
Total	70
Liabilities:
Energy-related derivatives	9
Foreign currency derivatives	23
Contingent consideration	20
Total	52
SOUTHERN POWER CO | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	0
Foreign currency derivatives	0
Total	0
Liabilities:
Energy-related derivatives	0
Foreign currency derivatives	0
Contingent consideration	0
Total	0
SOUTHERN POWER CO | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	14
Foreign currency derivatives	56
Total	70
Liabilities:
Energy-related derivatives	9
Foreign currency derivatives	23
Contingent consideration	0
Total	32
SOUTHERN POWER CO | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Foreign currency derivatives	0
Total	0
Liabilities:
Energy-related derivatives	0
Foreign currency derivatives	0
Contingent consideration	20
Total	20
SOUTHERN Co GAS
Assets:
Energy-related derivatives	342	581
Liabilities:
Energy-related derivatives	291	569
Collateral already posted, aggregate fair value	71	$ 62
SOUTHERN Co GAS | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	331
Liabilities:
Energy-related derivatives	291
SOUTHERN Co GAS | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Energy-related derivatives	193
Liabilities:
Energy-related derivatives	205
SOUTHERN Co GAS | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Energy-related derivatives	138
Liabilities:
Energy-related derivatives	86
SOUTHERN Co GAS | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Energy-related derivatives	0
Liabilities:
Energy-related derivatives	0
Nuclear Decommissioning Trusts
Assets:
Fair Value	25
Nuclear Decommissioning Trusts | ALABAMA POWER CO
Assets:
Fair Value	25
Weather Derivative | Fair Value, Measurements, Recurring
Assets:
Energy-related derivatives	$ 11

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 55	$ 47	$ 118	$ 67
Private Equity
Fair Value, Option, Quantitative Disclosures [Line Items]
Liquidations term			10 years
ALABAMA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	28	29	$ 62	40
GEORGIA POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Increase (decrease) in fair value of funds	$ 27	$ 18	$ 56	$ 27
Minimum | SOUTHERN POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent payment obligations, payment period			10 years
Maximum | SOUTHERN POWER CO
Fair Value, Option, Quantitative Disclosures [Line Items]
Contingent payment obligations, payment period			30 years

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Measurements Of Investments Calculated At Net Asset Value Per Share (Details) $ in Millions	Jun. 30, 2017USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 25
Private Equity
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	25
Unfunded Commitments	22
ALABAMA POWER CO
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	25
ALABAMA POWER CO | Private Equity
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	25
Unfunded Commitments	$ 22

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions	Jun. 30, 2017USD ($)
Southern Company
Long-term debt:
Carrying Amount	$ 46,631
Fair Value	48,228
ALABAMA POWER CO
Long-term debt:
Carrying Amount	7,440
Fair Value	8,041
GEORGIA POWER CO
Long-term debt:
Carrying Amount	10,888
Fair Value	11,585
GULF POWER CO
Long-term debt:
Carrying Amount	1,292
Fair Value	1,336
MISSISSIPPI POWER CO
Long-term debt:
Carrying Amount	2,125
Fair Value	2,071
SOUTHERN POWER CO
Long-term debt:
Carrying Amount	5,725
Fair Value	5,878
SOUTHERN Co GAS
Long-term debt:
Carrying Amount	5,699
Fair Value	$ 6,031

Stockholders' Equity - Earnings

Stockholders' Equity - Earnings per Share (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
As reported shares (in shares)	998	934	996	925
Effect of options and performance share award units (in shares)	7	6	7	6
Diluted shares (in shares)	1,005	940	1,003	931
Stock options and performance share award units that were not included in the diluted earnings per share calculation (in shares)	0	0	0	0

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)				(800)
Beginning balance				$ 26,612	$ 21,982
Consolidated net income (loss) attributable to Southern Company		$ (1,381)	$ 623	(723)	1,112
Other comprehensive income (loss)				(11)	(117)
Stock issued				417	1,383
Stock-based compensation				72	67
Cash dividends on common stock				(1,134)	(1,023)
Preference stock redemption				(150)
Contributions from noncontrolling interests				71	169
Distributions to noncontrolling interests				(40)	(10)
Purchase of membership interests from noncontrolling interests					(129)
Net income attributable to noncontrolling interests				16	11
Reclassification from redeemable noncontrolling interests				114
Other				$ (3)	1
Ending balance, treasury shares (in shares)		(900)		(900)
Ending balance		$ 25,241	$ 23,446	$ 25,241	$ 23,446
Number of Common Shares Issued
Changes in Stockholders' Equity
Beginning balance (in shares)				991,213	915,073
Stock issued (in shares)				9,129	27,297
Other (in shares)				0
Ending balance (in shares)		1,000,342	942,370	1,000,342	942,370
Number of Common Shares Treasury Issued
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)				(819)	(3,352)
Stock issued (in shares)				0	2,599
Other (in shares)				(49)	(19)
Ending balance, treasury shares (in shares)		(868)	(772)	(868)	(772)
Common Stockholders' Equity
Changes in Stockholders' Equity
Beginning balance				$ 24,758	$ 20,592
Consolidated net income (loss) attributable to Southern Company				(723)	1,112
Other comprehensive income (loss)				(11)	(117)
Stock issued				417	1,383
Stock-based compensation				72	67
Cash dividends on common stock				(1,134)	(1,023)
Other				(7)	1
Ending balance		$ 23,372	$ 22,015	23,372	22,015
Preferred and Preference Stock of Subsidiaries
Changes in Stockholders' Equity
Beginning balance				609	609
Preference stock redemption				(150)
Other				3
Ending balance		462	609	462	609
Noncontrolling Interest
Changes in Stockholders' Equity
Beginning balance				1,245	781
Contributions from noncontrolling interests				71	169
Distributions to noncontrolling interests				(40)	(10)
Purchase of membership interests from noncontrolling interests					(129)
Net income attributable to noncontrolling interests				16	11
Reclassification from redeemable noncontrolling interests				114
Other				1
Ending balance		$ 1,407	$ 822	$ 1,407	$ 822
SunPower Corp. | Noncontrolling Interest
Changes in Stockholders' Equity
Beginning balance	$ 114

Financing - Narrative (Details)

