Consolidated Statements of Capitalization - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Long-Term Debt:
Long-term debt payable to affiliated trusts — variable rate (5.50% at 12/31/18) due 2042	$ 206	$ 206
Maturity
2019	3,156
2020	4,041
2021	3,186
2022	1,974
2023	2,388
Total long-term senior notes and debt	34,025	36,820
Pollution control revenue bonds —
Pollution control revenue bonds	2,585	3,297
Total other long-term debt	10,684	10,987
Unamortized fair value adjustment of long-term debt	474	525
Capitalized lease obligations	197	204
Unamortized debt premium	36	44
Unamortized debt discount	(194)	(206)
Unamortized debt issuance expense	(208)	(226)
Total long-term debt	45,220	48,354
Amount due within one year	3,198	3,892
Amount held for sale	1,286	0
Long-term debt excluding amounts due within one year and held for sale	$ 40,736	$ 44,462
Percent capitalization	58.10%	63.20%
Cumulative preferred stock
Redeemable preferred stock	$ 291	$ 324
Total redeemable preferred stock - percent capitalization	0.40%	0.50%
Common Stockholders' Equity:
Common stock	$ 5,164	$ 5,038
Paid-in capital	11,094	10,469
Treasury, at cost	(38)	(36)
Retained earnings	8,706	8,885
Accumulated other comprehensive loss	(203)	(189)
Total common stockholders' equity	$ 24,723	$ 24,167
Total common stockholders' equity - percent capitalization	35.30%	34.40%
Total preferred and preference stock of subsidiaries - percent capitalization	6.20%	1.90%
Total Stockholders' Equity	$ 29,039	$ 25,528
Total Capitalization	$ 70,066	$ 70,314
Percent capitalization	100.00%	100.00%
Redeemable Preferred Stock, $100 par or stated value | Cumulative preferred stock
Cumulative preferred stock
Redeemable preferred stock	$ 48	$ 81
Redeemable Preferred Stock, $1 par value | Cumulative preferred stock
Cumulative preferred stock
Redeemable preferred stock	243	243
Noncontrolling interests
Common Stockholders' Equity:
Total preferred and preference stock of subsidiaries and noncontrolling interests	4,316	1,361
Senior Notes
Maturity
2018	0	2,352
2019	2,948	3,074
2020	2,271	2,273
2021	2,638	2,643
2022	1,983	2,016
2023	2,290	2,290
Thereafter	19,895	19,902
Adjustable Rate Loans
Maturity
2018	0	1,420
2020	1,875	825
2021	125	25
Pollution control revenue bonds due 2019
Pollution control revenue bonds —
Pollution control revenue bonds	25	25
Pollution control revenue bonds due 2022
Pollution control revenue bonds —
Pollution control revenue bonds	90	90
Pollution control revenue bonds due 2023
Pollution control revenue bonds —
Pollution control revenue bonds	33	33
Pollution control revenue bonds due 2025 through 2049
Pollution control revenue bonds —
Pollution control revenue bonds	1,112	1,346
Pollution control revenue bonds - variable rates (1.77 to 2.23% at 12/31/18) due 2019
Pollution control revenue bonds —
Pollution control revenue bonds	148	148
Pollution control revenue bonds - variable rates (1.76% to 1.87% at 12/31/18) due 2021
Pollution control revenue bonds —
Pollution control revenue bonds	65	65
Pollution control revenue bonds - variable rates (1.76% at 12/31/18) due 2022
Pollution control revenue bonds —
Pollution control revenue bonds	4	4
Pollution control revenue bonds - variable rates (1.70% to 1.87% at 12/31/18) due 2024 to 2053
Pollution control revenue bonds —
Pollution control revenue bonds	1,417	1,585
Plant Daniel revenue bonds (7.13%) due 2021
Pollution control revenue bonds —
Plant Daniel revenue bonds (7.13%) due 2021	270	270
Gas facility revenue bonds - variable rate (1.71% at 12/31/17) due 2022
Pollution control revenue bonds —
Gas facility revenue bonds	0	47
Gas facility revenue bonds - variable rate (1.71% at 12/31/17) due 2024 to 2033
Pollution control revenue bonds —
Gas facility revenue bonds	0	154
FFB loans — 2.57% to 3.86% due 2020
Pollution control revenue bonds —
FFB loans	44	44
FFB loans — 2.57% to 3.86% due 2021
Pollution control revenue bonds —
FFB loans	44	44
FFB loans — 2.57% to 3.86% due 2022
Pollution control revenue bonds —
FFB loans	44	44
FFB loans — 2.57% to 3.86% due 2023
Pollution control revenue bonds —
FFB loans	44	44
FFB loans — 2.57% to 3.86% due 2024 to 2044
Pollution control revenue bonds —
FFB loans	2,449	2,449
First mortgage bonds — 4.70% due 2019
Pollution control revenue bonds —
First mortgage bonds	50	50
