Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 1,975	$ 1,404
Receivables --
Customer accounts receivable	1,565	1,058
Energy marketing receivable	623	0
Unbilled revenues	706	397
Under recovered regulatory clause revenues	18	63
Income taxes receivable, current	544	144
Other accounts and notes receivable	377	398
Accumulated provision for uncollectible accounts	(43)	(13)
Materials and supplies	1,462	1,061
Fossil fuel for generation	689	868
Natural gas for sale	631	0
Prepaid expenses	364	495
Other regulatory assets, current	581	580
Other current assets	230	71
Total current assets	9,722	6,526
Property, Plant, and Equipment:
In service	98,416	75,118
Less accumulated depreciation	29,852	24,253
Plant in service, net of depreciation	68,564	50,865
Other utility plant, net	0	233
Nuclear fuel, at amortized cost	905	934
Construction work in progress	8,977	9,082
Total property, plant, and equipment	78,446	61,114
Other Property and Investments:
Goodwill	6,251	2
Equity investments in unconsolidated subsidiaries	1,549	6
Other intangible assets, net of amortization	970	317
Nuclear decommissioning trusts, at fair value	1,606	1,512
Leveraged leases	774	755
Miscellaneous property and investments	270	160
Total other property and investments	11,420	2,752
Deferred Charges and Other Assets:
Deferred charges related to income taxes	1,629	1,560
Unamortized loss on reacquired debt	223	227
Other regulatory assets, deferred	6,851	4,989
Income taxes receivable, non-current	11	413
Accumulated deferred income taxes – assets	52	56
Other deferred charges and assets	1,395	737
Total deferred charges and other assets	10,109	7,926
Total Assets	109,697	78,318
Current Liabilities:
Securities due within one year, Other	2,587	2,674
Notes payable	2,241	1,376
Energy marketing trade payables	597	0
Accounts payable	2,228	1,905
Customer deposits	558	404
Accrued taxes --
Accrued income taxes	193	9
Unrecognized tax benefits	385	10
Other accrued taxes	667	484
Accrued interest	518	249
Accrued compensation	915	777
Asset retirement obligations, current	378	217
Liabilities from risk management activities, net of collateral	107	156
Acquisitions Payable	489	0
Other regulatory liabilities, current	236	278
Over recovered regulatory clause revenues, current	135	106
Other current liabilities	683	484
Total current liabilities	12,917	9,129
Long-Term Debt
Unamortized debt issuance expense	(213)	(241)
Long-term Debt	42,629	24,688
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	14,092	12,322
Deferred credits related to income taxes	219	187
Accumulated deferred investment tax credits	2,228	1,219
Employee benefit obligations	2,299	2,582
Asset retirement obligations, deferred	4,136	3,542
Unrecognized tax benefits, deferred	0	370
Accrued environmental remediation	397	42
Other cost of removal obligations	2,748	1,162
Other regulatory liabilities, deferred	258	254
Other deferred credits and liabilities	880	678
Total deferred credits and other liabilities	27,257	22,358
Total Liabilities	82,803	56,175
Redeemable Preferred Stock of Subsidiaries	118	118
Redeemable Noncontrolling Interests	164	43
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	4,952	4,572
Paid-in capital	9,661	6,282
Retained earnings	10,356	10,010
Accumulated other comprehensive loss	(180)	(130)
Common Stockholders' Equity	24,758	20,592
Noncontrolling interests	1,854	1,390
Total stockholders' equity	26,612	21,982
Total Liabilities and Stockholders' Equity	109,697	78,318
Alabama Power [Member]
Current Assets:
Cash and cash equivalents	420	194
Receivables --
Customer accounts receivable	348	375
Unbilled revenues	146	119
Income taxes receivable, current	0	142
Other accounts and notes receivable	27	20
Affiliated	40	50
Accumulated provision for uncollectible accounts	(10)	(10)
Materials and supplies	435	398
Fossil fuel for generation	205	239
Prepaid expenses	34	83
Other regulatory assets, current	149	182
Other current assets	11	9
Total current assets	1,805	1,801
Property, Plant, and Equipment:
In service	26,031	24,750
Less accumulated depreciation	9,112	8,736
Plant in service, net of depreciation	16,919	16,014
Nuclear fuel, at amortized cost	336	363
Construction work in progress	491	801
Total property, plant, and equipment	17,746	17,178
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	66	71
Nuclear decommissioning trusts, at fair value	792	737
Miscellaneous property and investments	112	96