Financing - Narrative (Details) shares in Thousands	Jun. 30, 2017USD ($)	Jun. 03, 2015USD ($)	Feb. 20, 2014	Jun. 30, 2017USD ($)agreement	May 31, 2017USD ($)shares	Apr. 30, 2017USD ($)	Feb. 28, 2017USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Short-term debt	$ 3,274,000,000			$ 3,274,000,000				$ 3,274,000,000			$ 2,241,000,000
Variable rate pollution control revenue bonds outstanding	1,600,000,000			1,600,000,000				1,600,000,000
Maximum borrowing capacity	8,168,000,000			8,168,000,000				8,168,000,000
Senior Note Issuances								2,450,000,000
Preference stock redemption								150,000,000
Southern Company
Debt Instrument [Line Items]
Maximum borrowing capacity	2,000,000,000			2,000,000,000	$ 1,250,000,000			2,000,000,000
Senior Note Issuances								300,000,000
Southern Company | Senior Notes | Series 2017A
Debt Instrument [Line Items]
Debt face amount	$ 500,000,000			$ 500,000,000				$ 500,000,000
Debt stated interest rate	5.325%			5.325%				5.325%
Southern Company | Senior Notes | Series 2017A Floating Rate Senior Notes
Debt Instrument [Line Items]
Debt face amount	$ 300,000,000			$ 300,000,000				$ 300,000,000
Southern Company | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement
Debt Instrument [Line Items]
Number of loan agreements | agreement				2
Southern Company | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement 4
Debt Instrument [Line Items]
Debt face amount	100,000,000			$ 100,000,000				100,000,000
Southern Company | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement 5
Debt Instrument [Line Items]
Debt face amount	100,000,000			100,000,000				100,000,000
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Working capital	930,000,000			930,000,000				930,000,000
Senior notes, current	17,000,000			17,000,000				17,000,000
Short-term debt	17,000,000			17,000,000				17,000,000			23,000,000
Long-term pollution control bond	50,000,000			50,000,000				50,000,000
Variable rate pollution control revenue bonds outstanding	40,000,000			40,000,000				40,000,000
Fixed rate pollution control revenue bonds outstanding	50,000,000			50,000,000				50,000,000
Maximum borrowing capacity	113,000,000			113,000,000				113,000,000
Senior Note Issuances								0
Promissory note		$ 301,000,000
Capital contributions from parent company	1,000,000,000							1,001,000,000	$ 226,000,000
MISSISSIPPI POWER CO | Unsecured Debt
Debt Instrument [Line Items]
Loans payable to bank	935,000,000			935,000,000				935,000,000
MISSISSIPPI POWER CO | Tax-Exempt Variable Rate Demand Obligations
Debt Instrument [Line Items]
Short-term debt	40,000,000			40,000,000				40,000,000
MISSISSIPPI POWER CO | Short Term Note
Debt Instrument [Line Items]
Debt face amount										$ 9,000,000
Debt stated interest rate										5.00%
MISSISSIPPI POWER CO | Bank Loans | Loans Payable [Member]
Debt Instrument [Line Items]
Repayments of debt				10,000,000
MISSISSIPPI POWER CO | Promissory Notes | Promissory Notes
Debt Instrument [Line Items]
Repayments of debt				591,000,000
Increase in debt instrument						$ 40,000,000
MISSISSIPPI POWER CO | Unsecured Debt | Term Loan
Debt Instrument [Line Items]
Debt face amount	1,200,000,000			1,200,000,000				1,200,000,000
Repayments of debt				300,000,000
GEORGIA POWER CO
Debt Instrument [Line Items]
Short-term debt	1,228,000,000			1,228,000,000				1,228,000,000			391,000,000
Debt instrument, basis spread on variable rate			0.375%
Amortization period for line of credit facility			5 years
Variable rate pollution control revenue bonds outstanding	550,000,000			550,000,000				550,000,000
Variable rate pollution control revenue bonds outstanding, amount remarketed	318,000,000			318,000,000				318,000,000
Fixed rate pollution control revenue bonds outstanding	436,000,000			436,000,000				436,000,000
Maximum borrowing capacity	1,750,000,000			1,750,000,000				1,750,000,000
Senior Note Issuances								850,000,000
Capital contributions from parent company								380,000,000	239,000,000
GEORGIA POWER CO | Line of Credit | Uncommitted Bank Credit Arrangement
Debt Instrument [Line Items]
Increase in debt instrument				$ 500,000,000
GEORGIA POWER CO | Senior Notes | Series 2017A
Debt Instrument [Line Items]
Debt face amount										$ 450,000,000
Debt stated interest rate										2.00%
GEORGIA POWER CO | Senior Notes | Series 2017B
Debt Instrument [Line Items]
Debt face amount										$ 400,000,000
Debt stated interest rate										3.25%
GEORGIA POWER CO | Municipal Bonds [Member] | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1995
Debt Instrument [Line Items]
Debt face amount						$ 27,000,000
GEORGIA POWER CO | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement
Debt Instrument [Line Items]
Number of loan agreements | agreement				3
Payable to bank by demand, term				30 days
GEORGIA POWER CO | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement 1
Debt Instrument [Line Items]
Debt face amount	50,000,000			$ 50,000,000				50,000,000
GEORGIA POWER CO | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement 2
Debt Instrument [Line Items]
Debt face amount	150,000,000			150,000,000				150,000,000
GEORGIA POWER CO | Notes Payable to Banks | Floating Rate Bank Term Loan Agreement 3
Debt Instrument [Line Items]
Debt face amount	100,000,000			100,000,000				100,000,000
ALABAMA POWER CO
Debt Instrument [Line Items]
Variable rate pollution control revenue bonds outstanding	890,000,000			890,000,000				890,000,000
Maximum borrowing capacity	1,335,000,000			1,335,000,000				1,335,000,000
Senior Note Issuances								550,000,000
Capital contributions from parent company								327,000,000	237,000,000
ALABAMA POWER CO | Senior Notes | Series 2017A
Debt Instrument [Line Items]
Debt face amount	$ 550,000,000			$ 550,000,000				$ 550,000,000
Debt stated interest rate	2.45%			2.45%				2.45%
GULF POWER CO
Debt Instrument [Line Items]
Short-term debt	$ 78,000,000			$ 78,000,000				$ 78,000,000			268,000,000
Variable rate pollution control revenue bonds outstanding	82,000,000			82,000,000				82,000,000
Fixed rate pollution control revenue bonds outstanding	140,000,000			140,000,000				140,000,000
Maximum borrowing capacity	280,000,000			280,000,000				280,000,000
Senior Note Issuances								300,000,000
Capital contributions from parent company								5,000,000	5,000,000
GULF POWER CO | Senior Notes | Series 2017A
Debt Instrument [Line Items]
Debt face amount					$ 300,000,000
Debt stated interest rate					3.30%
GULF POWER CO | Senior Notes | Series 2007A
Debt Instrument [Line Items]
Debt stated interest rate					5.90%
Repayments of debt					$ 85,000,000
GULF POWER CO | Senior Notes | Series Preference Stock
Debt Instrument [Line Items]
Debt stated interest rate					6.00%
Stock redeemed during period (in shares) | shares					550
Preference stock redemption					$ 55,000,000
GULF POWER CO | Senior Notes | Series 2007A Preference Stock
Debt Instrument [Line Items]
Debt stated interest rate					6.45%
Stock redeemed during period (in shares) | shares					450
Preference stock redemption					$ 45,000,000
GULF POWER CO | Senior Notes | Series 2013A Preference Stock
Debt Instrument [Line Items]
Debt stated interest rate					5.60%
Stock redeemed during period (in shares) | shares					500
Preference stock redemption					$ 50,000,000
GULF POWER CO | Senior Notes | Short-term Floating Rate Bank Loan
Debt Instrument [Line Items]
Repayments of debt					100,000,000
GULF POWER CO | Bank Loans
Debt Instrument [Line Items]
Debt face amount										$ 100,000,000
Traditional Electric Operating Companies
Debt Instrument [Line Items]
Fixed rate pollution control revenue bonds outstanding	626,000,000			626,000,000				626,000,000
SOUTHERN POWER CO
Debt Instrument [Line Items]
Short-term debt	398,000,000			398,000,000				398,000,000			209,000,000
Maximum borrowing capacity	750,000,000			750,000,000	600,000,000			750,000,000
Senior Note Issuances								0
Capital contributions from parent company								0	$ 300,000,000
Southern Company Gas Capital
Debt Instrument [Line Items]
Maximum borrowing capacity	1,200,000,000			1,200,000,000	1,200,000,000			1,200,000,000
Nicor Gas
Debt Instrument [Line Items]
Maximum borrowing capacity	700,000,000			700,000,000	700,000,000			700,000,000
SOUTHERN Co GAS
Debt Instrument [Line Items]
Short-term debt	626,000,000			626,000,000				626,000,000			$ 1,257,000,000
Maximum borrowing capacity	$ 1,900,000,000			$ 1,900,000,000				1,900,000,000
Senior Note Issuances								450,000,000
Capital contributions from parent company								$ 57,000,000
SOUTHERN Co GAS | Senior Notes | Series 2017A
Debt Instrument [Line Items]
Debt face amount					$ 450,000,000
Debt stated interest rate					4.40%
Southern Company | MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Promissory note							$ 551,000,000
Line of Credit | Southern Company | Line of Credit
Debt Instrument [Line Items]
Extinguishment of debt, amount					$ 1,000,000,000
Line of Credit | Southern Company Gas Capital
Debt Instrument [Line Items]
Termination of Credit Arrangement					1,300,000,000
Line of Credit | Nicor Gas | Line of Credit
Debt Instrument [Line Items]
Termination of Credit Arrangement					$ 700,000,000