First mortgage bonds - 5.80% due 2023
Pollution control revenue bonds —
First mortgage bonds	50	50
First mortgage bonds — 2.66% to 6.58% due 2026 to 2057
Pollution control revenue bonds —
First mortgage bonds	1,225	925
Alabama Power
Long-Term Debt:
Long-term debt payable to affiliated trusts — variable rate (5.50% at 12/31/18) due 2042	206	206
Maturity
2019	200	200
2020	250	250
2021	310
2022	750	750
2023	300	300
Thereafter	5,175	4,675
Total long-term notes payable	6,920	6,420
Pollution control revenue bonds —
Pollution control revenue bonds	1,060	1,060
Total other long-term debt	1,060	1,060
Capitalized lease obligations	4	4
Unamortized debt premium (discount), net	(12)	(11)
Unamortized debt issuance expense	(54)	(51)
Total long-term debt	8,124	7,628
Amount due within one year	201	0
Long-term debt excluding amounts due within one year and held for sale	$ 7,923	$ 7,628
Percent capitalization	50.40%	51.70%
Cumulative preferred stock
Redeemable preferred stock	$ 291	$ 291
Total redeemable preferred stock - percent capitalization	1.90%	2.00%
Common Stockholders' Equity:
Common stock	$ 1,222	$ 1,222
Paid-in capital	3,508	2,986
Retained earnings	2,775	2,647
Accumulated other comprehensive loss	(28)	(26)
Total common stockholders' equity	$ 7,477	$ 6,829
Total common stockholders' equity - percent capitalization	47.70%	46.30%
Total Stockholders' Equity	$ 7,477	$ 6,829
Total Capitalization	$ 15,691	$ 14,748
Percent capitalization	100.00%	100.00%
Alabama Power | Redeemable Preferred Stock, $100 par or stated value | Cumulative preferred stock
Cumulative preferred stock
Redeemable preferred stock	$ 48	$ 48
Alabama Power | Redeemable Preferred Stock, $1 par value | Cumulative preferred stock
Cumulative preferred stock
Redeemable preferred stock	243	243
Alabama Power | Adjustable Rate Loans
Maturity
2021	25	25
Alabama Power | Long-term senior notes and debt maturing 2021
Maturity
2021	220	220
Alabama Power | Pollution control revenue bonds - variable rates (1.76% to 1.87% at 12/31/18) due 2021
Pollution control revenue bonds —
Pollution control revenue bonds	65	65
Alabama Power | Pollution control revenue bonds due 2034
Pollution control revenue bonds —
Pollution control revenue bonds	207	207
Alabama Power | Pollution control revenue bonds - variable rates (1.70% to 1.80% at 12/31/18) due 2024-2038
Pollution control revenue bonds —
Pollution control revenue bonds	788	788
Georgia Power
Maturity
2018	0	747
2019	621
2020	1,006
2021	375
2022	505
2023	153
Thereafter	3,325	4,075
Total long-term notes payable	5,598	7,196
Pollution control revenue bonds —
Pollution control revenue bonds	1,460	1,821
Total other long-term debt	4,355	4,716
Capitalized lease obligations	142	154
Unamortized debt premium (discount), net	(6)	(12)
Unamortized debt issuance expense	(108)	(124)
Total long-term debt	9,981	11,930
Amount due within one year	617	857
Long-term debt excluding amounts due within one year and held for sale	$ 9,364	$ 11,073
Percent capitalization	39.50%	48.10%
Common Stockholders' Equity:
Common stock	$ 398	$ 398
Paid-in capital	10,322	7,328
Retained earnings	3,612	4,215
Accumulated other comprehensive loss	(9)	(10)
Total common stockholders' equity	$ 14,323	$ 11,931
Total common stockholders' equity - percent capitalization	60.50%	51.90%
Total Stockholders' Equity	$ 14,323	$ 11,931
Total Capitalization	$ 23,687	$ 23,004
Percent capitalization	100.00%	100.00%
Georgia Power | Adjustable Rate Loans
Maturity
2018	$ 0	$ 100
Georgia Power | Long-term senior notes and debt maturing 2020
Maturity
2020	950	950
Georgia Power | Long-term senior notes and debt maturing 2019
Maturity
2019	498	499
Georgia Power | Long-term senior notes and debt maturing 2021
Maturity
2021	325	325
Georgia Power | Long-term senior notes and debt maturing 2022
Maturity
2022	400	400
Georgia Power | Long-term senior notes and debt maturing 2023
Maturity
2023	100	100
Georgia Power | Pollution control revenue bonds due 2022
Pollution control revenue bonds —
Pollution control revenue bonds	53	53
Georgia Power | Pollution control revenue bonds due 2025 through 2049
Pollution control revenue bonds —
Pollution control revenue bonds	748	940
Georgia Power | Pollution control revenue bonds - variable rates (1.77% to 1.78% at 12/31/18) due 2019
Pollution control revenue bonds —