Total other property and investments	970	904
Deferred Charges and Other Assets:
Deferred charges related to income taxes	525	522
Deferred under recovered regulatory clause revenues	150	99
Other regulatory assets, deferred	1,157	1,114
Other deferred charges and assets	163	103
Total deferred charges and other assets	1,995	1,838
Total Assets	22,516	21,721
Current Liabilities:
Securities due within one year, Other	561	200
Notes payable	0	0
Accounts payable - Affiliated	297	278
Accounts payable - Other	433	410
Customer deposits	88	88
Accrued taxes --
Accrued income taxes	45	0
Other accrued taxes	42	38
Accrued interest	78	73
Accrued compensation	193	175
Other regulatory liabilities, current	85	240
Other current liabilities	76	93
Total current liabilities	1,898	1,595
Long-Term Debt
Unamortized debt premium (discount), net	(9)	(9)
Unamortized debt issuance expense	(46)	(45)
Long-term Debt	6,535	6,654
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	4,654	4,241
Deferred credits related to income taxes	65	70
Accumulated deferred investment tax credits	110	118
Employee benefit obligations	300	388
Asset retirement obligations, deferred	1,503	1,448
Other cost of removal obligations	684	722
Other regulatory liabilities, deferred	100	136
Other deferred credits and liabilities	63	76
Total deferred credits and other liabilities	7,479	7,199
Total Liabilities	15,912	15,448
Redeemable Preferred Stock of Subsidiaries	85	85
Redeemable Preferred Stock	85	85
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	1,222	1,222
Paid-in capital	2,613	2,341
Retained earnings	2,518	2,461
Accumulated other comprehensive loss	(30)	(32)
Common Stockholders' Equity	6,323	5,992
Preference Stock	196	196
Total stockholders' equity	6,323	5,992
Total Liabilities and Stockholders' Equity	22,516	21,721
Georgia Power [Member]
Current Assets:
Cash and cash equivalents	3	67
Receivables --
Customer accounts receivable	523	541
Unbilled revenues	224	188
Joint owner accounts receivable	57	227
Income taxes receivable, current	0	114
Other accounts and notes receivable	81	57
Affiliated	18	18
Accumulated provision for uncollectible accounts	(3)	(2)
Materials and supplies	479	449
Fossil fuel for generation	298	402
Prepaid expenses	105	230
Other regulatory assets, current	193	213
Other current assets	38	19
Total current assets	2,016	2,523
Property, Plant, and Equipment:
In service	33,841	31,841
Less accumulated depreciation	11,317	10,903
Plant in service, net of depreciation	22,524	20,938
Other utility plant, net	0	171
Nuclear fuel, at amortized cost	569	572
Construction work in progress	4,939	4,775
Total property, plant, and equipment	28,032	26,456
Other Property and Investments:
Equity investments in unconsolidated subsidiaries	60	64
Nuclear decommissioning trusts, at fair value	814	775
Miscellaneous property and investments	46	43
Total other property and investments	920	882
Deferred Charges and Other Assets:
Deferred charges related to income taxes	676	679
Other regulatory assets, deferred	2,774	2,152
Other deferred charges and assets	417	173
Total deferred charges and other assets	3,867	3,004
Total Assets	34,835	32,865
Current Liabilities:
Securities due within one year, Other	460	712
Notes payable	391	158
Accounts payable - Affiliated	438	411
Accounts payable - Other	589	750
Customer deposits	265	264
Accrued taxes --
Accrued income taxes	17	12
Other accrued taxes	390	325
Accrued interest	106	99
Accrued compensation	224	205
Asset retirement obligations, current	299	179
Other regulatory liabilities, current	31	16
Over recovered regulatory clause revenues, current	84	10
Other current liabilities	182	154
Total current liabilities	3,476	3,295
Long-Term Debt
Unamortized debt premium (discount), net	(10)	(10)
Unamortized debt issuance expense	(117)	(118)
Long-term Debt	10,225	9,616
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	6,000	5,627
Deferred credits related to income taxes	121	105
Accumulated deferred investment tax credits	256	204
Employee benefit obligations	703	949
Deferred capacity expense	217	203
Asset retirement obligations, deferred	2,233	1,737
Other deferred credits and liabilities	199	347
Total deferred credits and other liabilities	9,512	8,969
Total Liabilities	23,213	21,880
Redeemable Preferred Stock	45	45
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	398	398
Paid-in capital	6,885	6,275
Retained earnings	4,086	4,061