Financing - Schedule of Credit

Financing - Schedule of Credit Arrangements (Details) - USD ($)	Jun. 30, 2017	May 31, 2017
Line of Credit Facility [Line Items]
Expires, 2017	$ 156,000,000
Expires, 2018	757,000,000
Expires, 2019	25,000,000
Expires, 2020	30,000,000
Expires, 2022	7,200,000,000
Total	8,168,000,000
Unused	8,011,000,000
Executable Term Loans, One Year	65,000,000
Executable Term Loans, Two Years	13,000,000
Expires Within One Year, Term Out	33,000,000
Expires Within One Year, No Term Out	195,000,000
Southern Company
Line of Credit Facility [Line Items]
Expires, 2017	0
Expires, 2018	0
Expires, 2019	0
Expires, 2020	0
Expires, 2022	2,000,000,000
Total	2,000,000,000	$ 1,250,000,000
Unused	2,000,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	0
ALABAMA POWER CO
Line of Credit Facility [Line Items]
Expires, 2017	3,000,000
Expires, 2018	532,000,000
Expires, 2019	0
Expires, 2020	0
Expires, 2022	800,000,000
Total	1,335,000,000
Unused	1,335,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	35,000,000
GEORGIA POWER CO
Line of Credit Facility [Line Items]
Expires, 2017	0
Expires, 2018	0
Expires, 2019	0
Expires, 2020	0
Expires, 2022	1,750,000,000
Total	1,750,000,000
Unused	1,732,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	0
GULF POWER CO
Line of Credit Facility [Line Items]
Expires, 2017	30,000,000
Expires, 2018	195,000,000
Expires, 2019	25,000,000
Expires, 2020	30,000,000
Expires, 2022	0
Total	280,000,000
Unused	280,000,000
Executable Term Loans, One Year	45,000,000
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	40,000,000
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
Expires, 2017	113,000,000
Expires, 2018	0
Expires, 2019	0
Expires, 2020	0
Expires, 2022	0
Total	113,000,000
Unused	100,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	13,000,000
Expires Within One Year, Term Out	13,000,000
Expires Within One Year, No Term Out	100,000,000
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
Expires, 2017	0
Expires, 2018	0
Expires, 2019	0
Expires, 2020	0
Expires, 2022	750,000,000
Total	750,000,000	600,000,000
Unused	675,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	0
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
Expires, 2017	0
Expires, 2018	0
Expires, 2019	0
Expires, 2020	0
Expires, 2022	1,900,000,000
Total	1,900,000,000
Unused	1,849,000,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	0
Expires Within One Year, No Term Out	0
Other [Member]
Line of Credit Facility [Line Items]
Expires, 2017	10,000,000
Expires, 2018	30,000,000
Expires, 2019	0
Expires, 2020	0
Expires, 2022	0
Total	40,000,000
Unused	40,000,000
Executable Term Loans, One Year	20,000,000
Executable Term Loans, Two Years	0
Expires Within One Year, Term Out	20,000,000
Expires Within One Year, No Term Out	20,000,000
Southern Company Gas Capital
Line of Credit Facility [Line Items]
Total	1,200,000,000	1,200,000,000
Nicor Gas
Line of Credit Facility [Line Items]
Total	$ 700,000,000	$ 700,000,000

Financing - Schedule of Long-Te

Financing - Schedule of Long-Term Debt Financing Activities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Debt Instrument [Line Items]
Senior Note Issuances	$ 2,450
Senior Note Maturities and Redemptions	735
Revenue Bond Maturities, Redemptions, and Repurchases	27
Other Long-Term Debt Issuances	509
Other Long-Term Debt Redemptions and Maturities	716
Southern Company
Debt Instrument [Line Items]
Senior Note Issuances	300
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	500
Other Long-Term Debt Redemptions and Maturities	400
ALABAMA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	550
Senior Note Maturities and Redemptions	200
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
GEORGIA POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	850
Senior Note Maturities and Redemptions	450
Revenue Bond Maturities, Redemptions, and Repurchases	27
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	3
GULF POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	300
Senior Note Maturities and Redemptions	85
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	6
Other Long-Term Debt Redemptions and Maturities	0
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	40
Other Long-Term Debt Redemptions and Maturities	893
SOUTHERN POWER CO
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	3
Other Long-Term Debt Redemptions and Maturities	3
SOUTHERN Co GAS
Debt Instrument [Line Items]
Senior Note Issuances	450
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	0
Other [Member]
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	0
Other Long-Term Debt Redemptions and Maturities	8
Consolidation Eliminations
Debt Instrument [Line Items]
Senior Note Issuances	0
Senior Note Maturities and Redemptions	0
Revenue Bond Maturities, Redemptions, and Repurchases	0
Other Long-Term Debt Issuances	(40)
Other Long-Term Debt Redemptions and Maturities	$ (591)

Retirement Benefits (Details)