Pollution control revenue bonds	108	108
Georgia Power | Pollution control revenue bonds - variable rates (0.00% to 0.00% at 12/31/18) due 2026-2052
Pollution control revenue bonds —
Pollution control revenue bonds	551	720
Georgia Power | FFB loans — 2.57% to 3.86% due 2020
Pollution control revenue bonds —
FFB loans	44	44
Georgia Power | FFB loans — 2.57% to 3.86% due 2021
Pollution control revenue bonds —
FFB loans	44	44
Georgia Power | FFB loans — 2.57% to 3.86% due 2022
Pollution control revenue bonds —
FFB loans	44	44
Georgia Power | FFB loans — 2.57% to 3.86% due 2023
Pollution control revenue bonds —
FFB loans	44	44
Georgia Power | FFB loans — 2.57% to 3.86% due 2024 to 2044
Pollution control revenue bonds —
FFB loans	2,449	2,449
Georgia Power | Junior subordinated notes (5.00% to 6.25%) due 2057 to 2077
Pollution control revenue bonds —
Junior subordinated notes	270	270
Mississippi Power
Maturity
2019	0	125
2020	307
2021	270
2022	0
2023	0
Thereafter	950	680
Total long-term notes payable	1,250	1,705
Pollution control revenue bonds —
Pollution control revenue bonds	40	83
Total other long-term debt	310	353
Unamortized debt premium	29	36
Unamortized debt discount	(2)	(1)
Unamortized debt issuance expense	(8)	(7)
Total long-term debt	1,579	2,086
Amount due within one year	40	989
Long-term debt excluding amounts due within one year and held for sale	$ 1,539	$ 1,097
Percent capitalization	48.90%	44.10%
Cumulative preferred stock
Redeemable preferred stock	$ 0	$ 33
Total redeemable preferred stock - percent capitalization	0.00%	1.30%
Common Stockholders' Equity:
Common stock	$ 38	$ 38
Paid-in capital	4,546	4,529
Retained earnings	(2,971)	(3,205)
Accumulated other comprehensive loss	(4)	(4)
Total common stockholders' equity	$ 1,609	$ 1,358
Total common stockholders' equity - percent capitalization	51.10%	54.60%
Total Stockholders' Equity	$ 1,609	$ 1,358
Total Capitalization	$ 3,148	$ 2,488
Percent capitalization	100.00%	100.00%
Mississippi Power | Adjustable Rate Loans
Maturity
2018	$ 0	$ 900
2020	300	0
Mississippi Power | Pollution control revenue bonds due 2028
Pollution control revenue bonds —
Pollution control revenue bonds	0	43
Mississippi Power | Pollution control revenue bonds - variable rates (1.77 to 2.23% at 12/31/18) due 2019
Pollution control revenue bonds —
Pollution control revenue bonds	40	40
Mississippi Power | Plant Daniel revenue bonds (7.13%) due 2021
Pollution control revenue bonds —
Plant Daniel revenue bonds (7.13%) due 2021	270	270
Southern Company Gas
Maturity
2018	0	155
2019	350
2020	0
2021	330	330
2022	46	46
2023	400
Thereafter	3,134	3,134
Total long-term notes payable	4,160	4,315
Pollution control revenue bonds —
Total other long-term debt	1,325	1,225
Unamortized fair value adjustment of long-term debt	474	525
Unamortized debt discount	(19)	(17)
Total long-term debt	5,940	6,048
Amount due within one year	357	157
Long-term debt excluding amounts due within one year and held for sale	$ 5,583	$ 5,891
Percent capitalization	39.40%	39.50%
Common Stockholders' Equity:
Paid-in capital	$ 8,856	$ 9,214
Retained earnings	(312)	(212)
Accumulated other comprehensive loss	26	20
Total common stockholders' equity	$ 8,570	$ 9,022
Total common stockholders' equity - percent capitalization	60.60%	60.50%
Total Stockholders' Equity	$ 8,570	$ 9,022
Total Capitalization	$ 14,153	$ 14,913
Percent capitalization	100.00%	100.00%
Southern Company Gas | Long-term senior notes and debt maturing 2019
Maturity
2019	$ 300	$ 300
Southern Company Gas | Long-term senior notes and debt maturing 2023
Maturity
2023	350	350
Southern Company Gas | Gas facility revenue bonds - variable rate (1.71% at 12/31/17) due 2022
Pollution control revenue bonds —
Gas facility revenue bonds	0	47
Southern Company Gas | Gas facility revenue bonds - variable rate (1.71% at 12/31/17) due 2024 to 2033
Pollution control revenue bonds —
Gas facility revenue bonds	0	153
Southern Company Gas | First mortgage bonds — 4.70% due 2019
Pollution control revenue bonds —
First mortgage bonds	50	50
Southern Company Gas | First mortgage bonds - 5.80% due 2023
Pollution control revenue bonds —
First mortgage bonds	50	50
Southern Company Gas | First mortgage bonds — 2.66% to 6.58% due 2026 to 2057
Pollution control revenue bonds —
First mortgage bonds	$ 1,225	$ 925