Accumulated other comprehensive loss	(13)	(15)
Common Stockholders' Equity	11,356	10,719
Preference Stock	221	221
Total stockholders' equity	11,356	10,719
Total Liabilities and Stockholders' Equity	34,835	32,865
Gulf Power [Member]
Current Assets:
Cash and cash equivalents	56	74
Receivables --
Customer accounts receivable	72	76
Unbilled revenues	55	54
Under recovered regulatory clause revenues	17	20
Income taxes receivable, current	0	27
Other accounts and notes receivable	6	9
Affiliated	17	1
Accumulated provision for uncollectible accounts	(1)	(1)
Materials and supplies	55	56
Fossil fuel for generation	71	108
Prepaid expenses	18	8
Other regulatory assets, current	44	90
Other current assets	12	14
Total current assets	422	536
Property, Plant, and Equipment:
In service	5,140	5,045
Less accumulated depreciation	1,382	1,296
Plant in service, net of depreciation	3,758	3,749
Other utility plant, net	0	62
Construction work in progress	51	48
Total property, plant, and equipment	3,809	3,859
Deferred Charges and Other Assets:
Deferred charges related to income taxes	58	61
Other regulatory assets, deferred	512	427
Other deferred charges and assets	21	37
Total deferred charges and other assets	591	525
Total Assets	4,822	4,920
Current Liabilities:
Securities due within one year, Other	87	110
Notes payable	268	142
Accounts payable - Affiliated	59	55
Accounts payable - Other	54	44
Customer deposits	35	36
Accrued taxes --
Accrued income taxes	1	4
Other accrued taxes	19	9
Accrued interest	8	9
Accrued compensation	40	36
Liabilities from risk management activities, net of collateral	9	49
Deferred capacity expense, current	22	22
Other regulatory liabilities, current	16	22
Other current liabilities	31	29
Total current liabilities	649	567
Long-Term Debt
Unamortized debt premium (discount), net	(5)	(8)
Unamortized debt issuance expense	(7)	(8)
Long-term Debt	987	1,193
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	948	893
Employee benefit obligations	96	129
Deferred capacity expense	119	141
Asset retirement obligations, deferred	120	113
Other cost of removal obligations	249	233
Other regulatory liabilities, deferred	47	47
Other deferred credits and liabilities	71	102
Total deferred credits and other liabilities	1,650	1,658
Total Liabilities	3,286	3,418
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	503	503
Paid-in capital	589	567
Retained earnings	296	285
Accumulated other comprehensive loss	1	0
Common Stockholders' Equity	1,389	1,355
Preference Stock	147	147
Total stockholders' equity	1,389	1,355
Total Liabilities and Stockholders' Equity	4,822	4,920
Mississippi Power [Member]
Current Assets:
Cash and cash equivalents	224	98
Receivables --
Customer accounts receivable	29	26
Unbilled revenues	42	36
Income taxes receivable, current	544	20
Other accounts and notes receivable	14	10
Affiliated	15	20
Materials and supplies	76	75
Fossil fuel for generation	100	104
Other regulatory assets, current	115	95
Prepaid income taxes	0	39
Other current assets	8	8
Total current assets	1,167	531
Property, Plant, and Equipment:
In service	4,865	4,886
Less accumulated depreciation	1,289	1,262
Plant in service, net of depreciation	3,576	3,624
Construction work in progress	2,545	2,254
Total property, plant, and equipment	6,121	5,878
Other Property and Investments:
Total other property and investments	12	11
Deferred Charges and Other Assets:
Deferred charges related to income taxes	361	290
Other regulatory assets, deferred	518	525
Income taxes receivable, non-current	0	544
Other deferred charges and assets	56	61
Total deferred charges and other assets	935	1,420
Total Assets	8,235	7,840
Current Liabilities:
Securities due within one year, Parent	551	0
Securities due within one year, Other	629	728
Notes payable	23	500
Accounts payable - Affiliated	62	85
Accounts payable - Other	135	135
Customer deposits	16	16
Accrued taxes --
Accrued income taxes	99	85
Unrecognized tax benefits	383	0
Accrued interest	46	18
Accrued compensation	42	37
Asset retirement obligations, current	32	22
Over recovered regulatory clause liabilities	51	96
Customer liability associated with Kemper refunds	1	73
Other current liabilities	19	41
Total current liabilities	1,538	1,836
Long-Term Debt
Long-term debt affiliated	551	0
Unamortized debt issuance expense	(8)	(8)
Long-term Debt	2,424	1,886
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	756	762
Employee benefit obligations	115	153