Retirement Benefits (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 0		$ 0
Pension Plans | Southern Company
Pension Plans and Postretirement Plans
Service cost	74,000,000	$ 62,000,000	147,000,000	$ 124,000,000
Interest cost	113,000,000	101,000,000	227,000,000	201,000,000
Expected return on plan assets	(225,000,000)	(187,000,000)	(449,000,000)	(374,000,000)
Amortization:
Prior service costs	3,000,000	3,000,000	6,000,000	7,000,000
Net (gain)/loss	41,000,000	37,000,000	81,000,000	75,000,000
Net periodic pension cost (income)	6,000,000	16,000,000	12,000,000	33,000,000
Pension Plans | SOUTHERN Co GAS
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	5,000,000		11,000,000
Interest cost	10,000,000		20,000,000
Expected return on plan assets	(17,000,000)		(35,000,000)
Amortization:
Prior service costs	(1,000,000)		(1,000,000)
Net (gain)/loss	5,000,000		10,000,000
Net periodic pension cost (income)	2,000,000		5,000,000
Pension Plans | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	16,000,000	15,000,000	32,000,000	29,000,000
Interest cost	24,000,000	24,000,000	48,000,000	48,000,000
Expected return on plan assets	(49,000,000)	(46,000,000)	(98,000,000)	(92,000,000)
Amortization:
Prior service costs	0	0	1,000,000	1,000,000
Net (gain)/loss	11,000,000	10,000,000	21,000,000	20,000,000
Net periodic pension cost (income)	2,000,000	3,000,000	4,000,000	6,000,000
Pension Plans | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	18,000,000	18,000,000	37,000,000	35,000,000
Interest cost	35,000,000	34,000,000	69,000,000	68,000,000
Expected return on plan assets	(70,000,000)	(65,000,000)	(141,000,000)	(129,000,000)
Amortization:
Prior service costs	1,000,000	2,000,000	2,000,000	3,000,000
Net (gain)/loss	14,000,000	13,000,000	28,000,000	27,000,000
Net periodic pension cost (income)	(2,000,000)	2,000,000	(5,000,000)	4,000,000
Pension Plans | GULF POWER CO
Pension Plans and Postretirement Plans
Service cost	4,000,000	3,000,000	7,000,000	6,000,000
Interest cost	5,000,000	4,000,000	10,000,000	9,000,000
Expected return on plan assets	(9,000,000)	(8,000,000)	(19,000,000)	(17,000,000)
Amortization:
Prior service costs	0	1,000,000	0	1,000,000
Net (gain)/loss	1,000,000	1,000,000	3,000,000	3,000,000
Net periodic pension cost (income)	1,000,000	1,000,000	1,000,000	2,000,000
Pension Plans | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	3,000,000	3,000,000	7,000,000	6,000,000
Interest cost	5,000,000	5,000,000	10,000,000	10,000,000
Expected return on plan assets	(10,000,000)	(8,000,000)	(20,000,000)	(17,000,000)
Amortization:
Prior service costs	1,000,000	0	1,000,000	0
Net (gain)/loss	2,000,000	1,000,000	4,000,000	3,000,000
Net periodic pension cost (income)	1,000,000	1,000,000	2,000,000	2,000,000
Postretirement Benefits | Southern Company
Pension Plans and Postretirement Plans
Service cost	6,000,000	6,000,000	12,000,000	11,000,000
Interest cost	20,000,000	17,000,000	40,000,000	35,000,000
Expected return on plan assets	(17,000,000)	(14,000,000)	(33,000,000)	(28,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	3,000,000	3,000,000
Net (gain)/loss	5,000,000	4,000,000	7,000,000	7,000,000
Net periodic pension cost (income)	15,000,000	14,000,000	29,000,000	28,000,000
Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost	0		1,000,000
Interest cost	2,000,000		5,000,000
Expected return on plan assets	(1,000,000)		(3,000,000)
Amortization:
Prior service costs	0		(1,000,000)
Net (gain)/loss	1,000,000		2,000,000
Net periodic pension cost (income)	2,000,000		4,000,000
Postretirement Benefits | ALABAMA POWER CO
Pension Plans and Postretirement Plans
Service cost	2,000,000	2,000,000	3,000,000	3,000,000
Interest cost	4,000,000	4,000,000	9,000,000	9,000,000
Expected return on plan assets	(8,000,000)	(7,000,000)	(14,000,000)	(13,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	2,000,000	2,000,000
Net (gain)/loss	1,000,000	1,000,000	1,000,000	1,000,000
Net periodic pension cost (income)	0	1,000,000	1,000,000	2,000,000
Postretirement Benefits | GEORGIA POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	3,000,000	3,000,000
Interest cost	8,000,000	7,000,000	15,000,000	15,000,000
Expected return on plan assets	(6,000,000)	(5,000,000)	(12,000,000)	(11,000,000)
Amortization:
Prior service costs	1,000,000	1,000,000	1,000,000	1,000,000
Net (gain)/loss	1,000,000	2,000,000	3,000,000	4,000,000
Net periodic pension cost (income)	5,000,000	6,000,000	10,000,000	12,000,000
Postretirement Benefits | GULF POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	1,000,000	1,000,000
Interest cost	0	0	1,000,000	1,000,000
Expected return on plan assets	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	0	0	1,000,000	1,000,000
Postretirement Benefits | MISSISSIPPI POWER CO
Pension Plans and Postretirement Plans
Service cost	1,000,000	1,000,000	1,000,000	1,000,000
Interest cost	1,000,000	1,000,000	2,000,000	2,000,000
Expected return on plan assets	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Amortization:
Prior service costs	0	0	0	0
Net (gain)/loss	0	0	0	0
Net periodic pension cost (income)	$ 1,000,000	1,000,000	$ 2,000,000	2,000,000
Predecessor | Pension Plans | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost		7,000,000		13,000,000
Interest cost		11,000,000		21,000,000
Expected return on plan assets		(17,000,000)		(33,000,000)
Amortization:
Prior service costs		(1,000,000)		(1,000,000)
Net (gain)/loss		7,000,000		13,000,000
Net periodic pension cost (income)		7,000,000		13,000,000
Predecessor | Postretirement Benefits | SOUTHERN Co GAS
Pension Plans and Postretirement Plans
Service cost		0		1,000,000
Interest cost		2,000,000		5,000,000
Expected return on plan assets		(1,000,000)		(3,000,000)
Amortization:
Prior service costs		0		(1,000,000)
Net (gain)/loss		1,000,000		2,000,000
Net periodic pension cost (income)		$ 2,000,000		$ 4,000,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			$ 81	$ 21
Effective tax rate	(28.60%)	29.40%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2016	$ 484
Tax positions from current periods	10
Tax positions from prior periods	7
Balance as of June 30, 2017	501
Tax positions impacting the effective tax rate			37	20
Tax positions not impacting the effective tax rate			464	464
Balance of unrecognized tax benefits	$ 484		501	484
Significantly increase (decrease) in amount of unrecognized tax benefits	12 months
Kemper IGCC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of June 30, 2017	$ 464
Balance of unrecognized tax benefits	$ 464		464
Unrecognized tax benefit, associated interest			36
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			19
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			46
Effective tax rate	(30.50%)	(208.10%)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2016	$ 465
Tax positions from current periods	3
Tax positions from prior periods	0
Balance as of June 30, 2017	468
Tax positions impacting the effective tax rate			4
Tax positions not impacting the effective tax rate			464
Balance of unrecognized tax benefits	465		468	465
MISSISSIPPI POWER CO | Kemper IGCC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of June 30, 2017	464
Balance of unrecognized tax benefits	$ 464		464
Unrecognized tax benefit, associated interest			36
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax rate	(114.70%)	(74.00%)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits as of December 31, 2016	$ 17
Tax positions from current periods	1
Tax positions from prior periods	1
Balance as of June 30, 2017	19
Tax positions impacting the effective tax rate			19
Tax positions not impacting the effective tax rate			0
Balance of unrecognized tax benefits	$ 17		19	17
Investment Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, amount			1,900	$ 1,800
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Tax positions not impacting the effective tax rate			98
Federal
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			18
Federal | SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			18
Federal | MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			0
State (net of federal benefit)
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			63
State (net of federal benefit) | SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			1
State (net of federal benefit) | MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance			$ 46