Asset retirement obligations, deferred	146	154
Unrecognized tax benefits, deferred	0	368
Other cost of removal obligations	170	165
Other regulatory liabilities, deferred	84	79
Other deferred credits and liabilities	26	45
Total deferred credits and other liabilities	1,297	1,726
Total Liabilities	5,259	5,448
Redeemable Preferred Stock	33	33
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	38	38
Paid-in capital	3,525	2,893
Retained earnings	(616)	(566)
Accumulated other comprehensive loss	(4)	(6)
Common Stockholders' Equity	2,943	2,359
Total stockholders' equity	2,943	2,359
Total Liabilities and Stockholders' Equity	8,235	7,840
Southern Power [Member]
Current Assets:
Cash and cash equivalents	1,099	830
Receivables --
Customer accounts receivable	102	75
Other accounts and notes receivable	34	19
Affiliated	57	30
Materials and supplies	337	63
Fossil fuel for generation	15	16
Prepaid income taxes	74	45
Other current assets	39	30
Total current assets	1,757	1,108
Property, Plant, and Equipment:
In service	12,728	7,275
Less accumulated depreciation	1,484	1,248
Plant in service, net of depreciation	11,244	6,027
Construction work in progress	398	1,137
Total property, plant, and equipment	11,642	7,164
Other Property and Investments:
Other intangible assets, net of amortization		317
Intangible assets, net of amortization	436	319
Total other property and investments	436	319
Deferred Charges and Other Assets:
Prepaid long-term service agreements	101	166
Accumulated deferred income taxes – assets	594	0
Other deferred charges and assets -- affiliated	13	9
Other deferred charges and assets	626	139
Total deferred charges and other assets	1,334	314
Total Assets	15,169	8,905
Current Liabilities:
Securities due within one year, Other	560	403
Notes payable	209	137
Accounts payable - Affiliated	88	66
Accounts payable - Other	278	327
Accrued taxes --
Accrued income taxes	148	198
Other accrued taxes	7	5
Accrued interest	36	23
Acquisitions Payable	461	0
Contingent consideration	46	36
Other current liabilities	70	44
Total current liabilities	1,903	1,239
Long-Term Debt
Unamortized debt premium (discount), net	(12)	0
Unamortized debt issuance expense	(29)	(19)
Long-term Debt	5,068	2,719
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	152	601
Accumulated deferred investment tax credits	1,839	889
Accrued income taxes, non-current	0	109
Asset retirement obligations, deferred	64	21
Deferred capacity revenues -- affiliated	17	17
Other deferred credits and liabilities	287	3
Total deferred credits and other liabilities	2,359	1,640
Total Liabilities	9,330	5,598
Redeemable Noncontrolling Interest	164	43
Commitments and Contingent Matters
Common Stockholders' Equity:
Common stock	0	0
Paid-in capital	3,671	1,822
Retained earnings	724	657
Accumulated other comprehensive loss	35	4
Common Stockholders' Equity	4,430	2,483
Noncontrolling interests	1,245	781
Total stockholders' equity	5,675	3,264
Total Liabilities and Stockholders' Equity	15,169	8,905
Southern Power [Member] | 1.85% due 2017 [Member]
Long-Term Debt
Senior notes	0	500
Southern Power [Member] | 1.50% due 2018 [Member]
Long-Term Debt
Senior notes	350	350
Southern Power [Member] | Senior Notes Due Two Thousand Nineteen [Member]
Long-Term Debt
Senior notes	600	0
Southern Power [Member] | 2.375% due 2020 [Member]
Long-Term Debt
Senior notes	300	300
Southern Power [Member] | Senior Notes Due Two Thousand Twenty One [Member]
Long-Term Debt
Senior notes	300	0
Southern Power [Member] | Senior Notes Due Two Thousand Twenty Two Through Two Thousand Forty Six [Member]
Long-Term Debt
Senior notes	3,224	1,575
Southern Power [Member] | 1.88% due 2018 [Member]
Long-Term Debt
Other long-term debt	320	0
Southern Power [Member] | Other Long Term Notes Due Two Thousand Thirty Two to Two Thousand Thirty Six [Member]
Long-Term Debt
Other long-term debt	15	13
Successor [Member] | Southern Company Gas [Member]
Current Assets:
Cash and cash equivalents	19
Receivables --
Customer accounts receivable	364
Energy marketing receivable	623
Unbilled revenues	239
Other accounts and notes receivable	76
Accumulated provision for uncollectible accounts	(27)
Materials and supplies	26
Natural gas for sale	631
Prepaid expenses	55
Other regulatory assets, current	81
Prepaid income taxes	24
Assets from risk management activities, net of collateral	128
Other current assets	11
Total current assets	2,250