Derivatives - Energy-Related an

Derivatives - Energy-Related and Interest Rate Derivatives (Details) BTU in Millions, $ in Millions, MMBTU in Billions	6 Months Ended
	Jun. 30, 2017USD ($)MMBTUBTU
Interest Rate Contract
Interest rate derivatives
Notional Amount	$ 3,900
Fair Value Gain (Loss) at June 30, 2017	$ (11)
Southern Company | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	472
Longest Hedge Date	2,021
Longest Non-Hedge Date	2,024
Southern Company | Interest Rate Contract | 2017-08-01 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 250
Interest Rate Received	1.30%
Fair Value Gain (Loss) at June 30, 2017	$ 0
Southern Company | Interest Rate Contract | 2017-08-01 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.17%
Southern Company | Interest Rate Contract | 2020-06-01 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 300
Interest Rate Received	2.75%
Fair Value Gain (Loss) at June 30, 2017	$ 1
Southern Company | Interest Rate Contract | 2020-06-01 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.92%
Southern Company | Interest Rate Contract | 7/31/2021 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 1,500
Interest Rate Received	2.35%
Fair Value Gain (Loss) at June 30, 2017	$ (14)
Southern Company | Interest Rate Contract | 7/31/2021 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.87%
ALABAMA POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	70
Longest Hedge Date	2,020
GEORGIA POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	160
Longest Hedge Date	2,020
GEORGIA POWER CO | Interest Rate Contract | 6/1/2018 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 250
Interest Rate Received	5.40%
Fair Value Gain (Loss) at June 30, 2017	$ 0
GEORGIA POWER CO | Interest Rate Contract | 6/1/2018 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	4.02%
GEORGIA POWER CO | Interest Rate Contract | 12/1/2018 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 500
Interest Rate Received	1.95%
Fair Value Gain (Loss) at June 30, 2017	$ (2)
GEORGIA POWER CO | Interest Rate Contract | 12/1/2018 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	0.76%
GEORGIA POWER CO | Interest Rate Contract | 12/1/2019 | Fair Value Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 200
Interest Rate Received	4.25%
Fair Value Gain (Loss) at June 30, 2017	$ 1
GEORGIA POWER CO | Interest Rate Contract | 12/1/2019 | London Interbank Offered Rate (LIBOR) | Fair Value Hedges of Existing Debt
Interest rate derivatives
Weighted Average Interest Rate Paid	2.46%
GULF POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	35
Longest Hedge Date	2,020
MISSISSIPPI POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	41
Longest Hedge Date	2,021
MISSISSIPPI POWER CO | Interest Rate Contract | 3/1/2018 | Cash Flow Hedges of Existing Debt
Interest rate derivatives
Notional Amount	$ 900
Weighted Average Interest Rate Paid	0.79%
Fair Value Gain (Loss) at June 30, 2017	$ 3
SOUTHERN POWER CO | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	25
Longest Hedge Date	2,017
SOUTHERN Co GAS | Energy-related, Natural Gas
Energy-related derivative contracts
Net Purchased mmBtu | BTU	141
Longest Hedge Date	2,019
Longest Non-Hedge Date	2,024
SOUTHERN Co GAS | Energy-related, Natural Gas | Long | Derivatives not designated as hedging instruments
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume | MMBTU	3.5
SOUTHERN Co GAS | Energy-related, Natural Gas | Short | Derivatives not designated as hedging instruments
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume | MMBTU	3.4

Derivatives - Narrative (Detail

Derivatives - Narrative (Details) MMBTU in Millions	6 Months Ended
	Jun. 30, 2017USD ($)MMBTU	Dec. 31, 2016USD ($)
Derivative [Line Items]
Collateral already posted, aggregate fair value	$ 71,000,000
Maximum potential collateral requirements arising from credit risk related contingent features	$ 11,000,000
Southern Company
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	31
Cash flow hedge gain (loss) to be reclassified within twelve months	$ (21,000,000)
GEORGIA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	10
SOUTHERN POWER CO
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 6,000,000
Gulf Power and Mississippi Power [Member]
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	3
ALABAMA POWER CO
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU	5
Parent Company and Southern Power
Derivative [Line Items]
Foreign currency cash flow hedge gain (loss) to be reclassified during next 12 months	$ (23,000,000)
SOUTHERN Co GAS
Derivative [Line Items]
Collateral already posted, aggregate fair value	71,000,000	$ 62,000,000
Maximum potential collateral requirements arising from credit risk related contingent features	1,000,000
Traditional Operating Companies and Southern Power
Derivative [Line Items]
Maximum potential collateral requirements arising from credit risk related contingent features	10,000,000
Derivative Counterparties | Registrants
Derivative [Line Items]
Collateral already posted, aggregate fair value	$ 0

Derivatives - Foreign Currency

Derivatives - Foreign Currency Derivatives (Details) - 6 months ended Jun. 30, 2017 - Cash Flow Hedges of Existing Debt - Foreign Exchange Contract € in Millions, $ in Millions	USD ($)	EUR (€)
Derivative [Line Items]
Pay Notional	$ 1,241
Receive Notional | €		€ 1,100
Fair Value Gain (Loss) at June 30, 2017	33
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 June 30, 2017	$ 18
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 June 30, 2017	$ 15

Derivatives - Derivative Financ

Derivatives - Derivative Financial Statement Presentation and Amounts With Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Collateral already posted, aggregate fair value	$ 71
Southern Company
Derivatives, Fair Value [Line Items]
Derivatives, assets	450	$ 690
Derivatives, liabilities	410	718
Derivative asset amount offset	(219)	(462)
Derivative liability amount offset	(290)	(524)
Derivative asset	231	228
Derivative liability	120	194
Southern Company | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	339	556
Derivatives, liabilities	288	564
Southern Company | Derivatives not designated as hedging instruments | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	237	489
Southern Company | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	102	66
Southern Company | Derivatives not designated as hedging instruments | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	202	483
Southern Company | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	86	81
Southern Company | Derivatives not designated as hedging instruments | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
Southern Company | Derivatives not designated as hedging instruments | Interest rate derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
Southern Company | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives
Derivatives, Fair Value [Line Items]
Derivatives, assets	31	98
Derivatives, liabilities	66	60
Southern Company | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	23	73
Southern Company | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	8	25
Southern Company | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	35	27
Southern Company | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	31	33
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	80	36
Derivatives, liabilities	56	94
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	13	23
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	10	7
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	11	12
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	1
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	22	28
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	0
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	56	0
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	33
Southern Company | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	23	25
ALABAMA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	9	20
Derivatives, liabilities	11	9
Derivative asset amount offset	(6)	(8)
Derivative liability amount offset	(6)	(8)
Derivative asset	3	12
Derivative liability	5	1
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	9	20
Derivatives, liabilities	11	9
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	7	13
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	7
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	7	5
ALABAMA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	4
GEORGIA POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	16	46
Derivatives, liabilities	17	11
Derivative asset amount offset	(9)	(8)
Derivative liability amount offset	(9)	(8)
Derivative asset	7	38
Derivative liability	8	3
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	15	44
Derivatives, liabilities	14	8
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	10	30
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	14
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	10	7
GEORGIA POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	1
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
Derivatives, liabilities	3	3
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other deferred charges and 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 | Designated as Hedging Instrument | Interest rate derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	3
GEORGIA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	0
GULF POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	5
Derivatives, liabilities	29	29
Derivative asset amount offset	(1)	(4)
Derivative liability amount offset	(1)	(4)
Derivative asset	0	1
Derivative liability	28	25
GULF POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	5
Derivatives, liabilities	29	29
GULF POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	4
GULF POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
GULF POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	16	12
GULF POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	13	17
MISSISSIPPI POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	5	7
Derivatives, liabilities	10	11
Derivative asset amount offset	(2)	(3)
Derivative liability amount offset	(2)	(3)
Derivative asset	3	4
Derivative liability	8	8
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	2	4
Derivatives, liabilities	10	11
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	2
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	4	5
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	6	6
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	3	3
Derivatives, liabilities	0	0
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	3	2
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
MISSISSIPPI POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Interest rate derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN POWER CO
Derivatives, Fair Value [Line Items]
Derivatives, assets	70	22
Derivatives, liabilities	32	63
Derivative asset amount offset	(2)	(5)
Derivative liability amount offset	(2)	(5)
Derivative asset	68	17
Derivative liability	30	58
SOUTHERN POWER CO | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	4
Derivatives, liabilities	1	1
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	1	3
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	1	1
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Interest rate derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
SOUTHERN POWER CO | Derivatives not designated as hedging instruments | Interest rate derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivatives, assets	69	18
Derivatives, liabilities	31	62
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	13	18
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	8	4
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | 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 | Designated as Hedging Instrument | Foreign currency derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	56	0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	33
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Foreign currency derivatives | Other current liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	23	25
SOUTHERN Co GAS
Derivatives, Fair Value [Line Items]
Derivatives, assets	342	581
Derivatives, liabilities	291	569
Derivative asset amount offset	(196)	(435)
Derivative liability amount offset	(267)	(497)
Derivative asset	146	146
Derivative liability	24	72
Collateral already posted, aggregate fair value	71	62
SOUTHERN Co GAS | Energy-related derivatives
Derivatives, Fair Value [Line Items]
Collateral already posted, aggregate fair value	1	8
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives
Derivatives, Fair Value [Line Items]
Derivatives, assets	338	552
Derivatives, liabilities	287	563
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	102	66
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	86	81
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Assets From Risk Management Activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	236	486
SOUTHERN Co GAS | Derivatives not designated as hedging instruments | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	201	482
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives
Derivatives, Fair Value [Line Items]
Derivatives, assets	4	25
Derivatives, liabilities	2	3
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred charges and assets
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	1
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Other deferred credits and liabilities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	0	0
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Assets From Risk Management Activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	4	24
SOUTHERN Co GAS | Derivatives designated as hedging instruments for regulatory purposes | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	2	3
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Assets From Risk Management Activities
Derivatives, Fair Value [Line Items]
Derivatives, assets	0	4
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Designated as Hedging Instrument | Energy-related derivatives | Liabilities from risk management activities
Derivatives, Fair Value [Line Items]
Derivatives, liabilities	$ 2	$ 3

Derivatives - Pre-tax Effects o

Derivatives - Pre-tax Effects of Derivatives Designated as Cash Flow Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	$ 71		$ 71
Southern Company
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	61	$ (33)	46	$ (223)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	67	(25)	68	(28)
Southern Company | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(34)		(34)		$ 33
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(9)	0	(20)	0
Southern Company | Energy-related derivatives | Depreciation and amortization
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(2)	0	(6)	0
Southern Company | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(24)		(24)		(16)
Southern Company | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(23)		(23)		(19)
Southern Company | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	13		13		56
Southern Company | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					12
Southern Company | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(1)	6	(1)	(184)
Southern Company | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(5)	(4)	(10)	(7)
Southern Company | Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	71	(39)	67	(39)
Southern Company | Foreign Exchange Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(5)	(1)	(12)	(1)
Southern Company | Foreign Exchange Contract | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	79	(20)	96	(20)
ALABAMA POWER CO | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(2)		(2)		11
ALABAMA POWER CO | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(3)		(3)		(1)
ALABAMA POWER CO | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(2)		(2)		0
ALABAMA POWER CO | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	3		3		8
ALABAMA POWER CO | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					4
ALABAMA POWER CO | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	0	(4)
ALABAMA POWER CO | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(2)	(2)	(3)	(3)
GEORGIA POWER CO | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	1		1		36
GEORGIA POWER CO | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	0		0		0
GEORGIA POWER CO | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(5)		(5)		0
GEORGIA POWER CO | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	6		6		29
GEORGIA POWER CO | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					7
GEORGIA POWER CO | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	0	0
GEORGIA POWER CO | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)	(1)	(3)	(2)
GULF POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)			(2)	(7)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			0	0
GULF POWER CO | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(28)		(28)		(24)
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)			(1)	0
GULF POWER CO | Energy-related derivatives | Depreciation and amortization
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			0	0
GULF POWER CO | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(15)		(15)		(9)
GULF POWER CO | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(13)		(13)		(16)
GULF POWER CO | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	0		0		1
GULF POWER CO | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					0
GULF POWER CO | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(1)	(2)	(1)	(7)
GULF POWER CO | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	0	0
MISSISSIPPI POWER CO | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(8)		(8)		(7)
MISSISSIPPI POWER CO | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(5)		(5)		(5)
MISSISSIPPI POWER CO | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(3)		(3)		(3)
MISSISSIPPI POWER CO | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	0		0		1
MISSISSIPPI POWER CO | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					0
MISSISSIPPI POWER CO | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)			0	0
MISSISSIPPI POWER CO | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			(1)	(1)
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Collateral already posted, aggregate fair value	71		71		62
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(2)		(4)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0		0
SOUTHERN Co GAS | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	3		3		17
Collateral already posted, aggregate fair value	1		1		8
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(2)		(4)
SOUTHERN Co GAS | Energy-related derivatives | Cost of natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0		0
SOUTHERN Co GAS | Energy-related derivatives | Other regulatory assets, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	(1)		(1)		(1)
SOUTHERN Co GAS | Energy-related derivatives | Other regulatory assets, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	0		0		0
SOUTHERN Co GAS | Energy-related derivatives | Other regulatory liabilities, current
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet	4		4		17
SOUTHERN Co GAS | Energy-related derivatives | Other regulatory liabilities, deferred
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory hedge unrealized gain (loss) recognized on the balance sheet					$ 1
SOUTHERN Co GAS | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0		0
SOUTHERN Co GAS | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0		0
SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	64	(39)	52	(39)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	72	(21)	78	(22)
SOUTHERN POWER CO | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(7)	0	(15)	0
SOUTHERN POWER CO | Energy-related derivatives | Depreciation and amortization
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(2)	0	(6)	0
SOUTHERN POWER CO | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)			0	0
SOUTHERN POWER CO | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			0	(1)
SOUTHERN POWER CO | Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	71	(39)	67	(39)
SOUTHERN POWER CO | Foreign Exchange Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(5)	(1)	(12)	(1)
SOUTHERN POWER CO | Foreign Exchange Contract | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 79	(20)	$ 96	(20)
Predecessor | SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)		(19)		(64)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)		(2)		(1)
Predecessor | SOUTHERN Co GAS | Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)		0		0
Predecessor | SOUTHERN Co GAS | Energy-related derivatives | Cost of natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)		(1)		(1)
Predecessor | SOUTHERN Co GAS | Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)		(19)		(64)
Predecessor | SOUTHERN Co GAS | Interest Rate Contract | Interest expense, net of amounts capitalized
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)		$ (1)		$ 0