Property, Plant, and Equipment:
In service	14,508
Less accumulated depreciation	4,439
Plant in service, net of depreciation	10,069
Construction work in progress	496
Total property, plant, and equipment	10,565
Other Property and Investments:
Goodwill	5,967
Equity investments in unconsolidated subsidiaries	1,541
Other intangible assets, net of amortization	366
Miscellaneous property and investments	21
Total other property and investments	7,895
Deferred Charges and Other Assets:
Other regulatory assets, deferred	973
Other deferred charges and assets	170
Total deferred charges and other assets	1,143
Total Assets	21,853
Current Liabilities:
Securities due within one year, Other	22
Notes payable	1,257
Energy marketing trade payables	597
Accounts payable	348
Customer deposits	153
Accrued taxes --
Accrued income taxes	26
Other accrued taxes	68
Accrued interest	48
Accrued compensation	58
Liabilities from risk management activities, net of collateral	62
Other regulatory liabilities, current	102
Accrued environmental remediation, current	69
Other current liabilities	108
Total current liabilities	2,918
Long-Term Debt
Unamortized debt premium (discount), net	(9)
Long-term Debt	5,259
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	1,975
Employee benefit obligations	441
Accrued environmental remediation	357
Other cost of removal obligations	1,616
Other regulatory liabilities, deferred	51
Other deferred credits and liabilities	127
Total deferred credits and other liabilities	4,567
Total Liabilities	12,744
Redeemable Noncontrolling Interests	0
Commitments and Contingent Matters
Common Stockholders' Equity:
Paid-in capital	9,095
Retained earnings	(12)
Accumulated other comprehensive loss	26
Common Stockholders' Equity	9,109
Total stockholders' equity	9,109
Total Liabilities and Stockholders' Equity	21,853
Predecessor [Member] | Southern Company Gas [Member]
Current Assets:
Cash and cash equivalents		19
Receivables --
Customer accounts receivable		316
Energy marketing receivable		445
Unbilled revenues		140
Other accounts and notes receivable		68
Accumulated provision for uncollectible accounts		(29)
Materials and supplies		29
Natural gas for sale		622
Prepaid expenses		67
Other regulatory assets, current		68
Prepaid income taxes		151
Assets from risk management activities, net of collateral		206
Other current assets		13
Total current assets		2,115
Property, Plant, and Equipment:
In service		12,152
Less accumulated depreciation		2,775
Plant in service, net of depreciation		9,377
Construction work in progress		414
Total property, plant, and equipment		9,791
Other Property and Investments:
Goodwill		1,813
Equity investments in unconsolidated subsidiaries		80
Other intangible assets, net of amortization		109
Miscellaneous property and investments		23
Total other property and investments		2,025
Deferred Charges and Other Assets:
Other regulatory assets, deferred		670
Other deferred charges and assets		153
Total deferred charges and other assets		823
Total Assets		14,754
Current Liabilities:
Securities due within one year, Other		545
Notes payable		1,010
Energy marketing trade payables		418
Accounts payable		255
Customer deposits		165
Accrued taxes --
Accrued income taxes		13
Other accrued taxes		46
Accrued interest		49
Accrued compensation		92
Liabilities from risk management activities, net of collateral		44
Other regulatory liabilities, current		134
Accrued environmental remediation, current		67
Other current liabilities		162
Total current liabilities		3,000
Long-Term Debt
Unamortized debt premium (discount), net		(4)
Long-term Debt		3,275
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes		1,912
Employee benefit obligations		515
Accrued environmental remediation		364
Other cost of removal obligations		1,538
Other regulatory liabilities, deferred		53
Other deferred credits and liabilities		122
Total deferred credits and other liabilities		4,504
Total Liabilities		10,779
Redeemable Noncontrolling Interests		0
Commitments and Contingent Matters
Common Stockholders' Equity:
Paid-in capital		2,702
Retained earnings		1,421
Accumulated other comprehensive loss		(186)
Common Stockholders' Equity		3,929
Total stockholders' equity		3,975
Total Liabilities and Stockholders' Equity		14,754
Long-Term Debt, Other [Member] | Mississippi Power [Member]
Current Liabilities:
Securities due within one year, Other	$ 78	$ 728