Derivatives - Pre-tax Effects59

Derivatives - Pre-tax Effects of Derivatives Not Designated as Hedging (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Energy-related derivatives | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 14	$ 0	$ 61	$ 0
Energy-related derivatives | Natural gas revenues | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	16	0	65	0
Energy-related derivatives | Cost of natural gas | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(2)	0	(4)	0
Southern Company | Weather Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	1		15
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net			49
SOUTHERN Co GAS | Energy-related derivatives | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	14		61
SOUTHERN Co GAS | Energy-related derivatives | Natural gas revenues | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	16		65
SOUTHERN Co GAS | Energy-related derivatives | Cost of natural gas | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ (2)		(4)
SOUTHERN Co GAS | Weather Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net			$ 15
SOUTHERN Co GAS | Predecessor
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net				(162)
SOUTHERN Co GAS | Predecessor | Energy-related derivatives | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		(82)		(63)
SOUTHERN Co GAS | Predecessor | Energy-related derivatives | Natural gas revenues | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		(21)		(1)
SOUTHERN Co GAS | Predecessor | Energy-related derivatives | Cost of natural gas | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		$ (61)		$ (62)

Derivatives - Pre-tax Effects60

Derivatives - Pre-tax Effects of Derivatives as Fair Value Hedging Relationships (Details) - Interest Rate Contract - Interest expense, net of amounts capitalized - Fair Value Hedging [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Southern Company
Derivative Instruments, Gain (Loss) [Line Items]
Derivative assets, fair value, gross asset	$ 7	$ 4	$ (1)	$ 24
GEORGIA POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Derivative assets, fair value, gross asset	$ 0	$ 0	$ (1)	$ 15

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) $ / shares in Units, $ in Millions	Jul. 01, 2016USD ($)	May 09, 2016USD ($)$ / shares	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2020	Aug. 01, 2017MW	Dec. 31, 2016USD ($)MW
Business Acquisition [Line Items]
Goodwill			$ 6,271		$ 6,271				$ 6,251
Revenues			5,430	$ 4,459	11,202	$ 8,451
Consolidated net income (loss) attributable to Southern Company			(1,381)	623	(723)	1,112
Construction work in progress			7,440		7,440				8,977
SOUTHERN Co GAS
Business Acquisition [Line Items]
Goodwill			5,967		5,967				5,967
Revenues			716		2,276
Consolidated net income (loss) attributable to Southern Company			49		288
Construction work in progress			779		779				496
SOUTHERN POWER CO
Business Acquisition [Line Items]
Goodwill			2		2				2
Revenues			529	373	979	688
Consolidated net income (loss) attributable to Southern Company			82	$ 89	151	$ 139
Total costs of construction					421
Construction work in progress			344		344				$ 398
SOUTHERN Co GAS
Business Acquisition [Line Items]
Aggregate purchase price	$ 8,000
Goodwill			5,967		$ 5,967
SOUTHERN Co GAS | Minimum
Business Acquisition [Line Items]
Estimated lives of intangible assets					1 year
SOUTHERN Co GAS | Maximum
Business Acquisition [Line Items]
Estimated lives of intangible assets					28 years
PowerSecure International, Inc.
Business Acquisition [Line Items]
Aggregate purchase price		$ 429
Goodwill			284		$ 284
Acquisition, share price (in dollars per share) | $ / shares		$ 18.75
PowerSecure International, Inc. | Minimum
Business Acquisition [Line Items]
Estimated lives of intangible assets					1 year
PowerSecure International, Inc. | Maximum
Business Acquisition [Line Items]
Estimated lives of intangible assets					26 years
Series of Construction Projects | SOUTHERN POWER CO
Business Acquisition [Line Items]
Construction work in progress			49		$ 49
Series of Construction Projects | Minimum | SOUTHERN POWER CO
Business Acquisition [Line Items]
Estimated future construction payments			170		170
Series of Construction Projects | Maximum | SOUTHERN POWER CO
Business Acquisition [Line Items]
Estimated future construction payments			$ 190		$ 190
Renewable Energy Systems Americas, Inc. | SOUTHERN POWER CO
Business Acquisition [Line Items]
Approx. nameplate capacity, wind (MW) | MW									3,000
Wind Generating Facility | Scenario, Forecast | SOUTHERN POWER CO
Business Acquisition [Line Items]
Project qualification for production tax credits, percentage							100.00%
Production tax credits, project qualification period							10 years
Subsequent Event | SOUTHERN POWER CO
Business Acquisition [Line Items]
Ownership percentage by parent								100.00%
Approximate Nameplate Capacity (MW) | MW								148

Acquisitions - Schedule of Acqu

Acquisitions - Schedule of Acquisitions (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 6,271	$ 6,251
SOUTHERN Co GAS
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Current assets	1,557
Property, plant, and equipment	10,108
Goodwill	5,967
Intangible assets	400
Regulatory assets	1,118
Other assets	229
Current liabilities	(2,201)
Other liabilities	(4,742)
Long-term debt	(4,261)
Noncontrolling interest	(174)
Total purchase price	8,001
PowerSecure International, Inc.
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Current assets	172
Property, plant, and equipment	46
Goodwill	284
Intangible assets	106
Other assets	4
Current liabilities	(121)
Long-term debt, including current portion	(48)
Other liabilities	(14)
Total purchase price	429
SOUTHERN POWER CO
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 2	$ 2

Acquisitions - Schedule of Pro

Acquisitions - Schedule of Pro Forma Consolidated Information (Details) - SOUTHERN Co GAS $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016USD ($)$ / shares
Business Acquisition [Line Items]
Operating revenues | $	$ 10,346
Net income attributable to Southern Company | $	$ 1,255
Basic EPS (in dollars per share) | $ / shares	$ 1.34
Diluted EPS (in dollars per share) | $ / shares	$ 1.33

Acquisitions - Schedule of Cons

Acquisitions - Schedule of Construction Projects (Details) - SOUTHERN POWER CO - MW	Jan. 06, 2017	Apr. 30, 2017	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2017
Bethel
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)	276
Southern Power Percentage Ownership	100.00%
PPA Contract Period	12 years
East Pecos
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)					120
PPA Contract Period			15 years
Lamesa
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)					102
PPA Contract Period		15 years
Scenario, Forecast | Mankato
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)				345
PPA Contract Period				20 years

Joint Ownership Agreements - Ba

Joint Ownership Agreements - Balance Sheet Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	$ 1,632	$ 1,549
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	1,610	1,541
SNG | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	1,405	1,394
Triton | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	43	44
Atlantic Coast Pipeline | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	31	30
PennEast Pipeline | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	45	22
Triton | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	53	33
Pivotal JAX LNG, LLC | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	32	16
Other | SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	$ 1	$ 2

Joint Ownership Agreements - In

Joint Ownership Agreements - Income Statement Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	$ 28	$ (1)	$ 67	$ (1)
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	29		68
SOUTHERN Co GAS | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		1		2
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	24		58
SOUTHERN Co GAS | SNG | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		0		0
SOUTHERN Co GAS | Triton
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	2		2
SOUTHERN Co GAS | Triton | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		1		1
SOUTHERN Co GAS | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	0		1
SOUTHERN Co GAS | Atlantic Coast Pipeline | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		0		1
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	1		4
SOUTHERN Co GAS | PennEast Pipeline | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		0		0
SOUTHERN Co GAS | Triton
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments	$ 2		$ 3
SOUTHERN Co GAS | Triton | Predecessor
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investments		$ 0		$ 0

Joint Ownership Agreements - Na

Joint Ownership Agreements - Narrative (Details) - SNG - SOUTHERN Co GAS - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		50.00%
Capital contributions from parent company	$ 50

Joint Ownership Agreements - 68

Joint Ownership Agreements - Investment in SNG (Details) - SNG - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Schedule of Equity Method Investments [Line Items]
Revenues	$ 143	$ 298
Operating income	63	147
Net income	$ 48	$ 114

Segment and Related Informati69

Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)statesegment	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)statesegment	Jun. 30, 2016USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates | state	4		4
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of natural gas distribution utilities	7		7
Number of reportable segments			4
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Wholesale revenues, affiliates | $	$ 90	$ 107	$ 190	$ 204

Segment and Related Informati70

Segment and Related Information - Financial Data for Business Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating revenues	$ 5,430	$ 4,459	$ 11,202	$ 8,451
Segment net income	(1,381)	623	(723)	1,112
Total assets	108,684		108,684		$ 109,697
Kemper IGCC
Segment Reporting Information [Line Items]
Pre-tax charge to income	3,000	81	3,100	134
After tax charge to income	2,100	50	2,200	83
Plant Scherer Unit 3
Segment Reporting Information [Line Items]
After tax charge to income			20
Loss on Plant Scherer Unit 3			33
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,585	4,379	8,716	8,360
Segment net income	(1,360)	688	(859)	1,203
Total assets	85,889		85,889		86,994
Intersegment Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(101)	(109)	(206)	(212)
Segment net income	0	0	0	0
Total assets	(317)		(317)		(316)
Consolidation Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(37)	(45)	(79)	(81)
Segment net income	(2)	(4)	0	(7)
Total assets	(1,362)		(1,362)		(1,624)
Traditional Electric Operating Companies | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,157	4,115	7,943	7,884
Segment net income	(1,442)	599	(1,010)	1,064
Total assets	71,503		71,503		72,141
SOUTHERN POWER CO | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	529	373	979	688
Segment net income	82	89	151	139
Total assets	14,703		14,703		15,169
SOUTHERN Co GAS | Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	716		2,276
Segment net income	49		288
Total assets	21,809		21,809		21,853
All Other
Segment Reporting Information [Line Items]
Operating revenues	166	125	289	172
Segment net income	(68)	(61)	(152)	(84)
Total assets	2,348		2,348		2,474
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	529	373	979	688
Segment net income	82	89	151	139
Total assets	14,703		14,703		15,169
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	716		2,276
Segment net income	49		288
Total assets	21,809		21,809		21,853
SOUTHERN Co GAS | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	769		2,393
Segment net income	50		282
Total assets	23,720		23,720		24,875
SOUTHERN Co GAS | Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(56)		(122)
Segment net income	0		0
Total assets	(13,093)		(13,093)		(14,167)
SOUTHERN Co GAS | Gas distribution operations | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	603		1,783
Segment net income	54		171
Total assets	18,257		18,257		19,453
SOUTHERN Co GAS | Gas marketing services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	166		454
Segment net income	4		35
Total assets	2,093		2,093		2,084
SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	(12)		119
Segment net income	(17)		51
Total assets	989		989		1,127
Less Gross Gas Costs	1,666		3,510
SOUTHERN Co GAS | Gas Midstream Operations | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	12		37
Segment net income	9		25
Total assets	2,381		2,381		2,211
SOUTHERN Co GAS | All Other | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	3		5
Segment net income	(1)		6
Total assets	11,182		11,182		$ 11,145
Predecessor | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		571		1,905
EBIT		(24)		328
Segment net income		(51)		131
Predecessor | SOUTHERN Co GAS | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		611		2,003
EBIT		30		388
Predecessor | SOUTHERN Co GAS | Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues		(42)		(102)
EBIT		1		0
Predecessor | SOUTHERN Co GAS | Gas distribution operations | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		547		1,575
EBIT		118		353
Predecessor | SOUTHERN Co GAS | Gas marketing services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		149		435
EBIT		29		109
Predecessor | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		(95)		(32)
EBIT		(112)		(68)
Less Gross Gas Costs		1,214		2,675
Predecessor | SOUTHERN Co GAS | Gas Midstream Operations | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		10		25
EBIT		(5)		(6)
Predecessor | SOUTHERN Co GAS | All Other | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		2		4
EBIT		(55)		(60)
Third Party Gross Revenues | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	1,531		3,370
Third Party Gross Revenues | Predecessor | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		1,061		2,500
Intercompany Revenues | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	123		259
Intercompany Revenues | Predecessor | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		58		143
Total Gross Revenues | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	$ 1,654		$ 3,629
Total Gross Revenues | Predecessor | SOUTHERN Co GAS | Wholesale Gas Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues		$ 1,119		$ 2,643

Segment and Related Informati71

Segment and Related Information - Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue from External Customer [Line Items]
Electric Utilities' Revenues	$ 4,585	$ 4,379	$ 8,716	$ 8,360
Gas Revenue	716		2,276
Retail
Revenue from External Customer [Line Items]
Electric Utilities' Revenues	3,777	3,748	7,171	7,124
Wholesale
Revenue from External Customer [Line Items]
Electric Utilities' Revenues	618	446	1,149	842
Other
Revenue from External Customer [Line Items]
Electric Utilities' Revenues	190	$ 185	396	$ 394
Gas distribution operations
Revenue from External Customer [Line Items]
Gas Revenue	557		1,689
Gas marketing services
Revenue from External Customer [Line Items]
Gas Revenue	166		454
Other
Revenue from External Customer [Line Items]
Gas Revenue	$ (7)		$ 133